THE NATURAL HISTORY OF THE COCKROACH.
_SPECIAL REFERENCES._
HUMMEL. Essais Entomologiques, No. 1 (1821).
CORNELIUS. Beiträge zur nähern Kenntniss von Periplaneta orientalis
(1853.)
GIRARD. La domestication des Blattes. Bull. Soc. d’Acclimatisation,
3^e Sér., Tom. IV., p. 296 (1877).
_Range._
The common Cockroach is native to tropical Asia,[14] and long ago made
its way by the old trade-routes to the Mediterranean countries. At the
end of the sixteenth century it appears to have got access to England
and Holland, and has gradually spread thence to every part of the world.
[14] Linnæus was certainly mistaken in his remark (Syst. Nat., 12th
ed.) that this species is native to America, and introduced to the
East--“Habitat in America: hospitatur in Oriente.” He adds, “Hodie in
Russiæ adjacentibus regionibus frequens; incepit nuperis temporibus
Holmiæ, 1739, uti dudum in Finlandia.”
Perhaps the first mention of this insect in zoological literature
occurs in Moufet’s Insectorum Theatrum (1634), where he speaks of the
Blattæ as occurring in wine cellars, flour mills, &c., in England. It
is hard to determine in all cases of what insects he is speaking, since
one of his rude woodcuts of a “Blatta” is plainly _Blaps mortisaga_;
another is, however, recognisable as the female of _P. orientalis_; a
third, more doubtfully, as the male of the same species. He tells how
Sir Francis Drake took the ship “Philip,”[15] laden with spices, and
found a great multitude of winged Blattæ on board, “which were a little
larger, softer, and darker than ours.” Perhaps these belonged to the
American species, but the description is obscure. Swammerdam also was
acquainted with our Cockroach as an inhabitant of Holland early in the
seventeenth century. He speaks of it as “insectum illud Indicum, sub
nomine Kakkerlak satis notum,” and very properly distinguishes from
it “the species of Scarabæus” (_Blaps_), which Moufet had taken for a
Blatta.[16]
[15] This must have been the “San Felipe,” a Spanish East Indiaman,
taken in 1587. See Motley, United Netherlands, Vol. II., p. 283.
[16] Biblia Naturæ, Vol. I., p. 216.
The American Cockroach is native to tropical America, but has
now become widely spread by commerce. An Australian species also
(_P. australasiæ_) has begun to extend its native limits, having
been observed in Sweden,[17] Belgium, Madeira, the East and West
Indies,[18] Florida,[19] &c. In Florida it is said to be the torment of
housekeepers.
[17] De Borck. Skandinaviens rätvingade Insekters Nat. Hist., I.,
i., 35.
[18] Brunner. N. Syst. d. Blattaires, p. 234.
[19] Scudder. Proc. Boston Soc. N.H., Vol. XIX., p. 94.
To the genus _Blatta_ belong a number of small European species, which
mostly lurk in woods and thickets. Some of these are found in the south
of England. _B. lapponica_ is one of the commonest and most widely
distributed. It is smaller than the common Cockroach, and both sexes
have long wings and wing-cases. The males are black and the females
yellow. It is found on the mountains of Norway and Switzerland as high
as shrubs extend, and when sheltered by human dwellings, can endure
the extreme cold of the most northern parts of Europe. This is the
insect of which Linnæus tells, that in company with _Silpha lapponica_
it has been known to devour in one day the whole stock of dried but
unsalted fish of a Lapland village. _B. germanica_ also has the wings
and wing-cases well developed in both sexes. Two longitudinal stripes
on the pronotum, or first dorsal plate of the thorax, are the readiest
mark of this species, which is smaller and lighter in colour than the
common Cockroach. It is plentiful in most German towns, and has been
introduced from Germany into many other countries;[20] but it appears
to be native, not to Germany alone, but to Asia and all parts of
central and southern Europe. Where and how it first became domesticated
we do not know.
