[1] A most minute and exact description of the newly hatched larva of
_Chionobas Aëllo_ is given by the American entomologist, Samuel H.
Scudder. Ann. Soc. Ent. de Belgique, xvi., 1873.
[2] I am aware that this certainly cannot be said of philosophers
like Lotze or Herbert Spencer; but these are at the same time both
naturalists and philosophers.
[3] “Über die Artrechte des _Polyommatus Amyntas_ und _Polysperchon_.”
Stett. ent. Zeit. 1849. Vol. x. p. 177-182. [In Kirby’s “Synonymic
Catalogue of Diurnal Lepidoptera” _Plebeius Amyntas_ is given as a
synonym and _P. Polysperchon_ as a var. of _P. Argiades_ Pall. R.M.]
[4] “Die Arten der Lepidopteren-Gattung _Ino_ Leach, nebst einigen
Vorbemerkungen über Localvarietäten.” Stett. ent. Zeit. 1862. Vol.
xxiii. p. 342.
[5] [Eng. ed. W. H. Edwards has since pointed out several beautiful
cases of seasonal dimorphism in America. Thus _Plebeius Pseudargiolus_
is the summer form of _P. Violacea_, and _Phyciodes Tharos_ the summer
form of _P. Marcia_. See Edwards’ “Butterflies of North America,”
1868-79.]
[6] [Eng. ed. I learn by a written communication from Dr. Speyer that
two Geometræ, _Selenia Tetralunaria_ and _S. Illunaria_ Hüb., are
seasonally dimorphic. In both species the winter form is much larger
and darker.] [_Selenia Lunaria_, _S. Illustraria_, and some species of
_Ephyra_ (_E. Punctaria_ and _E. Omicronaria_) are likewise seasonally
dimorphic. For remarks on the case of _S. Illustraria_ see Dr. Knaggs
in Ent. Mo. Mag., vol. iii. p. 238, and p. 256. Some observations on
_E. Punctaria_ were communicated to the Entomological Society of London
by Professor Westwood in 1877, on the authority of Mr. B. G. Cole. See
Proc. Ent. Soc. 1877, pp. vi, vii. R.M.]
[7] [In 1860 Andrew Murray directed attention to the disguising colours
of species which, like the Alpine hare, stoat, and ptarmigan, undergo
seasonal variation of colour. See a paper “On the Disguises of Nature,
being an inquiry into the laws which regulate external form and colour
in plants and animals.” Edinb. New Phil. Journ., Jan. 1860. In 1873 I
attempted to show that these and other cases of “variable protective
colouring” could be fairly attributed to natural selection. See Proc.
Zoo. Soc., Feb. 4th, 1873, pp. 153-162. R.M.]
[8] [A phenomenon somewhat analogous to seasonal change of protecting
colour does occur in some Lepidoptera, only the change, instead of
occurring in the same individual, is displayed by the successive
individuals of the same brood. See Dr. Wallace on _Bombyx Cynthia_,
Trans. Ent. Soc. Vol. v. p. 485. R.M.]
[9] “Über den Einfluss der Isolirung auf die Artbildung.” Leipzig,
1872, pp. 55-62.
[10] [Mr. A. R. Wallace maintains that the obscurely coloured females
of those butterflies which possess brightly coloured males have been
rendered inconspicuous by natural selection, owing to the greater
need of protection by the former sex. See “Contributions to the
Theory of Natural Selection,” London, 1870, pp. 112-114. It is now
generally admitted that the underside of butterflies has undergone
protectional adaptation; and many cases of local variation in the
colour of the underside of the wings, in accordance with the nature of
the soil, &c., are known. See, for instance, Mr. D. G. Rutherford on
the colour-varieties of _Aterica Meleagris_ (Proc. Ent. Soc. 1878, p.
xlii.), and Mr. J. Jenner Weir on a similar phenomenon in _Hipparchia
Semele_ (_loc. cit._ p. xlix.) R.M.]
[11] [The fact that moths which, like the Geometræ, rest by day with
the wings spread out, are protectively marked on the _upper_ side,
fully corroborates this statement. R.M.]
[12] “Über die Einwirkung verschiedener, während der
Entwicklungsperioden angewendeter Wärmegrade auf die Färbung und
Zeichnung der Schmetterlinge.” A communication to the Society of
Natural Science of Steiermark, 1864.
[13] See Exp. 9, Appendix I.
[14] See Exp. 11, Appendix I.
[15] See Exps. 4, 9, and 11, Appendix I.
[16] It seems to me very necessary to have a word expressing whether a
species produces one, two, or more generations in the year, and I have
therefore coined the expression _mono-_, _di-_, and _polygoneutic_ from
γονεύω, I produce.
[17] [Eng. ed. In the German edition, which appeared in 1874, I was
not able to support this hypothesis by geographical data, and could
then only ask the question “whether in the most northern portion of
its area of distribution, appears in two or only in one generation?”
This question is now answered by the Swedish Expedition to the Yenisei
in 1876. Herr Philipp Trybom, one of the members of this expedition,
observed _A. Levana_ at the end of June and beginning of July, in
the middle of Yenisei, in 60°-63° N. (Dagfjärilar från Yenisei in
Översigt ap k. Vertensk. Akad. Förhandlingon, 1877, No. 6.) Trybom
found _Levana_ at Yenisk on June 23rd, at Worogova (61° 5´) on July
3rd, at Asinova (61° 25´) on July 4th, at Insarowa (62° 5´) on July
7th, and at Alinskaja (63° 25´) on July 9th. The butterflies were
especially abundant at the beginning of June, and were all of the
typical _Levana_ form. Trybom expressly states, “we did not find a
single specimen which differed perceptibly from Weismann’s Figs. 1 and
2 (‘Saison-Dimorphismus’ Taf. I.).”
The Swedish expedition soon left the Yenisei, and consequently was not
able to decide by observations whether a second generation possessing
the _Prorsa_ form appeared later in the summer. Nevertheless, it may be
stated with great probability that this is not the case. The districts
in which _Levana_ occurs on the Yenisei have about the same isotherm as
Archangel or Haparanda, and therefore the same summer temperature. Dr.
Staudinger, whose views I solicited, writes to me:--“In Finnmark (about
67° N.) I observed no species with two generations; even _Polyommatus
Phlæas_, which occurs there, and which in Germany has always two, and
in the south, perhaps, three generations, in Finnmark has only one
generation. A second generation would be impossible, and this would
also be the case with _Levana_ in the middle of Yenisei. I certainly
have _Levana_ and _Prorsa_ from the middle of Amur, but _Levana_ flies
there at the end of May, and the summers are very warm.” The middle of
Amur lies, moreover, in 50° N. lat., and therefore 10°-13° south of the
districts of the Yenisei mentioned.
It must thus be certainly admitted that on the Yenisei _A. Levana_
occurs only in the _Levana_ form, and that consequently this species
is at the present time, in the northernmost portion of its area of
distribution, in the same condition as that in which I conceive
it to have been in mid Europe during the glacial period. It would
be of the greatest interest to make experiments in breeding with
this single-brooded _Levana_ from the Yenisei, i.e., to attempt to
change its offspring into the _Prorsa_ form by the action of a high
temperature. If this could not be accomplished it would furnish a
confirmation of my hypothesis than which nothing more rigorous could be
desired.]
[18] See Exp. 10, Appendix I.
[19] When Dorfmeister remarks that hibernating pupæ which, at an
early stage “were taken for development into a room, or not exposed
to any cold, gave dwarfed, weakly and crippled,” or otherwise damaged
butterflies, this is entirely attributable to the fact that this able
entomologist had neglected to supply the necessary moisture to the
warm air. By keeping pupæ over water I have always obtained very fine
butterflies.
[20] [For other remarkable cases of sexual dimorphism (not _antigeny_
in the sense used by Mr. S. H. Scudder, Proc. Amer. Acad., vol. xii.
1877, pp. 150-158) see Wallace “On the Phenomena of Variation and
Geographical Distribution, as illustrated by the Papilionidæ of the
Malayan Region,” Trans. Linn. Soc., vol. xxv. 1865, pp. 5-10. R.M.]
[21] [Eng. ed. Dimorphism of this kind has since been made known: the
North American _Limenitis Artemis_ and _L. Proserpina_ are not two
species, as was formerly believed, but only one. Edwards bred both
forms from eggs of _Proserpina_. Both are single-brooded, and both have
males and females. The two forms fly together, but _L. Artemis_ is much
more widely distributed, and more abundant than _L. Proserpina_. See
“Butterflies of North America,” vol. ii.]
[22] [Eng. ed. Edwards has since proved experimentally that by the
application of ice a large proportion of the pupæ do indeed give rise
to the var. _Telamonides_. He bred from eggs of _Telamonides_ 122 pupæ,
which, under natural conditions, would nearly all have given the var.
_Marcellus_. After two months’ exposure to the low temperature there
emerged from August 24th to October 16th, fifty butterflies, viz.
twenty-two _Telamonides_, one intermediate form between _Telamonides_
and _Walshii_, eight intermediate forms between _Telamonides_ and
_Marcellus_ more nearly related to the former, six intermediate forms
between _Telamonides_ and _Marcellus_, but more closely resembling the
latter, and thirteen _Marcellus_. Through various mishaps the action of
the ice was not complete and equal. See the “Canadian Entomologist,”
1875, p. 228. In the newly discovered case of _Phyciodes Tharos_ also,
Edwards has succeeded in causing the brood from the winter form to
revert, by the application of ice to this same form. See Appendix II.
for a _résumé_ of Edwards’ experiments upon both _Papilio Ajax_ and
_Phyciodes Tharos_. R.M.]
[23] Thus from eggs of _Walshii_, laid on April 10th, Edwards obtained,
after a pupal period of fourteen days, from the 1st to the 6th of June,
fifty-eight butterflies of the form _Marcellus_, one of _Walshii_, and
one of _Telamonides_.
