The spiders, to which I have hitherto adverted, seize their prey by means of webs or nets; but a very large number, though, like the former, they spin silken cocoons for containing their eggs, never employ the same material in constructing similar snares, of which they make no use.
These may be separated into two grand divisions: the first comprising those which conceal themselves and lie in ambuscade for their prey, and sometimes run after it to a short distance; the second, those which are constantly roaming about in every direction in search of it, and seize it by open violence. The former Walckenaer, in his admirable work on spiders, has designated by the name of Vagrants, the latter by that of Hunters; terming those already mentioned which spin webs and nets, Sedentaries: if to these you add the Swimmers, or those species which catch their prey in the water, you will have an idea of the general manners of the whole race of spiders.
The artifices of that tribe which Walckenaer has named vagrants are various and singular. Clubiona holosericea and many other species conceal themselves in a little cell formed of the rolled-up leaf of a plant, and thence dart upon any insect which chances to pass; while C. atrox and its affinities select for their place of ambush a hole in a wall, or lurk behind a stone, or in the bark of a tree. Aranea calycina, L. more ingeniously places herself at the bottom of the calyx of a dead flower, and pounces upon the unwary flies that come in search of honey; and A. arundinacea buries herself in the thick panicle of a reed, and seizes the luckless visitors enticed to rest upon her silvery concealment. Many of this tribe at times quit their habitations, and by various stratagems contrive to come within reach of their prey, as by pretending to be dead, hiding themselves behind any slight projection, &c. A white species I have often observed squatted in the blossom of the hawthorn or on the flowers of umbelliferous plants, and is thus effectually concealed by the similarity of colour.
Foremost amongst the spiders comprehended by Walckenaer under the general name of hunters, which search after and openly seize their prey, must be enumerated the monstrous Mygale avicularia, at least two inches long, which takes up its abode in the woods of South America, and has been reputed to seize and devour even small birds; but this is wholly denied by Langsdorf, who declares that it eats only insects[753]. This species, as well as another tropical one, Thomisus venatorius, the European Cteniza cementaria, and many others, construct in the ground very singular cylindrical cavities, and therein carry and devour their prey. These, being rather the habitations of insects than snares, I shall describe in a subsequent letter. Lycosa saccata, the species whose affection for its young I have before detailed, and not a few others of the same family, common in this country, in like manner seize their prey openly, and when caught carry it to little inartificial cavities under stones. Dolomedes fimbriatus hunts along the margins of pools; and Lycosa piratica and its congeners not only chase their prey in the same situation, but, venturing to skate upon the surface of the water itself,
"... bathe unwet their oily forms, and dwell
With feet repulsive on the dimpling well."
The Rev. R. Sheppard has often noticed in the fen ditches of Norfolk a very large spider which actually forms a raft for the purpose of obtaining its prey with more facility. Keeping its station upon a ball of weeds about three inches in diameter, probably held together by slight silken cords, it is wafted along the surface of the water upon this floating island, which it quits the moment it sees a drowning insect,—not, as you may conceive, for the sake of applying to it the process of the Humane Society, but of hastening its exit by a more speedy engine of destruction. The booty thus seized it devours at leisure upon its raft, under which it retires when alarmed by any danger.
The last of the tribe of hunters that it is necessary to particularize, are those which, like the tigers amongst the larger animals, seize their victims by leaping upon them. To this division belongs a very pretty small banded species, Salticus scenicus, which in summer may be seen running on every wall.
To Walckenaer's swimmers, the last of his grand tribes of spiders, including Argyroneta aquatica, &c., the first line of the above quotation from Dr. Darwin is particularly applicable; for these actually seize their food by diving under the water, their bodies being kept unwet by a coating of air which constantly surrounds them.—Thus one single race of insects exemplify in miniature almost all the modes of obtaining food which prevail amongst predaceous quadrupeds—the audacious attack of the lion; the wily spring of the tiger; the sedentary cunning of the lynx; and the amphibious dexterity of the otter.