[20] For example, the Russians often call it _Proussaki_, the
Prussian Cockroach, and believe that their troops brought it home
with them after the Seven Years’ War. The native Russian name
is _Tarakan_. In Finland and Sweden the same species is called
_Torraka_, which appears to be a corruption of the Russian word, and
confirms the account of Linnæus quoted above.
_B. germanica_ is found in the United States from the Atlantic to the
Pacific. It is generally known as the Croton Bug, because in New York
it is often met with about the water pipes, which are supplied from
the Croton River (Dr. Scudder).
The other species of Cockroaches which have been met with in Europe are
_Panchlora maderæ_, said by Stephens to be occasionally seen in London,
and _Blabera gigantea_ the Drummer of the West Indies, which has often
been found alive in ships in the London Docks.
_Blatta germanica_, _Periplaneta orientalis_, and _P. americana_, are
so similar in habits and mode of life as to be interchangeable, and
each is known to maintain itself in particular houses or towns within
the territory of another species, though usually without spreading.
_Orientalis_ is, for example, the common Cockroach of England, but
_germanica_ frequently gets a settlement and remains long in the same
quarters. H. C. R., in Science-Gossip for 1868, p. 15, speaks of it as
swarming in an hotel near Covent Garden, where it can be traced back as
far as 1857. In Leeds, one baker’s shop is infested by this species; it
is believed to have been brought by soldiers to the barracks, after the
Crimean war, and to have been carried to the baker’s in bread-baskets.
We have met with no instance in which it has continued to gain ground
at the expense of _orientalis_. _Americana_ also seems well established
in particular houses or districts in England. H. C. R. (loc. cit.)
mentions warehouses near the Thames, Red Lion and Bloomsbury Squares,
and the Zoological Gardens, Regent’s Park. It frequents one single
warehouse in Bradford, and is similarly local in other towns with
foreign trade.
Many cases are recorded in which _germanica_ has been replaced by
_orientalis_, as in parts of Russia and Western Germany, but detailed
and authenticated accounts are still desired. On the whole _orientalis_
seems to be dominant over both _germanica_ and _americana_.
The slow spread of the Cockroaches in Europe is noteworthy, not as
exceptional among invading species, but as one more illustration of
the length of time requisite for changes of the equilibrium of nature.
It took two centuries from the first introduction of _orientalis_ into
England for it to spread far from London. Gilbert White, writing, as
it would appear, at some date before 1790, speaks of the appearance of
“an unusual insect,” which proved to be the Cockroach, at Selborne,
and says: “How long they have abounded in England I cannot say; but
have never observed them in my house till lately.”[21] It is probable
that many English villages are still clear of the pest. The House
Cricket, which the Cockroaches seem destined to supplant, still dwells
in our houses, often side by side with its rival, sharing the same
warm crannies, and the same food. The other imported species, though
there is reason to suppose that they cannot permanently withstand
_orientalis_, are by no means beaten out of the field; they retreat
slowly where they retreat at all, and display inferiority chiefly in
this, that in countries where both are found, they do not spread, while
their competitor does. It may yet require some centuries to settle the
petty wars of the Cockroaches.
[21] Bell’s Edition, Vol. I., p. 454.
It is also worth notice that in this, as in most other cases, the
causes of such dominance over the rest as one species enjoys are
very hard to discover. We cannot explain what peculiarities enable
Cockroaches to invade ground thoroughly occupied by the House Cricket,
an insect of quite similar mode of life: and it is equally hard to
account for the superiority of _orientalis_ over the other species. It
is neither the largest nor the smallest; it is not perceptibly more
prolific, or more voracious, or fonder of warmth, or swifter than
its rivals, nor is it easy to see how the one conspicuous structural
difference--viz., the rudimentary state of the wings of the female, can
greatly favour _orientalis_. Some slight advantage seems to lie in
characteristics too subtle for our detection or comprehension.