[24] [The word ‘Amixie,’ from the Greek ἀμιξία, was first adopted
by the author to express the idea of the prevention of crossing by
isolation in his essay “Über den Einfluss der Isolirung auf die
Artbildung,” Leipzig, 1872, p. 49. R.M.]
[25] [Eng. ed. In 1844, Boisduval maintained this relationship of the
two forms. See Speyer’s “Geographische Verbreit. d. Schmetterl.,” i. p.
455.]
[26] According to a written communication from Dr. Staudinger, the
female _Bryoniæ_ from Lapland are never so dusky as is commonly the
case in the Alps, but they often have, on the other hand, a yellow
instead of a white ground-colour. In the Alps, yellow specimens are not
uncommon, and in the Jura are even the rule.
[27] [According to W. F. Kirby (Syn. Cat. Diurn. Lepidop.), the species
is almost cosmopolitan, occurring, as well as throughout Europe, in
Northern India (var. _Timeus_), Shanghai (var. _Chinensis_), Abyssinia
(var. _Pseudophlæas_), Massachusetts (var. _Americana_), and California
(var. _Hypophlæas_). In a long series from Northern India, in my own
collection, all the specimens are extremely dark, the males being
almost black. R.M.]
[28] [Eng. ed. From a written communication from Dr. Speyer, it appears
that also in Germany there is a small difference between the two
generations. The German summer brood has likewise more black on the
upper side, although seldom so much as the South European summer brood.]
[29] [Assuming that in all butterflies similar colours are produced by
the same chemical compounds. R.M.]
[30] [Mr. H. W. Bates mentions instances of local variation in colour
affecting many distinct species in the same district in his memoir “On
the Lepidoptera of the Amazon Valley;” Trans. Linn. Soc., vol. xxiii.
Mr. A. R. Wallace also has brought together a large number of cases
of variation in colour according to distribution, in his address to
the biological section of the British Association at Glasgow in 1876.
See “Brit. Assoc. Report,” 1876, pp. 100-110. For observations on the
change of colour in British Lepidoptera according to distribution see
papers by Mr. E. Birchall in “Ent. Mo. Mag.,” Nov., 1876, and by Dr.
F. Buchanan White, “Ent. Mo. Mag.,” Dec., 1876. The colour variations
in all these cases are of course not _protective_ as in the well-known
case of _Gnophos obscurata_, &c. R.M.]
[31] See Figs. 10 and 14, 11 and 15, Plate I.
[32] “On the Origin and Metamorphoses of Insects,” London, 1874.
[33] I at first thought of designating the two forms of cyclical or
homochronic heredity as ontogenetic- and phyletic-cyclical heredity.
The former would certainly be correct; the latter would be also
applicable to alternation of generation (in which actually two or
more phyletic stages alternate with each other) but not to all those
cases which I attribute to heterogenesis, in which, as with seasonal
dimorphism, a series of generations of _the same_ phyletic stage
constitute the point of departure.
[34] When Meyer-Dürr, who is otherwise very accurate, states in his
“Verzeichniss der Schmetterlinge der Schweiz,” (1852, p. 207), that the
winter and summer generations of _P. Ægeria_ differ to a small extent
in the contour of the wings and in marking, he has committed an error.
The characters which this author attributes to the summer form are
much more applicable to the female sex. There exists in this species a
trifling sexual dimorphism, but no seasonal dimorphism.
[35] P. C. Zeller, “Bemerkungen über die auf einer Reise nach Italien
und Sicilien gesammelten Schmetterlingsarten.” Isis, 1847, ii.-xii.
[36] “Isoporien der europäischen Tagfalter.” Stuttgart, 1873.
[37] [Trans. Linn. Soc., vol. xxv. 1865, p. 9. R.M.]
[38] It is certainly preferable to make use of the expression
“metagenesis” in this special sense instead of introducing a new one.
As a general designation, comprehending metagenesis and heterogenesis,
there will then remain the expression “alternation of generation,” if
one does not prefer to say “cyclical propagation.” The latter may be
well used in contradistinction to “metamorphosis.”
[39] _Loc. cit._ chap. iv.
[40] The idea that alternation of generation is derived from
polymorphism (not the reverse, as usually happens; i.e. polymorphism
from alternation of generation) is not new, as I find whilst correcting
the final proof. Semper has already expressed it at the conclusion of
his interesting memoir, “Über Generationswechsel bei Steinkorallen,”
&c. See “Zeitschrift f. wiss. Zool.” vol. xxii. 1872.
[41] See my essay “Über den Einfluss der Isolirung auf die Artbildung.”
Leipzig, 1872.
[42] [In the case of monogoneutic species which, by artificial
‘forcing,’ have been made to give two generations in the year, it has
generally been found that the reproductive system has been imperfectly
developed in the second brood. A minute anatomical investigation of the
sexual organs in the two broods of seasonally dimorphic insects would
be of great interest, and might lead to important results. R.M.]
[43] “Grundzüge der Zoologie.” 2nd ed. Leipzig, 1872. Introduction.
[44] With reference to this subject, see the discussion by the Belgian
Entomological Society, Brussels, 1873.
[45] P. E. Müller, “Bidrag til Cladocerners Fortplantingshistorie,”
1868.
[46] Sars, in “Förhandlinger i Videnskabs Selskabet i Christiania,”
1873, part i.
[47] [Eng. ed. Recent researches on alternation of generation in
the Daphniacea have convinced me that _direct_ action of external
conditions does not in these cases come into consideration, but only
_indirect_ action.]
[48] See my memoir, “Über Bau und Lebenserscheinungen der _Leptodora
hyalina_,” Zeitschrift f. wiss. Zool., vol. xxiv. part 3, 1874.
[49] Stettin. entom. Zeit., vol. xviii. p. 83, 1857.
[50] Compt. Rend., vol. lxxvii. p. 1164, 1873.
[51] [“Accidental” in the sense of our being in ignorance of the laws
of variation, as so frequently insisted upon by Darwin. R.M.]
[52] [Eng. ed. Since this was written I have studied the ornamental
colours of the _Daphniidæ_; and, as a result, I no longer doubt that
sexual selection plays a very important part in the marking and
colouring of butterflies. I by no means exclude both transforming
factors, however; it is quite conceivable, on the contrary, that a
change produced directly by climate may be still further increased by
sexual selection. The above given case of _Polyommatus Phlæas_ may
perhaps be explained in this manner. That sexual selection plays a
part in butterflies, is proved above all by the odoriferous scales and
tufts of the males discovered by Fritz Müller.] [For remarks on the
odours emitted by butterflies and moths, see Fritz Müller in “Jena.
Zeit. f. Naturwissen.,” vol. xi. p. 99; also “Notes on Brazilian
Entomology,” Trans. Ent. Soc. 1878, p. 211. The odoriferous organs
of the female _Heliconinæ_ are fully described in a paper in “Zeit.
f. Wissen. Zool.,” vol. xxx. p. 167. The position of the scent-tufts
in the sphinx-moths is shown in Proc. Entom. Soc. 1878, p. ii. Many
British moths, such as _Phlogophora meticulosa_, _Cosmia trapezina_,
&c. &c., have tufts in a similar position. The fans on the feet of
_Acidalia bisetata_, _Herminia barbalis_, _H. tarsipennalis_, &c., are
also probably scent organs. A large moth from Jamaica, well known to
possess a powerful odour when alive (_Erebus odorus_ Linn.), has great
scent-tufts on the hind legs. For the application of the theory of
sexual selection to butterflies, see, in addition, to Darwin’s “Descent
of Man,” Fritz Müller in “Kosmos,” vol. ii. p. 42; also for January,
1879, p. 285; and Darwin in “Nature,” vol. xxi. January 8th, 1880, p.
237. R.M.]
[53] Nägeli, “Entstehung und Begriff der naturhistorischen Art,”
Munich, 1865, p. 25. The author interprets the facts above quoted in a
quite opposite sense, but this is obviously erroneous.
[54] See my essay, “Über den Einfluss der Isolirung auf die
Artbildung.” Leipzig, 1872.
[55] [Eng. ed. In the summer of 1877, Dr. Hilgendorf again investigated
the Steinheim fossil shells, and found his former statements to be
completely confirmed. At the meeting of the German Naturalists and
Physicists at Munich, in 1877, he exhibited numerous preparations,
which left no doubt that the chief results of his first research were
correct, and that there have been deposited a series of successively
derived species together with their connecting intermediate forms.]
[56] See my essay, “Über die Berechtigung der Darwin’schen Theorie.”
Leipzig, 1868.
[57] I expressly insist upon this here, because the notice of
Askenasy’s thoughtful essay which I gave in the “Archiv für
Anthropologie” (1873) has frequently been misunderstood.
[58] The experiments upon _Papilio Ajax_ and _Phyciodes Tharos_,
described in this Appendix, were made by Mr. W. H. Edwards (see his
“Butterflies of North America;” also the “Canadian Entomologist,” vol.
vii. p. 228-240, and vol. ix. p. 1-10, 51-5, and 203-6); and I have
added them, together with some hitherto unpublished results, to Dr.
Weismann’s Essay, in order to complete the history of the subject of
seasonal dimorphism up to the present time.--R.M.
[59] This is a striking illustration of the diversity of individual
constitution so frequently insisted on by Dr. Weismann in the foregoing
portion of this work.
[60] The reader who wishes to acquire a detailed knowledge of the
different varieties of this butterfly, of which a very large number
are known, must consult the plates and descriptions in Edwards’
“Butterflies of North America,” vol. ii.
[61] Mr. Edwards has shown also that _Argynnis Myrina_ can lay fertile
eggs when but a few hours out of the chrysalis. Canad. Ent., September,
1876, vol. viii. No. 9.
