1902 Encyclopedia > Arachnida > Arachnida - Order VII: Araneidea - Classification

Arachnida
(Part 28)



(28) ARACHNIDA - ORDER VII: ARANEIDEA - CLASSIFICATION

CLASSIFICATION. - It is impossible within our remaining space to go into detail upon this wife portion of the subject; it must suffice to say that the order Araneidea may at present be divided into about thirty-two families. These are -Theraphosides, Colophonides, Filistatides, Ceconiides, Tetrablemmides, Dysderides, Drassides, Palpimanides, Dictunides, Agelenides, Hersilides, Scytodides, Pholcides, Theridiides, Phoroncidides, Epeirides, Gasteracanthides, Uloborides, Miagrammopides, Poltides, Thlaosomites, Arcydes, Stephanopides, Eripides, Thomisides, Podophthalmides, Lycosides, Sphasides, Dinopides, Salticides, Myrmecides, Aphantochilides. In these families are comprised about tow hundred and sixty genera based upon special details of structure; principally the position of the eyes, the form of the maxillae and labium, the number and structure of the spinners, and some other details. The species are very numerous; probably not a tithe of the existing ones are yet described. On one family alone, Salticides, nearly a thousand are known.

As in all other creatures, differences of colour and markings, as well as integumental clothing and armature, serve to distinguish the species-the latter, too, are at times of generic value; but with regard to spiders particularly, in order to determine theirs species, it is very essential to obtain comparative dimensions from different portions of structure; thus the position of the eyes on the fore part of the caput furnishes us with the facial space (or the space between the margin of the caput just above the falces and the posterior eyes nearest to the medial line), and the clypeus, or the space between the same (fore) margin of the caput and the anterior eyes nearest to the medial line. The comparative extent of these parts is of great importance as specific characters, and they are easily observed; that part of the facial space occupied by the eyes is concisely described as "the ocular area." The relative and comparative length, again, of the legs, and of their different joints, are strong specific characters, the first also generic. Male spiders when adult may, with few exceptions, be certainly distinguished in regard to their species, by the form and structure of the palpi and palpal organs, the development of the latter being an infallible criterion of maturity. Female spiders, again, may, numerous cases, be as certainly distinguished by the form and structure of the genital aperture, situated in the medial line beneath the fore extremity of the abdomen; this aperture is never externally "perforate" until the last moult of the spider, and its full development is therefore an unerring criterion of the maturity of the female sex. With respect to the senses of spiders-smell and hearing - nothing appears to have been certainly ascertained; but the late Mr Richard Beck has an interesting paper upon the subject in Entomologist, Lond. 1866, vol. iii. p. 246. He suggests that the fine and delicate hairs of some spiders' legs may convey sounds to them. with regard to the sense of taste we may well conclude that spiders have this sense in considerable perfection, in the possession of a well-developed membranous tongue.





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