SOME CONCLUDING REFLEXIONS
In the foregoing pages we have been able to deal with very few out of
the vast number of known spiders; yet the examples we have chosen for
study are fairly typical of some of the more important groups, and
calculated to give a tolerably just idea of the general economy of the
tribe. In any case even such a fragmentary study as the present gives
us food for thought. There is a question which the writer has so often
been asked that he is inclined to deal with it in anticipation, though
perhaps he is wronging his readers in supposing that they desire to
propound any such conundrum. This question is: What is the _use_ of
spiders?
Now underlying this question there is surely a very unwarranted
assumption that all the myriad creatures which exist have, as a reason
for their existence, some reference to the activities and desires of
mankind. As far as it has any meaning at all it amounts to this: What
benefit does man derive from spiders? But it seems to take for granted
that some benefits must accrue to man from these creatures, or they
would not have the audacity to persist in living. Well, if the question
in this amended form is in urgent need of an answer, the reply must
be: very little if any. Certainly spiders prey as a rule on insects
and no doubt kill many which might injure us, and in the constant
battles between man and insect pests, instances have been recorded
where particular species of spider have fought on the side of man with
appreciable effect. But then they are as likely to devour our insect
friends as our insect enemies, impartially slaying the just together
with the unjust, so that little stress can be laid on their utility on
this score. Indeed there is quite as good a case to be made out of man
benefiting spiders as of spiders benefiting man, for his architectural
proclivities have provided some species with secure homes from which
most of their enemies—except man himself—are excluded, and where they
are sheltered from the storms which are so fatal to their relatives
outside, protected from extremes of temperature, and rendered so
independent of times and seasons that the number of broods they produce
in the year has increased. Whether a creature is useful or injurious
is entirely a matter of the point of view. There are several animals
with regard to which the opinions of the farmer and the gamekeeper are
diametrically opposed!
But if anything emerges from the study in which we have been engaged,
it is surely this fact: that wherever there is a niche in nature
capable of sustaining life, to that niche some animal will sooner or
later adapt itself without any reference to man’s desires or interests.
We have seen spiders, all built on the same ground-plan, so to speak,
and with the same essential organs, so modified in the details of
structure and inherited instincts as to be able to thrive under the
most diverse conditions. Think, for instance, of the water-spider
and the desert Tarantula, or consider the difference in mode of life
between the sedentary garden-spider and the hunting Attid.
Incessant competition in the struggle for life no doubt urged on
primeval spiders to strike out new modes of existence. Under slightly
novel conditions the best adapted or most adaptable survived and
were pioneers in the occupation of a new territory till the widely
different capacities and habits which we now wonder at were slowly
evolved.
Another point to ponder on is the wonderful complexity of the instincts
which govern the actions of spiders; the extraordinary operations
they can perform, entirely untaught, and of the object of which it is
impossible to believe they are aware. We have seen that, in the most
highly organised species, the sense organs—except perhaps that of
touch—are but moderately developed, and the power of memory, the basis
of intelligent action, but feeble; yet their inherited impulses suffice
for all ordinary emergencies, and recur with unfailing precision at
the proper periods of their lives. They are machine-like, perhaps, but
what extraordinarily competent machines! The light of what we call
intelligence burns low, but a glimmer of it can be detected here and
there.
If one comes to think of it, the egg of a creature of complex instincts
is a particularly wonderful atom; it contains not only the germs of all
the complicated bodily structure, but there are bound up in it also
the impulses that are to come into play at certain definite periods
only of the spider’s life-history. And these impulses are not mere
vague reminders that now is the time to spin a snare, or to weave an
egg-cocoon; they prescribe precisely how it is to be done, involving
perhaps a dozen different spinning operations in one unvarying order.
Viewed in this light, the germ of an insect or a spider would seem
in a sense to be more complex than that of an animal whose vague
instinctive impulses are under the direction of intelligence, and can
be carried out in a variety of ways according to circumstances.
One of the most surprising things about the egg of a spider is the
amount of _energy_ stored up in it. A bird’s egg, huge in comparison,
contains material sufficient to build up the body of a fledgeling just
sufficiently active to be able to accept from the mother that first
nutriment without which it will speedily die.
But turn back to the account of the tarantula-spider. Its egg is
small—perhaps the twelfth of an inch in diameter; yet it not only
produces a spiderling complete in form, and provided with all the
complex instincts of its tribe, but there is so much energy to spare
that, for months, without any new food-supply, the young spider
can lead an active life, frequently descending from and remounting
its mother’s back, and can even put forth silk on its own account!