[62] Mr. Edwards remarks that the habit of becoming lethargic is of
great service to a digoneutic species in a mountain region where it is
exposed to sharp changes of temperature. “If the fate of the species
depended on the last larval brood of the year, and especially if the
larvæ must reach a certain stage of growth before they were fitted to
enter upon their hibernation, it might well happen that now and then an
early frost or a tempestuous season would destroy all the larvæ of the
district.”
[63] Compare this with Weismann’s remarks, pp. 19-22, and 53.
[64] See Canad. Ent., vol. ix. p. 69.
[65] Figures of the different forms of this species are given in vol.
i. of Edward’s “Butterflies of North America.”
[66] Only the species of _Smerinthus_ can be made to lay eggs regularly
in confinement; _Macroglossa Stellatarum_ laid a number in a large
gauze-covered breeding-cage; the species of _Deilephila_ could not be
induced to lay more than single ones in such a cage. From species of
_Chærocampa_ also I never obtained but a few eggs, and from _Sphinx_
and _Acherontia_ never more than single ones.
[67] [Eng. ed. Since the appearance of the German edition of this
work, numerous descriptions of the young stages of caterpillars have
been given, but in all cases without representing the relationship of
the forms.] [In the excellent figures of larvæ at various stages of
growth, given in some of the more recent works on Lepidoptera, there
will be found much material which may be regarded as a contribution to
the field of research entered on by the author in the present essay,
_i.e._ the ontogeny and comparative morphology of larval markings,
although it is much to be regretted that the figures and descriptions
have not been given from this point of view. In his “Butterflies of
North America,” for example, W. H. Edwards figures the young as well
as the adult larvæ of species of _Apatura_, _Argynnis_, _Libythea_,
_Phyciodes_, _Limenitis_, _Colias_, _Papilio_, &c. Burmeister, in his
recently published “Lépidoptères de la République Argentine,” figures
the young stages of species of _Caligo_, _Opsiphanes_, _Callidryas_,
_Philampelus_, &c. Messrs. Hellins and Buckler have figured and
described the early stages of large numbers of the caterpillars of
British Lepidoptera, but their figures remain unpublished. The larvæ
of many of our native species belonging to the genera _Liparis_,
_Tæniocampa_, _Epunda_, _Cymatophora_, _Calocampa_, &c., are dull when
young, but become brightly coloured at the last moult. Such changes
of colour are probably associated with some change, either in the
habits or in the environment; and a careful study of the ontogenetic
development of such species in connection with their life-history would
furnish results of great value to the present inquiry. The same remarks
apply to those _Noctuæ_ larvæ which are brightly coloured in their
young stages, and become dull when adult.
Among other papers which may be considered as contributions to
the present subject, I may mention the following:--In 1864 Capt.
Hutton published a paper, “On the Reversion and Restoration of the
Silkworm, Part II.” (Trans. Ent. Soc. 1864, p. 295), in which he
describes the various stages of development of several species of
_Bombycidæ_. In 1867 G. Semper published accounts of the early stages
of several Sphinx-larvæ (“Beiträge zur Entwicklungsgeschichte einiger
ostasiatischer Schmetterlinge,” Verhandl. k.k. Zoolog.-botan. Gesell.
in Wien, vol. xvii.). The question as to the number of claspers in
young _Noctuæ_ larvæ has been raised in notes by Dr. F. Buchanan White
(“Ent. Mo. Mag.,” vol. v. p. 204) and B. Lockyer (“Entomologist,” 1871,
p. 433). A valuable paper, “On the Embryonic Larvæ of Butterflies,”
was published in 1871 by S. H. Scudder (“Ent. Mo. Mag.,” vol. viii. p.
122). For remarks on the development of the larva of _Papilio Merope_,
see J. P. Mansel Weale in Trans. Ent. Soc., 1874, p. 131, and Pl. I.;
also this author on the young stages of the larva of _Gynanisa Isis_,
Trans. Ent. Soc., 1878, p. 184. For an account of the development of
the larvæ of certain North American species of _Satyrus_, see W. H.
Edwards in the “Canadian Entom.,” vol. xii. p. 21. Mr. P. H. Gosse’s
recent description of the newly hatched caterpillar of _Papilio
Homerus_ (Proc. Ent. Soc. 1879, p. lv), furnishes a good illustration
of the value of studying the ontogeny. The natural affinities of
the _Papilionidæ_ were at one time much disputed, some systematists
placing this family at the head of the Lepidoptera, and others
regarding them as being more closely allied to the moths. Mr. Gosse’s
observation tends to confirm the latter view, now generally received by
Lepidopterists, since he states that the larva in question “suggests
one of the great _Saturniadæ_, such as _Samia Cecropia_.” Mr. Scudder,
in the paper above referred to, adopts an analogous argument to show
the close relationship between the _Papilionidæ_ and _Hesperidæ_. R.M.]
[68] [Mr. A. G. Butler has recently furnished a good illustration of
the danger of classifying Lepidoptera according to the affinities of
the perfect insects only, in his paper, “On the Natural Affinities of
the Lepidoptera hitherto referred to the Genus _Acronycta_ of authors,”
Trans. Ent. Soc. 1879, p. 313. If the author’s views are ultimately
accepted, the species at present grouped under this genus will be
distributed among the _Arctiidæ_, _Liparidæ_, _Notodontidæ_, and
_Noctuæ_. Mr. Butler’s determination of the affinities of the species
supposed to belong to the genus mentioned, is based chiefly upon a
comparative examination of the larvæ, and this is far more likely to
show the true blood-relationship of the species than a comparison of
the perfect insects only. A study of the comparative ontogeny can alone
give a final answer to this question. R.M.]
[69] [In his recent revision of the _Sphingidæ_, Mr. A. G. Butler
(Trans. Zoo. Soc., vol. ix. part x.) retains Walker’s arrangement. R.M.]
[70] The deposition of black pigment may commence immediately before
ecdysis.
[71] [Mr. Herbert Goss states (Proc. Ent. Soc. 1878, p. v.) that
according to his experience, the green and brown varieties of _C.
Porcellus_ (erroneously printed as _Elpenor_ in the passage referred
to) are about equally common, the former colour not being in any way
confined to young larvæ. Mr. Owen Wilson in his recent work, “The Larvæ
of British Lepidoptera and their food-plants,” figures (Pl. VIII.,
Figs. 3 and 3a) the two forms, both apparently in the adult state.
During the years 1878-79, my friend, Mr. J. Evershed, jun., took five
of these full-grown larvæ in Surrey, one of these being the green
variety. In order to get more statistics on this subject, I applied
this year (1880) to Messrs. Davis of Dartford, who informed me that
among 18-20 adult caterpillars of _Porcellus_ in their possession,
there was only one green specimen. R.M.]
[72] I unite the genera _Pergesa_ and _Darapsa_ of Walk. with
_Chærocampa_, Dup.; the first appears to me to be quite untenable,
since it is impossible that two species, of which the caterpillars
agree so completely as those of _C. Elpenor_ and _Porcellus_, can
be located in different genera. _Porcellus_ indeed was referred to
the genus _Pergesa_ because of its different contour of wings, an
instance which distinctly shows how dangerous it is to attempt to found
Lepidopterous genera without considering the caterpillars. The genus
_Darapsa_ also appears to me to be of very doubtful value, and in any
case requires further confirmation with respect to the larval forms.
[73] [Mr. A. G. Butler (Trans. Zoo. Soc., vol. ix., part. x., 1876)
gives a list of about eighty-four species of _Chærocampa_, and sixteen
of _Pergesa_, besides numerous other species belonging to several
genera placed between _Chærocampa_ and _Pergesa_. Of _Darapsa_, he
states “that this genus was founded upon most heterogeneous material,
the first three species being referable to Hübner’s genus _Otus_, the
fifth to Walker’s genus _Diodosida_, the sixth and eighth to the genus
_Daphnis_ of Hübner, the seventh, ninth, and tenth to _Chærocampa_ of
Duponchel; there therefore remains only the fourth species, allied to
_Chærocampa_, but apparently sufficiently distinct.” The species still
retained in the genus _Darapsa_ is _D. rhodocera_, Wlk., from Haiti.
R.M.]
[74] [_Otus Syriacus_ of Butler’s revision. R.M.]
[75] Abbot and Smith. “The Natural History of the rarer Lepidopterous
Insects of Georgia, collected from the observations of John Abbot, with
the plants on which they feed.” London, 1797, 2 vols. fol.
[76] [_Otus Chœrilus_ and _O. Myron_ of Butler’s revision. R.M.]
[77] [To this group may also be added _Ampelophaga Rubiginosa_,
Ménétriés, from China and Japan, the caterpillar of which, having the
distinct subdorsal line without any trace of eye-spots, is figured by
Butler (_loc. cit._, Pl. XCI., Fig. 4). This author also gives a figure
of another species belonging to the subfamily _Chærocampinæ_ (Pl. XC.,
Fig. 11), viz. _Acosmeryx Anceus_, Cram., from Amboina, Java, Silhet,
and S. India; the caterpillar is green, with seven oblique yellow
stripes along the sides, and a very conspicuous white subdorsal line
with a red border above. As there are no eye-spots, this species may
be referred to the present group provisionally, although its general
marking is very distinct from that of the _Chærocampa_ group. R.M.]
[78] [Eng. ed. Dr. Staudinger has since obtained the caterpillar of _C.
Alecto_ from Beyrout; it possesses “a very distinct subdorsal line,
and on the fourth segment a beautiful eye-spot, which is repeated with
gradual diminution to segments 7-8”.]
[79] Figured in “A Catalogue of Lepidopterous Insects in the Museum
of the East India Company,” by Thomas Horsfield and Frederick Moore.
London, 1857. Vol. i., Pl. XI.
[80] Figured in Trans. Ent. Soc., New Series, vol. iv., Pl. XIII.