_Food and Habits._
As to the food of Cockroaches, we can hardly except any animal or
vegetable substance from the long list of their depredations. Bark,
leaves, the pith of living cycads, paper, woollen clothes, sugar,
cheese, bread, blacking, oil, lemons, ink, flesh, fish, leather, the
dead bodies of other Cockroaches, their own cast skins and empty
egg-capsules, all are greedily consumed. Cucumber, too, they will eat,
though it disagrees with them horribly.
In the matter of temperature they are less easy to please. They
are extremely fond of warmth, lurking in nooks near the oven, and
abounding in bakehouses, distilleries, and all kinds of factories which
provide a steady heat together with a supply of something eatable. Cold
is the only check, and an unwarmed room during an English winter is
more than they can endure. They are strictly nocturnal, and shun the
light, although when long unmolested they become bolder. The flattened
body enables the Cockroach to creep into very narrow crevices, and
during cold weather it takes refuge beneath the flags of a kitchen
floor, or in other very confined spaces.
The Cockroach belongs to a miscellaneous group of animals, which may be
described as in various degrees parasitic upon men. These are all in a
vague sense domestic species, but have not, like the ox, sheep, goat,
or pig, been forcibly reduced to servitude; they have rather attached
themselves to man in various degrees of intimacy. The dog has slowly
won his place as our companion; the cat is tolerated and even caressed,
but her attachment is to the dwelling and not to us; the jackal and
rat are scavengers and thieves; the weasel, jackdaw, and magpie are
wild species which show a slight preference for the neighbourhood of
man. All of these, except the cat, which holds a very peculiar place,
possess in a considerable degree qualities which bring success in the
great competitive examination. They are not eminently specialised,
their diet is mixed, their range as natural species is wide. Apart from
man, they would have become numerous and strong, but those qualities
which fit them so well to shift for themselves, have had full play
in the dwellings of a wealthy and careless host. Of these domestic
parasites at least two are insects, the House-fly and the Cockroach;
and the Cockroach in particular is eminent in its peculiar sphere
of activity. The successful competition of Cockroaches with other
insects under natural conditions is sufficiently proved by the fact
that about nine hundred species have already been described,[22] while
their rapid multiplication and almost worldwide dissemination in the
dwellings of man is an equally striking proof of their versatility and
readiness to adapt themselves to artificial circumstances. In numerical
frequency they probably exceed all domestic animals of larger size,
while in geographical range the five species, _lapponica_, _germanica_,
_orientalis_, _americana_, and _australasiæ_, are together comparable
to the dog or pig, which have been multiplied and transported by man
for his own purposes, and which cover the habitable globe.
[22] British Museum Catalogue of Blattariæ (1868) and Supplement
(1869). It is probable that the number is over-estimated in this
catalogue, the same species being occasionally renamed.
_The Cockroach a persistent type._
The Cockroach is historically one of the most ancient, and structurally
one of the most primitive, of our surviving insects. Its immense
antiquity is shown by the fact that so many Cockroaches have been found
in the Coal Measures, where about eighty species have been met with.
The absence of well-defined stages of growth, such as the soft-bodied
larva or inactive pupa, the little specialised wings and jaws, the
simple structure of the thorax, the jointed appendages carried on the
end of the abdomen, and the unconcentrated nervous system, are marks
of the most primitive insect-types. The order Orthoptera is undeniably
the least specialised among winged insects at least, and within this
order none are more simple in structure, or reach farther back in the
geological record than the Cockroaches. The wingless Thysanura are even
more generalised, but their geological history is illegible.[23]
[23] Brongniart has just described a Carboniferous Insect which he
considers a Thysanuran (_Dasyleptus Lucasi_), though it has but one
anal appendage. See C. R. Soc. Ent., France, 1885.