The objects which a conjuror produces from a hat seem trifles in
comparison with the outcome of a spider’s egg—the actual material
seems astonishing from so small a source, but whence comes all this
surprising surplus of energy? Fabre suggests that it is supplied by
the direct rays of the sun, to which the Tarantula exposes in turn all
parts of the egg-cocoon.
All through their lives spiders seem to be gifted in a high degree with
the power of extracting the utmost value, in substance and in energy,
from their food. Consider the great Theraphosid spiders—the so called
bird-eaters. They have a massive body, and great muscular power to
sustain; yet they are never heavy feeders and can go for many months
without any food at all. And it is not as though they were dormant
during this period of abstention; their vital processes seem to be
going on as usual the whole time, and they are ready at any moment
to resent attack, or to employ their spinning organs during their
long fast. True hibernation, as we have seen, does not occur in this
group; if it did, there would be nothing remarkable in the occasional
long abstention from food. The vitality of a hibernating animal is
practically at a standstill; all its vital operations—breathing,
blood-circulation, muscular action—are reduced to the lowest possible
limit, and it very likely expends no more energy during its winter
sleep than it would during a day or two of active summer life.
But of such reflexions there is no end, and many such will doubtless
arise spontaneously in the mind of the thoughtful reader, and it is for
that very reason that the study of the life-history of any animal is of
such absorbing interest. It is not contended that spiders are any more
wonderful than any other group that might have been selected. There
is, of course, a special interest attaching to the study of animals
very much nearer to man in bodily structure and mental equipment, but
the endeavour to understand the actions and appreciate the outlook on
nature of creatures far remote from man, however unsuccessful, has its
own fascination.
And this is what the mere collector entirely misses. Collecting is
of course necessary, for a complete examination is never possible in
the living specimen, and moreover without examples kept as types for
reference we should lose our way in the multitude of living forms. But
as an end in itself it is of vastly inferior value. The writer will be
well content if he has succeeded in arousing the curiosity of some with
regard to the humble life that surrounds us, and in stimulating a few
who possess the requisite keenness and patience to add to our store of
knowledge by new observations of their own.
LITERATURE
Most of the large publications on the Arachnid fauna of different
countries give some preliminary account of the habits of spiders, but
the only considerable work entirely devoted to that subject is McCook’s
_American Spiders and their Spinning-work_ (Philadelphia, 1893). A
small but interesting book on _The Structure and Habits of Spiders_
was published ten years previously by Emerton (Boston, 1883). But the
reader who wishes to pursue further the study of some point to which
his attention has been called in the foregoing pages may desire to be
referred, for fuller details, to the original papers.
Many writers have described the spinning of the circular snare,
and indeed it is quite easy for any one to watch the operation for
himself; but McCook goes into the matter in great detail and figures
many interesting variants of its normal form. J. H. Fabre’s delightful
_Souvenirs entomologiques_ (Delagrave, Paris) have been issued at
intervals for many years past, and mostly deal with insects. In
Series 9, however, he has an entertaining chapter on “Les Epeires.”
That the “viscid globules” arranged themselves mechanically was first
demonstrated by C. V. Boys (_Nature_, xl, 1889, p. 250). The same
writer experimented on the sense of hearing in spiders (_Nature_,
xxiii, 1880, p. 149). The interesting paper by G. and E. Peckham on the
mental powers of spiders is to be found in the _Journal of Morphology_
(Boston U.S.A. i, 1887, p. 403.)
The aeronautic habit has engaged the attention of many arachnologists.
Blackwall dealt with it in various papers in the _Transactions of the
Linnaean Society_ between 1833 and 1841, but the most complete account
is to be found in McCook’s original papers which are summarised in his
book already cited.
With regard to the spinning operations of _Agelena_ the reader may
consult a paper by the present writer in the _Annals and Magazine of
Natural History_, August, 1891.
The habits of the Water Spider were first described by de Lignac in
a _Mémoire_ published in 1749. Since that date many writers, notably
Wagner and Plateau, have dealt with the subject. The paper by the
last named in the _Annales des Sciences naturelles_, 1867, p. 345, is
particularly worth reading.
E. Peckham deals with “Protective Resemblances in Spiders” in the
publication of the _Natural History Society of Wisconsin_ for 1889.
The reader interested in the habits of the Wolf-spiders must certainly
consult the chapters on “La Lycose de Narbonne” in Series 9 of Fabre’s
_Souvenirs entomologiques_.
The classical account by the Peckhams, of the love dances of jumping
spiders appeared conjointly with the paper by E. Peckham on “Protective
Resemblances” cited above.