[81] _Ibid._
[82] [The following species figured by Butler (_loc. cit._ Pls. XC.
and XCI.) appear to belong to the second group--_Chærocampa Japonica_,
Boisd., which is figured in two forms, one brown, and the other green.
The former has two distinct ocelli on the fourth and fifth segments,
and a distinct rudiment on the sixth, whilst the subdorsal line extends
from the second eye-spot to the caudal horn, and beneath this line
the oblique lateral stripes stand out conspicuously in dark brown on
a lighter ground. The ocelli are equally well developed on the fourth
and fifth segments in the green variety, the subdorsal line commencing
on the sixth segment, and extending to the caudal horn; there is no
trace of a third eye-spot, nor are there any oblique lateral stripes;
the insect is almost the exact counterpart of _C. Elpenor_ in its
fourth stage. (See Fig. 21, Pl. IV.) _Pergesa Mongoliana_, Butl., is
brown, without a trace of the subdorsal line except on the three front
segments, and with only one large eye-spot on the fourth segment.
_Chærocampa Lewisii_, Butl., from Japan, is likewise figured in two
forms. The brown variety has the subdorsal line on the three front
segments only, distinct ocelli on the fourth and fifth segments, and
gradually diminishing rudiments on the remaining segments. The green
form appears to be transitional between the present and the third
group, as it possesses a distinct, but rudimentary eye-spot on the
third segment, besides the fully developed ones on the fourth and
fifth, and very conspicuous, but gradually decreasing repetitions
of rudimentary ocelli on segments 6-10. To this group may be added
_Chærocampa Aristor_, Boisd., the caterpillar of which is figured by
Burmeister (Lép. Rép. Arg., Pl. XV., Fig. 4) in the characteristic
attitude of alarm, with the front segments retracted, and the ocelli on
the fourth segment prominently exposed. The subdorsal line is present
in this species. Burmeister also figures two of the early stages (Pl.
XV., Fig. 7, A and B), and describes the complete development of
_Philampelus Labruscæ_, another species belonging to the subfamily
_Chærocampinæ_. The earliest stage (3-4 days old) is simple green, with
no trace of any marking except a black spot on each side of the fourth
segment, the position of the future ocelli. A curved horn is present
both in this stage and the following one, during which the caterpillar
is still green, but now has seven oblique red lateral stripes. The
caudal horn is shed at the second moult, after which the colour becomes
darker, the adult larva (figured by Madame Mérian, in her work on
Surinam, pl. 34 and Sepp., pl. 32) being mottled brown. In addition to
the ocellus on the fourth segment, there is another slightly larger
on the eleventh segment, so that this species may perhaps be another
transition to the third group; but our knowledge is still too imperfect
to attempt to generalize with safety. R.M.]
[83] Cat. Lep. Ins. East Ind. Comp., Pl. XIII. [Figured also by Butler
(=_Chæerocampa Silhetensis_, Walker), _loc. cit._ Pl. XCII., Fig. 8.
R.M.]
[84] Cat. Lep. Ins. East Ind. Comp., Pl. XIII. [Figured also by Butler,
_loc. cit._ Pl. XCI., Fig. 1. R.M.]
[85] Horsfield and Moore, _loc. cit._ Pl. X.
[86] _Ibid._ [=_Pergesa Acteus_, Walker. R.M.]
[87] [Figured also by Burmeister, _loc. cit._ Pl. XV., Fig. 3. R.M.]
[88] Horsfield and Moore, _loc. cit._, Pl. XI.
[89] To be accurate this should be designated the infra-spiracular
line; but this term cannot be well applied except in cases where
there is also a supra-spiracular line, as, for instance, in _Anceryx
(Hyloicus) Pinastri_.
[90] Upon this fact obviously depends the statement of that extremely
accurate observer Rösel, that the caterpillar of _Euphorbiæ_ is but
very slightly variable (“Insektenbelustigungen,” Bd. iii. p. 36). I
formerly held the same opinion, till I convinced myself that this
species is very constant in some localities, but very variable in
others. It appears that local influences make the caterpillar variable.
[91] The green is considerably too light in Fig. 45.
[92] “Die Pflanzen und Raupen Deutschlands.” Berlin, 1860, p. 83.
[93] Fig. 62, Pl. VII., is copied from Boisduval.
[94] The fading of the red anteriorly has not been represented in the
figure.
[95] [The caterpillar of _Deilephila Euphorbiarum_, figured by
Burmeister (Lép. Rép. Arg., Pl. XVI, Fig. 1) belongs to this stage.
R.M.]
[96] [In concluding this account of the _Chærocampinæ_ I may call
attention to the following species, which have since been figured by
Burmeister:--_Pachylia Ficus_, Linn. (_loc. cit._ Pl. XIV., Figs. 1
and 2); during the three first stages the larva is uniformly green,
with a yellow subdorsal line, and below this ten oblique yellow
stripes slanting away from the head; after the third moult the colour
completely changes, the whole area of the body being divided into two
distinct portions by the subdorsal line, above which the colour is
red, and underneath of a pale green; the oblique stripes have almost
disappeared; no occelli nor annuli are present. _Pachylia Syces_, Hübn.
(_loc. cit._ Fig. 3); very similar to the last species in its young
stages (figured also by Mérian, Surin. pl. 33). _Philampelus Vitis_,
Linn. (_loc. cit._ Figs. 4 and 5); two stages represented; between
first and second moults green, with oblique paler stripes slanting in
same direction as in _Pachylia_, and each one containing a red streak
surrounding the spiracle. When adult, the ground-colour is yellow above
and green beneath, the whole surface being mottled with deep black and
red transverse markings; the oblique stripes whitish, bordered with
black at their lower extremities (figured also by Mérian, pls. 9 and
39). _Philampelus Anchemolus_, Cram. (_loc. cit._ Pl. XV., Fig. 1;
Mérian, pl. 47); green when young, with seven oblique red stripes; when
adult, uniformly brown, with seven pale yellow lateral markings, the
first four of which are spots, and the remainder broad oblique stripes
slanting forwards. _Philampelus Labruscæ_, (see note 82, p. 195). R.M.]
[97] [_Mimas Tiliæ_ of Butler’s revision. The author states that this
genus is “easily distinguished from _Laothoë_ by the form of the wings,
the outer margin of secondaries deeply excavated below the apex, and
the secondaries narrow and not denticulated.” Here again we have a
clashing of the results arrived at by a study of the ontogeny of the
larvæ, on the one hand, and the founding of genera on the characters of
the imagines only, on the other. Of the three species discussed by Dr.
Weismann, Mr. Butler, following other authors, refers _Tiliæ_ to the
genus _Mimas_, _Populi_ to _Laothoë_, and _Ocellatus_ to _Smerinthus_.
It is to be hoped that when our knowledge of the developmental history
of larvæ is more complete in all groups, a reconciliation between the
results of the biological investigator and the pure systematist will be
brought about, so that a genus may not, as at present, have such very
different values when regarded from these two points of view. R.M.]
[98] The caterpillar is thus figured by Rösel.
[99] [In 1879 Mr. E. Boscher found about thirty full-grown caterpillars
of this species in the neighbourhood of Twickenham, ten to twelve
of which were feeding on _Salix viminalis_, and the remainder, from
a locality not far distant, on _Salix triandra_. The whole of the
specimens taken on the plant first named, had the red-brown spots above
and below the oblique stripes more or less completely developed, as
I myself had an opportunity of observing. In these spotted specimens
the ground-colour was bright yellowish-green, and in the others this
colour was dull whitish-green above, passing into bluish-green below.
Should these observations receive wider confirmation, it would be
fair to conclude that this species is now in two states of phyletic
development, the more advanced stage being represented by the brighter
spotted variety. (See also Proc. Ent. Soc. 1879, p. xliv.). Mr. Peter
Cameron has recently suggested (Trans. Ent. Soc. 1880, p. 69) that the
reddish-brown spots on the _Smerinthus_ caterpillars may serve for
purposes of disguise, as they closely resemble, both in colour and
form, certain galls (_Phytoptus_) of the food-plants of these species.
If this view be admitted, these spots must be considered as a new
character, now being developed by natural selection. The variation in
the ground-colour of the two forms of _S. Ocellatus_ may possibly be
phytophagic, but this can only be decisively settled by a series of
carefully conducted experiments. R.M.]
[100] “Insekten-Belustigungen,” Suppl. Pl. 38, Fig. 40.
[101] “Catalogue of Lepidop.” British Museum. [Butler divides the
subfamily _Smerinthinæ_ into 17 genera, containing 79 species, viz.
_Metamimas_, 2; _Mimas_, 4; _Polyptychus_, 7; _Lophostethus_, 1;
_Sphingonæpiopsis_, 1; _Langia_, 2; _Triptogon_, 23; _Laothoë_, 2;
_Cressonia_, 3; _Paonias_, 2; _Calasymbolus_, 5; _Smerinthus_, 5;
_Pseudosmerinthus_, 2; _Daphnusa_, 4; _Leucophlebia_, 5; _Basiana_, 10;
_Cæquosa_, 1. R.M.]
[102] “Cabinet Orient. Entom.,” p. 13, Pl. VI., Fig. 2. [Butler places
this species doubtfully among the _Sphinginæ_. R.M.]
[103] “Catalogue of the Lepidop. Insects of the E.I. Co.,” by Horsfield
and Moore. Pl. VIII., Fig. 6.