_Life-History._
The eggs of the Cockroach are laid sixteen together in a large
horny capsule. This capsule is oval, with roundish ends, and has a
longitudinal serrated ridge, which is uppermost while in position
within the body of the female. The capsule is formed by the secretion
of a “colleterial” gland, poured out upon the inner surface of a
chamber (vulva) into which the oviducts lead. The secretion is at first
fluid and white, but hardens and turns brown on exposure to the air. In
this way a sort of mould of the vulva is formed, which is hollow, and
opens forwards towards the outlet of the common oviduct. Eggs are now
passed one by one into the capsule; and as it becomes full, its length
is gradually increased by fresh additions, while the first-formed
portion begins to protrude from the body of the female. When sixteen
eggs have descended, the capsule is closed in front, and after an
interval of seven or eight days, is dropped in a warm and sheltered
crevice. In _Periplaneta orientalis_ it measures about ·45 in. by
·25 in. (fig. 5). The ova develop within the capsule, and when ready
to escape are of elongate-oval shape, resembling mummies in their
wrappings. Eight embryos in one row face eight others on the opposite
side, being alternated for close packing. Their ventral surfaces,
which are afterwards turned towards the ground, are opposed, and their
rounded dorsal surfaces are turned towards the wall of capsule; their
heads are all directed towards the serrated edge. The ripe embryos
are said by Westwood to discharge a fluid (saliva?) which softens the
cement along the dorsal edge, and enables them to escape from their
prison. In _Blatta germanica_ the female is believed to help in the
process of extrication.[24] The larvæ are at first white, with black
eyes, but soon darken. They run about with great activity, feeding upon
any starchy food which they can find.
[24] Hummel, loc. cit.
[Illustration: Fig. 5.--Egg-capsule of _P. orientalis_ (magnified). A,
external view; B, opened; C, end view.]
The larvæ of the Cockroach hardly differ outwardly from the adult,
except in the absence of wings. The tenth tergum is notched in both
sexes, as in the adult female. The sub-anal styles of the male are
developed in the larva.
Cornelius, in his Beiträge zur nähern Kenntniss von Periplaneta
orientalis (1853), gives the following account of the moults of the
Cockroach. The first change of skin occurs immediately after escape
from the egg-capsule, the second four weeks later, the third at the end
of the first year, and each succeeding moult after a year’s interval.
At the sixth moult the insect becomes a pupa,[25] and at the seventh
(being now four years old) it assumes the form of the perfect Insect.
The changes of skin are annual, and like fertilisation and oviposition,
take place in the summer months only. He tells us further that the
ova require about a year for their development. These statements are
partly based upon observation of captive Cockroaches, and are the
only ones accessible; but they require confirmation by independent
observers, especially as they altogether differ from Hummel’s account
of the life-history of _Blatta germanica_, and are at variance with the
popular belief that new generations of the Cockroach are produced with
great rapidity.
[25] The use of the term _pupa_ to denote the last stage before the
complete assumption of wings in the Cockroach, is liable to mislead.
There is no resting-stage at all; wings are developed gradually,
and are nearly as conspicuous in the last larval state as in the
so-called pupa. There seems no reason for speaking of pupæ in this
case.
It is preferable to designate as “nymphs” young and active Insects,
immature sexually, but with mouth-parts like those of the adult. See
Lubbock, Linn. Trans., 1863, and Eaton, Linn. Trans., 1883.
[Illustration: Fig. 6.--Young nymph (male). × 6.]
The antennæ of the male nymph resemble those of the adult female. Wings
and wing-covers appear first in the later larval stages, but are then
rudimentary, and constitute a mere prolongation of the margins of the
thoracic rings. Cornelius says that the round white spot internal to
the antenna first appears plainly in the pupa, but we have readily
found it in a very young larva. The Insect is active in all its stages,
and is therefore, with other Orthoptera, described as undergoing
“incomplete metamorphosis.” After each moult it is for a few hours
nearly pure white. Of the duration of life in this species we have no
certain information, and there is great difficulty in procuring any.
[Illustration: Fig. 7.--Older nymph (male) with rudiments of wings.
× 2-1/2.]
