CHAPTER XV

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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