[104] [The larvæ of four other species of this subfamily have since
been made known through Mr. Butler’s figures. _Smerinthus Tatarinovii_,
Ménetriés (_loc. cit._ Pl. XC., Fig. 16), from Japan, is “pale
sea-green, tuberculated with white, with seven lateral, oblique,
crimson-edged white stripes.” There is no trace of the subdorsal line
shown in the figure, so that this species thus appears to be in the
third phyletic stage of development. _Smerinthus Planus_, Walker, from
China (_loc. cit._ Pl XCII., Fig. 11), is “pale green, with white or
yellow lateral stripes.” A trace of the subdorsal line remains on
the front segments, thus showing that the species is in the second
phyletic stage of development. _Triptogon Roseipennis_, Butler, from
Hakodadi (_loc. cit._ Pl. XCI., Fig. 6), is represented as yellow,
with seven oblique white stripes, with large irregular triangular red
spots extending from the anterior edge of the stripes, nearly across
each segment. It is probably in the third phyletic stage. The Indian
_Polyptychus Dentatus_, Cramer (_loc. cit._ Pl. XCI., Fig. 10), is
“bluish-green at the sides, with oblique purple stripes, with a broad,
dorsal, longitudinal, golden-green band, bordered by subtriangular
purple spots, one above each stripe.” The dorsal band is bordered by
coloured stripes, which may be the subdorsal lines; but the position
in which it is figured, and its very different mode of coloration,
make it very difficult to compare satisfactorily with the foregoing
species. The genus _Ambulyx_ is closely allied to the _Smerinthinæ_,
and the two following species may be here mentioned: _A. Gannascus_,
Stoll, figured by Burmeister (_loc. cit._ Pl. XIII., Fig. 5), is green,
with a yellow subdorsal line, and seven oblique white lateral stripes,
edged with red. _A. Liturata_, Butl. (_loc. cit._ Pl. XCI., Fig. 2), is
yellowish-green above, passing into bluish-green below. The subdorsal
is present on the three front segments, and is followed by a row of
white, elongated patches, one on each segment, these being the upper
portions of a row of lateral oblique stripes. The thickened upper
extremities of the latter are edged with red, and their arrangement
is very suggestive of their having arisen from the breaking up of a
subdorsal line. R.M.]
[105] [Butler catalogues 43 species of this genus. R.M.]
[106] The deposition of eggs was accomplished by the insect laying hold
of the point of a twig with its legs during flight, and curving its
abdomen upwards against a leaf, the wings being kept vibrating. The egg
is instantaneously fastened to the leaf. This operation is repeated
from twice to four times successively, the moth then hovering over and
sucking at the flowers for some time. The eggs exactly resemble in
colour the young green buds of _Galium_.
[107] [Figures of a remarkable case of gynandromorphism in a butterfly
(_Cirrochroa Aoris_, Doubl.) have recently been published by Prof.
Westwood (Trans. Ent. Soc. 1880, p. 113). On the right fore- and
hind-wings of a male specimen there are patches of female colouring,
thus bearing out in a very striking manner the above views concerning
the non-fusibility of characters (in this case sexual) which have been
long fixed. Complete (_i.e._ half-and-half) gynandromorphism is not
uncommon in butterflies. R.M.]
[108] [I have long held the opinion that the di- and trimorphism
displayed by certain butterflies has originated through polymorphism
from ordinary variability. I will not here enter into details, but
will only cite a few instances indicating the general direction of the
arguments. The phenomenon to which I refer is that so ably treated of
by Mr. A. R. Wallace (see Part I., p. 32, note 20) and others. One male
has often two or more distinctly coloured females, and in such cases
one form of the female generally resembles the male in colour. Cases
of polymorphic _mimetic_ females may for the present be excluded, in
order to reduce the argument to its greatest simplicity. Thus, in the
case of native species, _Colias Edusa_ has two females, one having the
orange ground-colour of the male, and the other the well-known light
form, var. _Helice_. So, also, _Argynnis Paphia_ has a normal female
and the dark melanic form var. _Valezina_. Numerous other cases might
be mentioned among exotic species; and, looking at the phenomenon as a
whole, it is seen to be one of _gradation_. For instance, our common
“Blues” (_Plebeius Icarus_, _P. Thetis_, &c.) have females showing a
complete gradation between the ordinary blue male and the brown female
coloration. In a large number of specimens of _Callosune Eupompe_
in my cabinet, collected in Arabia by the late J. K. Lord, there is
a completely graduated series of females, varying from individuals
having the scarlet tips of the fore-wings as strongly developed as in
the males, to specimens without a trace of such colouring; and the
same is the case with other species of this and allied genera. In
such instances it is only necessary for the intermediate female forms
to become extinct, in order to have true cases of dimorphism. It is
significant that in 1877, when _Colias Edusa_ appeared in this country
in such extraordinary profusion, large numbers of _intermediate forms_
were captured, these forming an uninterrupted series connecting the
normal female and the var. _Helice_. R.M.]
[109] [Many of our best describers of caterpillars, such as the late
Edward Newman, Messrs. Hellins and Buckler, &c., have described the
various forms of numerous polymorphic species, but not from the point
of view of the comparative morphology and ontogeny of the markings.
R.M.]
[110] [In Butler’s revision both these species are placed in the genus
_Hemaris_. R.M.]
[111] [This species is figured also by Butler (_loc. cit._ Pl. XC.,
Fig. 9), who represents it with seven oblique green lines between the
spiracles and below the subdorsal line. R.M.]
[112] “Cat. E. Ind. Co. Mus.,” Pl. VIII., Fig. 2. [Walker, Lepidop.
Heter. VIII., p. 92, No. 14, 1856; this species is strictly confined to
Java. R.M.]
[113] [Eng. ed. The caterpillar is described and figured by Millière,
“Iconographie des Chenilles et Lépidoptères inédits,” tome iii., Paris,
1869; also in the Annales, Soc. Linn. de Lyon, 1871 and 1873.] [This
sp. = _Hemaris Croatica_, Esper., of Butler’s revision. R.M.]
[114] [The following additional species of the subfamily
_Macroglossinæ_ have been figured by Butler:--_Lophura Hyas_, Walk.
(_loc. cit._ Pl. XC., Figs. 1 and 2), Hong-Kong, Silhet, and Java. The
larva is apparently figured in two stages, the younger being red-brown
with oblique white stripes, and the head and three front segments
green. The larger specimen is green, mottled with red-brown, and no
oblique stripes. In both figures the subdorsal line is indicated. The
whole colouring is very suggestive of protective resemblance. _Hemaris
Hylas_, Linn., from China, Japan, Ceylon, India, Australia, and Africa
(_loc. cit._ Pl. XC., Fig. 4). The upper part of the body is light
blue, and the lower part green, the two areas being separated by a
white subdorsal line bordered above with brown. The dorsal line is
feebly represented. _Macroglossa Belis_, Cram., N. India (_loc. cit._
Pl. XC., Fig. 6), is figured with the ground-colour deep indigo; a
conspicuous white subdorsal, and a yellow spiracular line is present;
on the side of each segment, between the two lines mentioned, there
is a large red spot with a yellow nucleus (? eye-spots), the spots
decreasing in size towards the head and tail; these probably confer
upon this species some special protective advantage. _Macroglossa
Pyrrhosticta_, Butler, China and Japan (_loc. cit._ Pl. XC., Fig.
8), is greenish-white with dorsal and subdorsal lines, and seven
dark oblique stripes along the sides, below the subdorsal line.
Of the foregoing species _Hemaris Hyas_ appears to be in the same
phyletic stage as _M. Stellatarum_ and _M. Croatica_, &c., whilst _M.
Pyrrhosticta_ is probably, together with _M. Corythus_ and _M. Gilia_,
in another and more advanced stage, which is also passed through by
_Lophura Hyas_ in the course of its ontogenetic development. This last
species (adult) and _M. Belis_ may represent phyletic stages still
further advanced. _Caliomma Pluto_, Walk., of which the caterpillar is
figured by Burmeister (_loc. cit._ Pl. XIII., Fig. 1), appears to be
a case of special protective resemblance to a twig or branch of its
food-plant. Figured also by Chavannes; Bull. Soc. Vadoise des Sci.
Nat., Dec. 6th 1854. R.M.]
[115] [Genus _Pterogon_, Boisd., = _Proserpinus_ and _Lophura_ (part).
Butler, _loc. cit._ p. 632. The species above treated of = _Proserpinus
Œnotheræ_, Fabr. R.M.]
[116] [These species = _Thyreus Abboti_ and _Proserpinus Gauræ_
of Butler’s revision. Of the former he states:--“Transformations
described, and larva and imago figured, Am. Ent. ii. p. 123, 1870; the
larva is also figured by Scudder in Harris’s ‘Correspondence,’ Pl.
III., Fig. 1 (1869), and by Packard in his ‘Guide,’ p. 276, Fig. 203.”
R.M.]
[117] [_Proserpinus (Sphinx) Gorgon_, Esp. R.M.]
[118] Rösel, _loc. cit._ vol. iii., p. 26, note.
[119] Figured and described by Abbot and Smith. [_Macrosila (Sphinx)
Cingulata_ is figured also by Burmeister, _loc. cit._ Pl. XII., Fig. 1.
R.M.]
[120] Figured in “Cat. Lep. E. Ind. Co.”
[121] See the figure in Sepp’s Surinam Lepidoptera, P. 3, Pl. CI.,
1848. A specimen in alcohol of the adult caterpillar is in the
Berlin Museum. [The following is the synonymy of the above mentioned
species:--_Macrosila Hasdrubal_, Walk. = _Pseudosphinx (Sphinx)
Tetrio_, Linn.; _M. Cingulata_ = _Protoparce (Sphinx) Cingulata_,
Fabr.; _M. Rustica_ = _Protoparce (Sphinx) Rustica_, Fabr.; _Sphinx
Convolvuli_, Linn. = _Protoparce Convolvuli_; _S. Carolina_, Linn. =
_P. Carolina_; the other species remain in the genera, as given above.