_Sexual Differences._
Male Cockroaches are readily distinguished from the females by the
well-developed wings and wing-covers. They are also slighter and weaker
than the females; their terga and sterna are not so much thickened;
their alimentary canal is more slender, and they feed less greedily
(the crop of the male is usually only half-full of food). They stand
higher on their legs than the females, whose abdomen trails on the
ground. The external anatomical differences of the sexes may be
tabulated thus:--
_Female._ | _Male._
|
Antenna shorter than the body, | Antenna rather longer than
the third joint longer than | the body, the third joint
the second. | about as long as the second.
|
Wings and wing-covers rudimentary. | Wings and wing-covers well
| developed.
|
Mesosternum divided. | Mesosternum entire.
|
Abdomen broader. | Abdomen narrower.
|
Terga 8 and 9 not externally | Terga 8 and 9 externally
visible. | visible.
|
The 10th tergum notched. | The 10th tergum hardly
| notched.
|
The 7th sternum divided behind. | The 7th sternum undivided.
|
The external outlet of the | The outlet between the 10th
rectum and vulva between | tergum and the 9th sternum.
the 10th tergum and the |
7th sternum. |
|
No sub-anal styles. | Sub-anal styles.
_Parasites._
We have before us a long list of parasites[26] which infest the
Cockroach. There is a conferva, an amœba, several infusoria, nematoid
worms (one of which migrates to and fro between the rat and the
Cockroach), a mite, as well as hymenopterous and coleopterous Insects.
The Cockroach has a still longer array of foes, which includes monkeys,
hedgehogs, pole-cats, cats, rats, birds, chamæleons, frogs, and wasps,
but no single friend, unless those are reckoned as friends which are
the foes of its foes.
[26] See Appendix.
_Names in common use._
A few lines must be added upon the popular and scientific names of
this insect. Etymologists have found it hard to explain the common
English name, which seems to be related to _cock_ and _roach_, but
has really nothing to do with either. The lexicographers usually hold
their peace about it, or give derivations which are absurd. Mr. James
M. Miall informs us that “_Cockroach_ can be traced to the Spanish
_cucarácha_, a diminutive form of _cuco_ or _coco_ (Lat. _coccum_,
a berry). _Cucarácha_ is used also of the woodlouse, which, when
rolled up, resembles a berry. The termination _-ácha_ (Ital. _-accio_,
_-accia_) signifies _mean_ or _contemptible_. The Spanish word has also
taken a French form; at least _coqueraches_ has some currency (see,
for example, Tylor’s Anahuac, p. 325).” In provincial English _Black
Clock_ is a common name. The German word _Schabe_, often turned into
_Schwabe_, means perhaps _Suabian_, as Moufet, quoting Cordus, seems
to explain.[27] _Franzose_ and _Däne_ are other German words for the
insect, applied specially to _Blatta germanica_; and all seem to imply
some popular theory as to the native country of the Cockroach.[28]
This etymology of _Schabe_ is not free from suspicion, particularly
as the same term is commonly applied to the clothes-moth. _Kakerlac_,
much used in France and French-speaking colonies, is a Dutch word of
unknown signification. _P. Americana_ is usually named _Kakerlac_ or
_Cancrelat_ by the French; while _orientalis_ has many names, such
as _Cafard_, _Ravet_, and _Bête noire_.[29] The name _Blatta_ was
applied by the ancients to quite different insects, of which Virgil and
Pliny make mention; _Periplaneta_ is a modern generic term, coined by
Burmeister.
[27] Insectorum Theatrum, p. 138. The name _Schwabe_ is frequent in
Franconia, where it is believed to have taken origin. Suabia adjoins
Franconia, to the south.
[28] Compare the Swedish name (_supra_, p. 18).
[29] A fuller list of vernacular names is given by Rolland, Faune
Populaire de la France, Vol. III., p. 285. See also Nennich,
Polyglotten Lexicon, Vol. I., p. 620.
_Uses._
Of the uses to which Cockroaches have been put we have little to
say. They constitute a popular remedy for dropsy in Russia, and both
cockroach-tea and cockroach-pills are known in the medical practice of
Philadelphia. Salted Cockroaches are said to have an agreeable flavour
which is apparent in certain popular sauces.