. The biology of spiders. Spiders; Insects. EVOLUTION 309 The Tarsal Claws The remaining families of spiders, whether cribellate or not, which all breathe by two lung-books and a single tracheal spiracle, divide themselves broadly into those with three tarsal claws and those with two. This recalls the similar division of the Mygalomorphae and depends on the same difference in the mode of life. Like that division, too, it is not complete, for there are a few families, such as the Zodariidae and Palpimanidae, which include both two and three-clawed genera. On the whole, however, it is a convenie
. The biology of spiders. Spiders; Insects. EVOLUTION 309 The Tarsal Claws The remaining families of spiders, whether cribellate or not, which all breathe by two lung-books and a single tracheal spiracle, divide themselves broadly into those with three tarsal claws and those with two. This recalls the similar division of the Mygalomorphae and depends on the same difference in the mode of life. Like that division, too, it is not complete, for there are a few families, such as the Zodariidae and Palpimanidae, which include both two and three-clawed genera. On the whole, however, it is a convenient and probably a natural separation. The two-clawed group consists of one fossil family, the Parattidae, and fourteen recent ones, with some differences in their general modes of life. The most important families, the numerous Clubionidae and Drassidae, contain the spiders that merely wander, usually at night, without great power of speed or conspicuous ability to leap and so prey upon what they may chance to en- counter. Indeed, among the Clubio- niidae there are genera, such as Corinna, which spin the primitive form of diverg- Fig. 106.—Tarsus of ine tube-web Clubiona spiderling, ni& LUUC wcu' showing transitory The two other chief modes of life third claw. From a in this division are obvious elaborations Rh^™arneyaph ^ of simple wandering. The crab- spiders, or the family Thomisidae, often hidden by the protective colourings which have been already described, lie in wait for their prey and leap, perhaps sideways, upon it. The large Sparasside are flattened crab-like spiders, which generally conceal themselves in narrow crevices. The jumping-spiders or Salticidae have developed the habit of leaping upon their prey instead of chasing it, a method which, if one may judge from the multitude of species and world-wide distribution of this family, has certainly been very Please note that these images are extracted from scanned page images that may have been di
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