The following additional species of _Sphinginæ_ and _Acherontiinæ_
have been figured by Butler:--_Pseudosphinx Cyrtolophia_, Butl.,
from Madras (_loc. cit._ Pl. XCI., Figs. 11 and 13); _Protoparce
Orientalis_, Butl., from India, China, Java, &c. (Pl. XCI., Fig. 16);
_Diludia Vates_, Butl. from India, &c. (Pl. XCI., Fig. 18); _Nephele
Hespera_, Fabr., from India, Australia, &c. (Pl. XCI., Fig. 20);
_Acherontia Morta_, Hübn., from Java, China, India, &c. (Pl. XCII.,
Fig. 9); and _A. Medusa_, Butl., from nearly the same localities as
the last (Pl. XCII., Fig. 10). Most of these species fall under Dr.
Weismann’s general remarks, so that it is unnecessary to give detailed
descriptions. The most divergent marking is that of _P. Cyrtolophia_,
which has a broad white dorsal line bordered with pink, and two large
pink ovals on the back of the four anterior segments, the hindmost and
larger of these being bisected by the dorsal line. In _N. Hespera_ the
subdorsal line is present on segments 6 to 11 only, and it is highly
significant that the oblique stripes are absent from these segments,
but are present on the anterior segments, where the subdorsal line
fails. With reference to the larva of _A. Atropos_, Mr. Mansel Weale
states (Proc. Ent. Soc. 1878, p. v.) that in S. Africa the ordinary
form feeds generally on _Solanaceæ_, whilst the darker and rarer
variety is found only on species of _Lantana_. The following species
of these subfamilies are figured by Burmeister: _Amphonyx Jatrophæ_
(_loc. cit._ Pl. XI., Fig. 1); _Protoparce (Diludia) Florestan_, Cram.
(Fig. 2); _Sphinx Justiciæ_, Walk. (Fig. 3); _Protoparce (Diludia)
Lichenea_, Walk. (Fig. 4); _Sphinx (Protoparce) Cingulata_, Fabr. (Pl.
XII., Fig. 1); and _Sphinx Cestri_ (Fig. 5). All these species have the
characteristic Sphinx-like markings. _Dilophonota Ello_, Linn. (Pl.
XII., Fig. 2), is greenish-brown with a yellow subdorsal line, and
_D. Hippothöon_ (Fig. 4), yellow with a whitish subdorsal. Neither of
these has oblique stripes. _D. Œnotrus_, Cram. (Fig. 3), has neither
stripes nor subdorsal, but is uniform brown above, passing into green
beneath. _Protoparce Albiplaga_, Walk. (Pl. XIII., Fig. 2, also Mérian,
Pl. III., and Abbot and Smith, I., Pl. XXIV.), pale green with large
yellow, black-bordered patches surrounding the spiracles. _Pseudosphinx
Tetrio_, Linn. (Pl. XIII., Fig. 3), and _P. Scyron_ (Fig. 4) are black
with broad transverse belts, yellow and white respectively, encircling
the middle of each segment. These light bands serve very effectively to
break up the uniform surface of the large bodies of these insects, but
the whole marking is suggestive of distastefulness. R.M.]
[122] [The species referred to is placed by Butler in Hübner’s genus
_Hyloicus_. R.M.]
[123] [= _Ellema Coniferarum_, of Butler’s revision. R.M.]
[124] [= _Dilophonota Ello_ of Butler’s revision. R.M.]
[125] “Synopsis of the North American Sphingides.” Philadelphia, 1859.
[126] [The larvæ of many moths which feed on deciduous trees during
the autumn and hibernate, are stated to feed on low-growing plants in
the spring, before the buds of their food-trees open. On the other
hand, low-plant feeders, such as _Triphæna Fimbria_, &c., are stated
to sometimes feed at night in early spring on the buds of trees.
The habits and ontogeny of these species are of special interest
in connection with the present researches, and are well worthy of
investigation. R.M.]
[127] “Neuer Beitrag zum geologischen Beweise der Darwin’schen
Theorie.” 1873, Nos. 1 and 2. [This principle, in common with many
others which have only been completely worked out of late years, is
foreshadowed by Darwin. Thus, he states when speaking of inheritance
at corresponding periods of life: “I could give a good many cases
of variations (taking the word in the largest sense) which have
supervened at an earlier age in the child than in the parent” (“Origin
of Species,” 1st ed., 1860, p. 444). In the case of inherited diseases
also: “It is impossible to ... doubt that there is a strong tendency to
inheritance in disease at corresponding periods of life. When the rule
fails, the disease is apt to come on earlier in the child than in the
parent; the exceptions in the other direction being very much rarer.”
(“Variation of Animals and Plants under Domestication,” 1st ed., 1868,
vol. ii., p. 83.) R.M.]
[128] [If the reddish-brown spots on the larva of _S. Populi_ have
the protective function assigned to them by Mr. Peter Cameron (Trans.
Ent. Soc. 1880, p. 69), it can be readily understood that they would
be of service to the insect in the fourth stage, and the backward
transference of this character might thus be accelerated by natural
selection, in accordance with the above principles. (See, also,
note 100, p. 241.) R.M.]
[129] [For cases of correlation of habit with protective resemblance
in larvæ, see a paper in “Ann. and Mag. of Nat. Hist.,” Feb., 1878,
pp. 159, 160. Also Fritz Müller on a Brazilian Cochliopod larva,
Trans. Ent. Soc. 1878, p. 223. Mr. Mansel Weale states, with reference
to S. African _Sphingidæ_ (Proc. Ent. Soc. 1878, p. vi.), that many
species when seized “have a habit of doubling up the body, and then
jumping a considerable distance with a spring-like action. This is
especially the case with species having eye-like markings; and it
is probable that if attacked by birds in a hesitating manner, such
species might effect their escape amid the grass or foliage.” Many
of the defensive weapons and habits of larvæ are doubtless means of
protection from ichneumons and other parasitic foes. In the case of
saw-flies, Mr. Peter Cameron has shown (Trans. Ent. Soc. 1878, p. 196)
that the lashing about of the posterior part of the body may actually
frighten away such enemies. The grotesque attitude and spider-like
appearance and movements of the caterpillar of _Stauropus Fagi_ are
considered by Hermann Müller (“Kosmos,” Nov., 1879, p. 123) to be means
of protection from ichneumons. Among the most remarkable means of
defence possessed by larvæ is that of secreting a liquid, which Mr. W.
H. Edwards has shown, in the case of certain North American _Lycænidæ_
(“Canadian Entomologist.” vol. x., 1878, pp. 3-9 and 131-136), to be
attractive to ants, who regularly attend these caterpillars, in the
same manner and for the same purpose as they do our aphides. The mutual
advantage derived by the ants and larvæ was discovered in the case of
_Lycæna Pseudargiolus_. Mr. Edwards states that the _mature_ larva
of this species is singularly free from Hymenopterous and Dipterous
parasites:--“Why this species, and doubtless many other _Lycænæ_,
are thus favoured will, perhaps, in some degree appear from a little
incident to be related. On 20th June, in the woods, I saw a mature
larva on its food-plant; and on its back, facing towards the tail of
the larva, stood motionless one of the larger ants.... At less than
two inches behind the larva, on the stem, was a large ichneumon-fly,
watching its chance to thrust its ovipositor into the larva. I bent
down the stem, and held it horizontally before me, without alarming
either of the parties. The fly crawled a little nearer and rested,
and again nearer, the ant making no sign. At length, after several
advances, the fly turned its abdomen under and forward, thrust out
its ovipositor, and strained itself to the utmost to reach its prey.
The sting was just about to touch the extreme end of the larva, when
the ant made a dash at the fly, which flew away, and so long as I
watched--at least five minutes--did not return. The larva had been
quiet all this time, its tubes out of sight, and head buried in a
flower-bud, but the moment the ant rushed and the fly fled, it seemed
to become aware of the danger, and thrashed about the end of its body
repeatedly in great alarm. But the tubes were not protruded, as I was
clearly able to see with my lens. The ant saved the larva, and it is
probable that ichneumons would in no case get an opportunity to sting
so long as such vigilant guards were about. It strikes me that the
larvæ know their protectors, and are able and willing to reward them.
The advantage is mutual, and the association is friendly always.” Those
who are familiar with Mr. Belt’s description of the standing armies of
ants kept by the “bull’s-horn thorn” (“Naturalist in Nicaragua,” pp.
218-222) and by certain _Cecropiæ_ and _Melastomæ_, will be struck with
the analogy between these and the foregoing case. R.M.]
[130] [The adaptive resemblance is considerably enhanced in _Catocala_
and in _Lasiocampa Quercifolia_ by the row of fleshy protuberances
along the sides of these caterpillars, which enables them to rest
on the tree trunks by day without casting a sharp shadow. The hairs
along the sides of the caterpillar of _Pæcilocampa Populi_ doubtless
serve the same purpose. (See a paper by Sir John Lubbock, Trans. Ent.
Soc. 1878, p. 242; also Peter Cameron, _ibid._, 1880, p. 75.) It is
well known to collectors that one of the best methods of finding the
caterpillars of the _Catocalæ_ is to _feel_ for them by day on the
barks of their respective food-trees, or to beat for them at night.
R.M.]
[131] [See Wallace’s “Contributions to the Theory of Natural
Selection,” 1st ed., p. 62. Also a paper in “Ann. Mag. Nat. Hist.” Feb.
1878, p. 159, for cases in point. Rösel in 1746 mentioned this habit
in _Calocampa Exoleta_. Hermann Müller has recorded many other similar
instances on the authority of Dr. Speyer; see “Kosmos,” Nov., 1879, p.
114. R.M.]
[132] [Andrew Murray called attention to this fact in 1859 (“Edinburgh
New Philos. Journ.,” Jan., 1860, p. 9). This view is also corroborated
by the fact that no internal feeders are green; see note 142, p. 310
and Proc. Zoo. Soc. 1873, p. 159. R.M.]
