No one is unfamiliar with the orbicular snares, the structure of which has already been described with some minuteness (see p. 344), and some of the spiders which construct them are among the best known members of the order.
It is impossible here to deal with the multitudinous forms embraced by this family. We must mention those genera richest in species, and some others of special interest. It will be convenient to indicate eight sub-families or groups, which include most of the forms likely to be met with. These are the Theridiosomatinae, Tetragnathinae, Argiopinae, Nephilinae, Epeirinae, Gasteracanthinae, Poltyinae, and Arcyinae.
(i.) The Theridiosomatinae are a small group which might with equal propriety be classed with the Theridiidae or the Epeiridae. Theridiosoma argenteolum is a rare spider in Dorsetshire. It is a minute spider, one-twelfth of an inch in length, with silvery white globular abdomen variegated with reddish brown, and yellow cephalothorax with darker caput. Some allied spiders spin a roughly circular snare.
(ii.) The Tetragnathinae consist chiefly of two genera, Pachygnatha and Tetragnatha. The first consists of spiders which are not orb-weavers, but live in herbage, especially in swampy places. Two species, Pachygnatha clerckii and P. degeerii, are common in England, and a third, P. listeri, is sometimes met with. They are rather striking, prettily marked spiders, with strongly developed chelicerae.
The species of Tetragnatha are true orb-weavers, and may easily be recognised by their cylindrical bodies, elongated chelicerae, and long legs, stretched fore and aft along the rays of their webs. Five species have been recorded from England, and the genus contains at least a hundred species in all; almost every country in the world, regardless of its latitude, supplying examples.
Simon associates with these spiders the genus Meta, which includes perhaps our commonest Epeirid, Meta segmentata, a smallish and not very striking Orb-weaver, with a rather elongated or subcylindrical abdomen. Every garden is pretty sure to abound in it.
(iii.) The Argiopinae include many large and very striking members of the Epeiridae. There are about a hundred species of Argiope (Fig. [198], p. 379) spread over the tropical and sub-tropical countries of the world. They rarely invade the temperate regions, but A. bruennichi is found in South Europe, and A. trifasciata in Canada. The large spiders with transverse bars of yellow or orange on their abdomen, and often with a silvery sheen, belong to this genus. The species of the allied genus Gea are generally much smaller, and their abdomen more elongated. Both genera are found in tropical and sub-tropical regions all over the world. Argiope always sits in the middle of its circular web. There are invariably some flossy zigzag bands of silk stretched between two of the rays, and the web is generally accompanied by an irregular net on its border, where the much smaller male may be found.
(iv.) Among the Nephilinae are to be found the largest Epeirids. Indeed, the largest yield in size only to the Aviculariidae. Nephila is a tropical genus, numbering about sixty species. The abdomen is generally elongated and somewhat cylindrical, and is strikingly variegated. It is in this group that the disparity in size between the sexes is most marked (see p. [379]).
(v.) The Epeirinae[[320]] include the bulk of the Orb-weavers, and form a very extensive group. Five genera and twenty-eight species are in the British list.
No spider is more familiar than Epeira diademata (Fig. [181], p. 325), the Garden-spider, par excellence, which attains its greatest size and spreads its largest snares in the autumn. The smaller and much less conspicuous Zilla x-notata is sure to be found abundantly in the same locality. Several other Epeirids are to be found in this country, especially in the south, by sweeping heather or bushes with a net, or shaking the boughs of trees over an umbrella or other receptacle. The little apple-green species is Epeira cucurbitina. E. cornuta is extremely common in marshy places all over the country. In furze bushes, and often among sedge in swampy places, will frequently be found E. quadrata, one of the largest and handsomest species we possess. The ground-colour may vary from orange-red to green, and there are four conspicuous white spots on the abdomen. The tent-like retreat which this spider makes near its snare often catches the eye.