THE HUNTING SPIDERS 225 



compensation for weak chelicerae, the small crab spiders are for- 

 midable creatures that will attack insects and spiders much larger 

 than themselves. 



In one line of typical crab spiders, we find these characteristics: 

 elongate body, legs quite long and all about the same length, brushes 

 of hairs on the legs, and a pair of adhesive claw tufts on the tip of 

 each tarsus. The philodromids are swift runners, and move easily 

 on precipitous surfaces. For the most part they live on vegetation, 

 and they are colored to conform rather closely with the particular 

 surface on which they sit. Especially well camouflaged are the 

 running crab spiders of the genus Philodromus, which, with long 

 legs spreading far sidewise, press flat against the surface of a tree 

 or stem. The common Philodromus pernix of the northeastern 

 states, and its many close relatives, have mottled bodies that closely 

 resemble the bark of trees; and those of domestic inclination are not 

 easily discerned against the weathered boards of fences and build- 

 ings. Other species are more brightly colored, and, as in the case 

 of the widespread Philodromus rufus, prefer the colored leaves of 

 various bushes and trees, under which they attach their tiny egg 

 sacs. One of the commonest western representatives of this group, 

 Philodromus virescens, has the same bluish gray color as the sage- 

 brush on which it is most often encountered. Other philodromids 

 run on the ground, where they hide in grass or plants. Thanatus 

 climbs well, but other species hide under stones and behave like 

 running ground spiders. A tiny species of Ebo, common on the open 

 sand along the edges of streams and lakes in the Middle West, 

 matches the sand almost exactly in color; it remains unnoticed until 

 accidentally disturbed, whereupon it runs a few inches and again 

 lies perfectly still. The greatly elongated species of Tibellus, straw- 

 colored and lightly marked with dark, narrow lines, frequent the 

 grasses in meadows, lying parallel to and close against the stem. 

 Easily visible when moving, these spiders will stop suddenly and 

 appear to vanish from sight in their natural environment charac- 

 teristics that they have in common with the majority of philodro- 

 mids. 



The typical crab spiders, which most nearly resemble their 

 namesakes, are the ambushers of the subfamily Misumeninae (Plates 

 3, 9 and 27; Plate XXIX). Their short, wide bodies are supported 

 by legs of very unequal size, the first two pairs being quite long 

 and robust and the hind pairs considerably shorter and weaker. 

 The misumenids were probably derived from types similar to the 

 philodromids, but their specialization has markedly changed them, 