[133] [Proc. Ent. Soc. March 4th, 1867; and “Contributions to the
Theory of Natural Selection,” 1st ed., pp. 117-122; also Darwin’s
“Descent of Man,” 2nd ed., p. 325. Among the most important recent
additions to the subject of the colours, spines, and odours of
caterpillars, I may call attention to a paper by Fritz Müller
(“Kosmos,” Dec., 1877), the following abstract of which I communicated
to the Entomological Society (Proc. 1878, pp. vi, vii):--“The larvæ of
_Dione Juno_ and _Acræa Thalia_ live gregariously, and are brown in
colour; they are covered with spines, but, being of dull colours, their
spiny protection (which in the case of _D. Juno_ is very imperfect)
would not preserve them unless they were distinguished as inedible at
the right time, and not after being seized, in accordance with the
principles laid down by Mr. Wallace. It is suggested that the social
habits of the larvæ which lead then to congregate in large numbers,
make up for their want of colour, since their offensive odour then
gives timely warning to an approaching enemy. The caterpillars of
_Colænis Julia_ and _Dione Vanillæ_ are equally wanting in bright
colours, but are solitary in their habits, and these species rest
on the under side of the leaf when feeding. On the other hand,
the caterpillars of _Heliconius Eucrate_, _Colænis Dido_, and _C.
Isabella_, which are of solitary habits, and which freely expose
themselves, are very gaudily coloured, and therefore most conspicuous.
As examples of nearly allied larvæ, of which some species are
gregarious and others solitary, Fritz Müller mentions _Morpho_ and
_Brassolis_, which are gregarious; while _Opsiphanes_ and _Caligo_
are solitary. The larva of _Papilio Pompeius_ also is gregarious,
and those of _P. Nephalion_, _P. Polydamas_, and _P. Thoas_ are
solitary.... Fritz Müller sums up his observations by remarking that
those caterpillars which live alone, and lack the bright colouring as
a sign of offensiveness, must hide themselves; as those of _C. Julia_
and _D. Vanillæ_. The spiny covering is much less a protection against
birds than against smaller enemies; and they may, by the protective
habit of living together, diffuse around themselves an offensive
atmosphere, even to man, and thus gradually becoming shorter (as with
_D. Juno_), the spines of these caterpillars become useless, and
finally are altogether dropped.” See also Sir John Lubbock’s “Note on
the Colours of British Caterpillars,” Trans. Ent. Soc. 1878, p. 239.
Mr. Peter Cameron finds (Trans. Ent. Soc. 1880, pp. 71 and 75) that
these remarks are also applicable to the larvæ of certain saw-flies. In
1877 Mr. J. W. Slater published a paper “On the Food of gaily-coloured
Caterpillars” (Trans. Ent. Soc. 1877, p. 205), in which he suggested
that such caterpillars might derive their distasteful qualities from
feeding on plants containing poisonous or otherwise noxious principles.
A much larger number of observations will be required, however, before
this view can be accepted as of general application. A beautiful
illustration of the theory of warning colours is given by Belt in his
“Naturalist in Nicaragua,” p. 321. All the frogs found in the woods
round St. Domingo are, with one exception, protectively coloured; they
are of nocturnal habits, and are devoured by snakes and birds. The
exception was a species of bright red and blue colours, which hopped
about by day and made no attempt at concealment. From these facts
Mr. Belt concluded that this species was inedible, and on trying the
experiment with ducks and fowls this was found to be the case. R.M.]
[134] See the essay “Über den Einfluss der Isolirung auf die
Artbilding.” Leipzig, 1872, p. 22.
[135] [See also preceding note 133, p. 294. R.M.]
[136] [Eng. ed. The habit of hiding by day occurs also in those
caterpillars which resemble the bark of their food-trees. Thus
_Catocala Sponsa_ and _Promissa_ conceal themselves by day in crevices
of the bark, and are, under these circumstances, only found with
difficulty. Dr. Fritz Müller also writes to me that in Brazil the
caterpillars of _Papilio Evander_ rest in this manner in large numbers,
crowded together into dense masses, on the trunks of the orange-trees,
which they resemble in colour.]
[137] “Über den Einfluss der Isolirung auf die Artbildung.” Leipzig,
1872, p. 21.
[138] I am unfortunately not able to give exact numbers showing the
relative proportions of the different forms, since I have never bred
_S. Convolvuli_ from eggs, nor _C. Elpenor_ in sufficient numbers.
[139] [With reference to _C. Porcellus_, see note 71, p. 188. R.M.]
[140] [In the class of cases treated of in the foregoing portions
of this essay, the external conditions remain unaltered during the
lifetime of the caterpillar, but change of habit, and in some cases
of colour, occurs when the insect has attained a size conceivable _à
priori_, and are realized by observation, in which the environment
itself may undergo change during the lifetime of the individual
caterpillar. Thus, in the case of hibernating species, the colour which
is adaptive to the autumnal colours of the foliage of their food-trees
would not assimilate to that of the newly-opened leaves in the spring.
I have already quoted (Proc. Zoo. Soc. 1873, p. 155) as instances
of what may be called “seasonal adaptation,” the larvæ of _Geometra
Papilionaria_, _Acidalia Degenararia_, and _Gnophos Obscurata_, and
many more could be named. These species undergo a change of colour
before or after hibernation, the change being always adaptive to the
environment.
It has long been known that caterpillars which feed on flowers or on
plants of variously-coloured foliage, in some cases partake of the
colour of their food. See, for instance, Dr. L. Möller’s memoir, “Die
Abhängigkeit der Inseckten von ihrer Umgebung,” 1867, and B. D. Walsh
“On Phytophagic Varieties and Phytophagic Species,” Proc. Ent. Soc.
Philadelph., vol. iii., p. 403. In 1865 Mr. R. McLachlan published a
paper entitled “Observations on some remarkable varieties of _Sterrha
Sacraria_, Linn., with general notes on variation in Lepidoptera”
(Trans. Ent. Soc. 1865, p. 453), in which he gave many illustrations
of this phenomenon. The larva of _Heliothis Peltiger_, according to
Mr. Reading’s description (Newman’s “British Moths,” p. 438), is
another case in point. In 1874 a number of instances were published
by Mr. Thomas G. Gentry in a paper entitled “Remarkable Variations in
Coloration, Ornamentation, &c., of certain Crepuscular and Nocturnal
Lepidopterous Larvæ” (“Canadian Entomologist,” vol. vi., p. 85. See
also W. H. Edwards’ description of the summer and autumnal larvæ of
_Lycæna Pseudargiolus_; _Ibid._, vol. x., pp. 12, 13).
The caterpillars of the _Sphingidæ_ appear also in some cases to vary
in a manner very suggestive of phytophagic influences. The observations
upon _S. Ocellatus_ recorded in the previous note (p. 241) may perhaps
be interpreted in this sense. In order to get experimental evidence
upon this subject, I may add that Mr. E. Boscher was good enough at
my request to repeat his observations, and conduct some breeding
experiments during the present year (1880). In the same locality as
that previously mentioned, seven larvæ were found feeding on _Salix
viminalis_, all of which were the bright green spotted variety; and
in the same osier-bed six more were found on another species of
_Salix_, two of these being the bluish-green variety, and the other
four the bright green form. Unless we have here a local race, these
observations, in connection with those of last year, tend to show
that the light green form is associated with _Salix viminalis_. When
found in the natural state feeding on apple, the caterpillar of this
species is generally, perhaps invariably, the bluish-green form. In
order to try the effect of breeding the larvæ _ab ovo_ on distinct
food-plants, a large number of eggs laid by a female _Ocellatus_ in
July were divided into three batches, one being supplied with _Salix
triandra_, another with _S. viminalis_, and the third lot with apple.
The experiment unfortunately failed in great part, owing to most of the
larvæ dying off, three from the third lot only surviving; but these
were all of the bluish-green form, which colour was shown by all the
caterpillars of this batch from their earliest stage. The observation
is thus so far successful, as it goes to support the view that the
variety mentioned is associated with apple (and _S. triandra?_) My
friend Mr. W. J. Argent informs me that he had a number of specimens
of _Sphinx Ligustri_ in his possession this autumn, some of which had
been found on lilac and others on laurestinus, and he states that all
those on the latter plant had the ground-colour distinctly darker than
in those feeding on lilac. I learn also from Mr. W. Davis, of Dartford,
that he found a number of these larvæ this year feeding on ash, and
that they were all differently coloured to those found on lilac or
privet, being of a more greyish-green. Another case of colour-variation
in larvæ is that _Emmelesia Unifasciata_, specimens of which I have
recently had an opportunity of examining, through the courtesy of Mr.
W. Davis. This species feeds on the seeds of a species of _Bartsia_
when the capsules are in various stages of growth, and (omitting
details of marking) those caterpillars found on the green capsules
were green, whilst those on the brown capsules were of a corresponding
colour.
On the whole I am inclined to believe that sufficient importance
has not hitherto been given to phytophagic variability as a
factor in determining larval coloration, and a large field for
experimental investigation here lies open for future work. The
obscure chemico-physiological processes which may perhaps be shown
by such researches to lead to phytophagic variation, cannot, I am
persuaded, produce any great divergence of character if unaided;
but when such causes of variability play into the hands of natural
selection variations of direct _protective advantage_ to the species,
we can easily see that this all-important agency would seize upon and
perpetuate such a power of adaptability to a variable environment. (See
Proc. Zoo. Soc. 1873, p. 158, and “Nature,” vol. xiv., pp. 329 and
330.) R.M.]
