Spiders

by Cecil Warburton

We have said that Lycosid spiders see comparatively well; yet, if they are placed within an inch or two of their cocoons they may be quite a long time finding them. This is very puzzling until it is considered that its habitual position is such that the spider never sees it. She never has seen it since its construction, and does not in the least recognise it by sight. Spiders of other groups, where the female remains near but detached from the cocoon, are not at the same disadvantage, and if the cocoon is removed to a short distance the mother will go straight to it and bring it back. The wolf-spider only knows the feel of the cocoon; she may pass close by it without recognition, but as soon as she touches it the cocoon is immediately resumed—if the interval of separation has not been too great.

But is it necessary to restore to the spider her own cocoon? Will not that of another spider serve as well? Certainly it will; a wolf-spider will eagerly adopt the cocoon of a spider even belonging to a different genus, if not greatly unlike her own in size. Nay, even a ball of pith of the same size will be attached with alacrity to the spinnerets, though if offered a choice between a cocoon and a pith ball the spider, after some hesitation, selects the real article. One spider even accepted a cocoon into which a leaden shot had been inserted, making it many times its original weight. She could hardly crawl with her new burden, but stuck to it gallantly, and when several efforts to secure it to her spinnerets had proved ineffectual she carried it about between her jaws and the third pair of legs. Again we find the intelligence of the spider distinctly limited, but its powerful instincts are equal to all ordinary requirements. Nature does not, as a rule, play extravagant pranks, such as interchanging cocoons or substituting for them pith balls and leaden pellets.

The famous Tarantula is a wolf-spider, though in America, unfortunately, the name has been quite wrongly applied to the members of an entirely different group. Everyone has heard of its deadly repute, and of the myth that its bite can only be cured by the wild tarantula dance or tarantella. It is one of the large Lycosids of southern Europe. These, as we have said, are much less nomadic than the smaller species, but have a permanent home, from which they do not wander far afield. They prefer waste, arid places, and their burrows are simple cylindrical tubes with the upper portion lined by silk, the mouth being often surmounted by a sort of rampart of particles of soil mingled with small pieces of wood collected in the neighbourhood. The spider lurks in the mouth of the tube where its glistening eyes can be distinctly seen. If an insect ventures near it rushes out and secures it; if alarmed, it retreats instantly to the bottom of the burrow.

That most fascinating of all entomological writers, J. H. Fabre, made some observations on a tarantula of southern France which well deserve attention. Colonies of the spider were numerous in his neighbourhood, and he set himself to procure some specimens. Old writers assert that if a straw be inserted into the burrow the spider will seize it and hold it so firmly that it may be drawn forth. Fabre found this method exciting, but uncertain in its results. Another plan which had been advocated was to approach warily and cut off the retreat of a spider by plunging the blade of a knife into the soil below it and so cutting off its retreat, but this required very rapid action, and was, moreover, apt to be prevented by the presence of stones in the soil. He devised a new scheme. He provided himself with a number of “bumble” bees in narrow glass tubes—about the width of the spider burrows. Repairing to a tarantula colony he would present the open end of the tube to the mouth of a burrow. The liberated bee, seeing a hole in the ground exactly suitable for its own purposes, would enter it with very little hesitation. There would be a loud buzz and then instant silence. Inserting a pair of forceps into the hole, Fabre would then withdraw the bee with the spider clinging tenaciously to it. In all cases the death of the bee was instantaneous, though the closest examination of its dead body revealed no wound.

Now Fabre was fresh from his wonderful studies of the habits of the solitary wasps, which provide their young with insects stung in such a way as to cause paralysis but not death. In their case the problem was to secure food for their larvae which should remain fresh for many days, an instinct taught them to solve it in the most remarkable manner. The problem of the spider was different. It was a case of killing instantly, or being killed; a merely wounded bee is as formidable as one unharmed. What Fabre desired to know was this: did the spider trust to one invariable deadly stroke in dealing with the bee, as the solitary wasp, according to its species, had been found to act always precisely in the same way in paralysing its victim?

To settle this point the spider must be seen at work, and the obvious plan seemed to be to enclose a bee and a tarantula in a glass vessel and see what would happen. But nothing happened at all. The spider, away from its burrow, refused to attack. The equally matched antagonists treated each other with the greatest respect and only evinced a desire to keep as far apart as possible. Even when placed in the same tube both acted on the defensive, and no light was thrown on the problem.

But Fabre’s ingenuity was equal to the occasion. It occurred to him that to use as a bait an insect of burrowing habits had been a tactical error; if instead of a bumble bee some other insect, equally formidable, but not attracted by holes in the ground, were selected for the purpose, the spider might be induced to rush forth and reveal its method of attack.

A large carpenter bee—Xylocopa—was chosen and the mouth of the tube containing it was presented as before to the mouth of the tarantula tunnel. The insect showed no disposition to enter the tunnel, but buzzed in the tube outside. Many burrows were tested before any luck attended the investigator, but at length a spider responded. There was a fierce rush, a clinch, and the bee was dead; the operation was too rapid to follow, but the spider’s fangs remained where they had struck—embedded just behind the insect’s neck. The experiment was repeated until sufficient cases had been witnessed to establish the fact that the tarantula dealt no random stroke but with unerring precision and lightning rapidity plunged its fangs into the vital spot. Fabre quaintly exclaims “J’étais ravi de ce savoir assassin; j’étais dédommagé de mon épiderme rôti au soleil!”

Examples of the same species of tarantula kept in captivity threw further light of the habits of the group. These large Lycosids live for years, and though stay-at-homes when rangé so-to-speak, they are at first wanderers on the face of the earth. They do not settle down and burrow till the autumn just after they have attained maturity. These young adults are only about half the size they will eventually attain, but the burrows are enlarged at need, so that it is customary to find tubes of two sizes—those of the newly established small females, and those of the fully-grown females of two or more years old.