For the habits of _Atypus affinis_ (or _piceus_) the reader is referred
to the very complete account given by Enock in the _Transactions of the
Entomological Society_ (London, 1885, p. 394) of observations extending
through several years.
The larger Aviculariidae have been dealt with in various papers by
Pocock, and the particulars given with regard to _Dugesiella_ were
taken from a paper by Petrunkevitch in the _Zoologischen Jahrbüchern_,
xxxi, 1911.
In the _Archiv für Naturgeschichte_, i, 1889, Apstein published an
admirable piece of research on the structure and function of the
spinning glands of spiders. He investigated the glands present in the
various families, and the particular arrangement of the spools and
spigots on the spinnerets.
A paper by the present writer in the _Quarterly Journal of
Microscopical Science_ for April 1890 continued this investigation, and
shewed the special operations in which the various glands participated
in the case of the Garden Spider.
INDEX
Aerial flights, 32
_Agelena_, 38-46
Agelenidae, 11, 38
_Araneae theraphosae_, 87
_Araneae verae_, 87, 89
_Argyroneta_, 3, 49, 50, 51, 52
Arthropoda, 6
Attidae, 4, 33, 52, 76-87
Atypidae, 93
_Atypus affinis_, 89, 121
Balloons, 34
Banana spider, 103
Barking spider, 107
Bird-eating spiders, 25, 89, 99
Body parasites, 123
Burrows, 63
Calamistrum, 118
Cannibalism, 33, 120
Carrying the young, 73
Characteristics of spiders, 4
Chelicerae, 10, 87
Cocoon, 12, 44, 64
Cocoon of _Agelena_, 44
Crab-spiders, 52
Cribellum, 118
Crustacea, 6
_Cyclosa conica_, 28
Darwin’s Pike, 22
_Desis_, 49
Drassidae, 11
Drumming spider, 109
_Dugesiella hentzi_, 99
Educability, 22, 27, 28
Egg parasites, 121
Enemies of spiders, 120
Energy stored in the egg, 130
_Epeira_, 3, 19, 112-116, 119
_E. diademata_, 13
Eyes of jumping spiders, 78
Feet of spiders, 119
Foundation lines, 13, 14, 16, 17
Garden-spider, 2, 13, 15, 19, 20, 23, 27, 39, 78, 121, 123, 126, 128
Gossamer, 36
Habits of _Agelena_, 38
_Atypus_, 90
Jumping spiders, 79
Tarantula, 69
Theraphosid spiders, 99
Trap-door spiders, 95
Harvest spiders, 8
Hearing, 23, 101
_Heteropoda venatorius_, 37
Hibernation, 2, 131
Hub, 13, 14
Huntsman spider, 37
_Hyptiotes paradoxus_, 31
Infant mortality, 120, 121
Instinct, 21, 22, 29, 46, 129
Jumping spiders, 4, 76-87
_Linyphia_, 3, 32
Love dances, 82-87
Lung-books, 10
_Lycosa kochi_, 109
_Lycosa picta_, 61
Lycosidae, 5, 33, 52, 58-76
Mammillae, 10
Marine spiders, 49
Mental powers, 20
_Meta segmentata_, 23
Mimicry, 55-58
_Misumena_, 54
Moulting, 104, 122
Notched zone, 13, 14
_Philodromus_, 54
_Phrynarachne_, 57
_Pirata_, 59, 66
Poison of spiders, 75
Poison gland, 88
_Psalmopoeus cambridgii_, frontispiece, 103
Purring spider, 109
Rastellum, 98
Recognition of cocoons, 66
Red spider, 8
Scopula, 119
Sight, 23, 60, 81, 101
Silk glands, 111, 112
Smell, 25, 100
Solitary wasps, 124, 125
Spigots, 111, 113-116
Spinnerets, 8, 110-118
Spinning apparatus, 110
Spinning glands, 111
Spinning operations, 117
Spools, 111, 113, 114, 115
Starvation, 122
Stridulation, 25, 105
Stridulating Keys, 107, 108
Tarantula, 68-74, 128
Tarsus, 119
Taste, 26
_Theraphosa leblondi_, 94
Theraphosidae, 25, 87-104
Theridiidae, 33
_Theridion_, 3, 23, 32
Thomisidae, 33, 52
Touch, 27, 101, 102
Tracheae, 6
Trap-door spiders, 89, 94, 98
Trap-snares, 31
Use of spiders, 127
Viscid spiral, 15, 18, 19, 20, 116
Water-spiders, 48-52
Wolf-spiders, 58, 76
Zebra spider, 77
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