[141] [In 1879 Mr. George Francis, of Adelaide, forwarded from the
latter place a number of moths (a species of Anapæa) together with
their larvæ (in alcohol) and cocoons (Proc. Ent. Soc. 1879, p. xvi),
and in an accompanying note he stated that the male larva when living
is of “a bright emerald green, with red and pink markings on the back,
and yellow, black, and white streaks on the sides.” The male larva
is described as being smaller than the female, and as possessing
all the brilliant colours, the latter “having no red markings, but
only white, yellow, and green, with a little black.” I was at first
disposed to think that we might be dealing here with two distinct
species having differently marked larvæ; but Mr. Francis this present
year (1880) forwarded a large number of the living cocoons of this
species, which I separated according to size, and, on the emergence
of the moths (August), I found that all those from the small cocoons
were males, and those from the larger cocoons females. There can be no
doubt, therefore, that we have but one species in this case, the larva
of which presents the remarkable phenomenon of sexual difference of
coloration. As an analogous fact I may here mention the well-known case
of _Orgyia Antiqua_, the larva of which differs in the colour of the
tufts of hair according to sex. R.M.]
[142] [I have already given reasons for suspecting that the colour of
green caterpillars may be due to the presence of chlorophyll (or some
derivative thereof) in their tissues (see Proc. Zoo. Soc. 1873, p.
159). This substance appears to be one of great chemical stability,
and, according to Chautard, who has detected it in an unaltered
state in the tissues of certain leaf-feeding insects by means of its
absorption spectrum (“Comp. Rend.” Jan. 13th, 1873), it resists the
animal digestive processes (Ann. Ch. Phys. [5], iii., 1-56). If this
view should be established by future observations, we must regard the
green colour of caterpillars as having been produced, when protective,
from phytophagic variability by the action of natural selection; and
the absence of colour in internal feeders, above referred to, is only
secondarily due to the exclusion of light, and depends primarily on
the absence of chlorophyll in their food. In connection with this
I may adduce the fact, that some few species of _Nepticula_ (_N.
Oxyacanthella_, _N. Viscerella_, &c.) are green, although they live in
leaf-galleries where this colour can hardly be of use as a protection;
but their food (hawthorn and elm) contains chlorophyll. See also note
130, p. 293. Further investigations in this direction are much needed.
R.M.]
[143] [The same applies to _Pseudoterpna Cytisaria_, also feeding on
broom at the same time of the year. The most striking cases of adaptive
resemblance brought about by longitudinal stripes are to be found among
fir and pine feeders, species belonging to the most diverse families
(_Hyloicus Pinastri_, _Trachea Piniperda_, _Fidonia Piniaria_, &c.,
&c.) all being most admirably concealed among the needle-shaped leaves.
R.M.]
[144] The geographical distribution of the dark form indicates that
in the case of this species also, the form referred to is replacing
the yellow (green) variety. Whilst in the middle of Europe (Germany,
France, Hungary) the dark form is extremely rare, in the south of
Spain this variety, as I learn from Dr. Noll, is almost as common as
the yellow one. I hear also from Dr. Staudinger that in South Africa
(Port Natal) the dark form is somewhat the commoner, although the
golden-yellow and, more rarely, the green varieties, occur there. I
have seen a caterpillar and several moths from Port Natal, and these
all agree exactly with ours. The displacement of the green (yellow)
form by the dark soil-adapted variety, appears therefore to proceed
more rapidly in a warm than in a temperate climate. [Eng. ed. Dr.
Noll writes to me from Frankfort that the caterpillar of _Acherontia
Atropos_ in the south of Spain does not, as with us, conceal itself by
day in the earth, but on the stems underneath the leaves. “At Cadiz, on
the hot, sandy shore, _Solanum violaceum_ grows to a height of three
feet, and on a single plant I often found more than a dozen _Atropos_
larvæ resting with the head retracted. It can easily be understood
why the lateral stripes are blue when one has seen the south European
_Solaneæ_, on which this larva is at home. _Solanum violaceum_ is
scarcely green: violet tints alternate with brown, green, and yellow
over the whole plant, and between these appear the yellow-anthered
flowers, and golden-yellow berries of the size of a greengage. Thus
it happens that the numerous thorns, an inch long, between which the
caterpillar rests on the stem, pass from violet into shades of blue,
red, green, and yellow.”]
[145] [For Mr. J. P. Mansel Weale’s remarks on the habits of certain
ocellated S. African Sphinx-larvæ see note 129, p. 290. R.M.]
[146] [Some experiments with the caterpillar of _C. Elpenor_,
confirming these results, have been made by Lady Verney. See “Good
Words,” Dec. 1877, p. 838. R.M.]
[147] [The eye-spots on _Ch. Nerii_ have thus been supposed by some
observers to be imitations of the flowers of the periwinkle, one of
its food-plants. See, for instance, Sir John Lubbock’s “Scientific
Lectures,” p. 51. R.M.]
[148] “On Insects and Insectivorous Birds,” Trans. Ent. Soc. 1869, p.
21.
[149] _Ibid._, p. 27.
[150] [Messrs. Weir and Butler inform me that they have not
experimented with Sphinx-larvæ. R.M.]
[151] [It appears that the nauseous character of these last butterflies
is to a certain extent retained after death, as I found that in an
old collection which had been destroyed by mites, the least mutilated
specimens were species of _Danais_ and _Euplæa_, genera which are known
to be distasteful when living, and to serve as models for mimicry. See
Proc. Ent. Soc. 1877, p. xii. R.M.]
[152] [This bears out the view expressed in a previous note 129, p.
290, that the grotesque attitude and caudal tentacles are more for
protection against ichneumons than against larger foes. R.M.]
[153] These experiments, as already mentioned above, were not made with
the common German lizard (_Lacerta Stirpium_), but with the large South
European _Lacerta Viridis_.
[154] Thus, Boisduval states of this caterpillar, which in Provence
lives on _Euphorbia esula_ and allied species:--“Its resemblance
to a serpent, and its brilliant colour, permit of its being easily
discovered.” This was written in 1843, long before natural selection
was thought of.
[155] Or some other extinct analogously-marked species.
[156] [See Darwin’s remarks on the struggle for life being most severe
between individuals and varieties of the same species “Origin of
Species,” 6th ed. p. 59. R.M.]
[157] [Compare this with Darwin’s remarks on “analogous variations,”
“Origin of Species,” 6th ed., p. 125. R.M.]
[158] “Zoologische Studien auf Capri. II. Lacerta muralis cærula,
ein Beitrag zur Darwin’schen Lehre.” Leipzig, 1874. [The subject of
colour-variation in lizards has been much discussed in “Nature” since
the publication of the above mentioned essay; see vol. xix., pp. 4, 53,
97, and 122, and vol. xx., pp. 290 and 480. R M.]
[159] “Über die Berechtigung der Darwin’schen Theorie.” Leipzig,
1868. See also the previous essay “On the Seasonal Dimorphism of
Butterflies,” pp. 112-116.
[160] [Mr. A. G. Butler has recently advanced the view that this family
is not allied to the _Sphingidæ_, but is related on the one side to the
_Pyrales_, and on the other to the _Gelechiidæ_. See his paper “On the
Natural Affinities of the Lepidopterous Family _Ægeriidæ_,” Trans. Ent.
Soc. 1878, p. 121. R.M.]
[161] I am indebted to my esteemed colleague, Prof. Gestäcker, for the
knowledge of this specimen.
[162] Cat. Lep. East India Co., Pl. VIII.
[163] Such a residue is distinctly visible in _S. Ocellatus_: see Fig.
70, Pl. VII.
[164] [The question here also suggests itself as to why the _dorsal_
line should not have been the primary longitudinal stripe, seeing
that such a marking is almost naturally produced in many caterpillars
by the food in the alimentary canal; or, in other words, why has not
natural selection taken advantage of such an obvious means of producing
a stripe in cases where it would have been advantageous? In answer
to this I may state, that in large numbers of species the dorsal
line has thus become utilized; but in the case of large caterpillars
resting among foliage, it can be easily seen that light lateral (_i.e._
subdorsal) stripes, are more effective in breaking the homogeneity
of the body than a dorsal line only slightly darker than the general
ground-colour. Lateral lines are in fact visible from _two directions
of space_. If a caterpillar thus marked be placed on a twig, these
lines are visible when we look at the creature’s back or at either
side. That the subdorsal are therefore the primary lines, as shown by
Dr. Weismann’s observations of the ontogeny of many of the _Sphingidæ_,
is quite in harmony with the view of their having been produced by
natural selection. R.M.]
[165] “Die Darwin’sche Theorie. Elf Vorlesungen über die Entstehung der
Thiere und Pflanzen durch Naturzüchtung.” 2nd ed., Leipzig, 1875, p.
195.
[166] [In the following species, already mentioned in previous
notes, the oblique stripes are bounded at their upper extremities by
a conspicuous subdorsal line:--_Acosmeryx Anceus_, Cram.; _Sphinx
Cingulata_, Fabr.; _Pachylia Ficus_, Linn.; _P. Syces_, Hübn. In
_Pseudosphinx Cyrtolophia_, Butl., the oblique white stripes,
beautifully shaded with pink, run into the white pink-bordered dorsal
line, so that when seen from above the markings present the appearance
of the midrib and lateral veins of a leaf, and are probably specially
adapted for this purpose. R.M.]
[167] [The dorsal line as well as the oblique stripes is present in
the caterpillar of _Smerinthus Tartarinovii_, Ménét.; and in _Ambulyx
Gannascus_, Stoll., the oblique stripes are bounded above by a
subdorsal line, as in the species named in the preceding note. R.M.]
[168] Cat. Lep. East India Co., Pl. XI.
[169] [Compare this with Darwin’s “Origin of Species” (1st. ed. p.
440), where it is stated that when an animal, during any part of its
embryonic career, is active, and has to provide for itself, “the
period of activity may come on earlier or later in life; but whenever
it comes on, the adaptation of the larva to its conditions of life is
just as perfect and beautiful as in the adult animal. From such special
adaptations the similarity of the larvæ or active embryos of allied
animals is sometimes much obscured.” R.M.]
[170] [For Fritz Müller’s application of this principle to the case of
certain groups of Brazilian butterflies see Appendix II. to this Part.
R.M.]