THE EVOLUTION OF SPIDERS 101 



the ground and made little effort to establish a permanent station of 

 refuge. Food perception was accomplished by sensory leg hairs 

 which tested the terrain, for their small eyes were useful only to 

 distinguish light from darkness. These sluggish prototypes lived a 

 timeless life of leisure on the tangled jungle floor of their humid 

 swampland. Only during molting and egg laying was it desirable 

 to be concealed from wandering predators, and from less worthy 

 adversaries that under those trying circumstances might do injury 

 to the eggs or to the spiders themselves. The first step toward a 

 life of dependence on silk was the coating of the eggs with excre- 

 tory material from the abdomen, voided by coxal glands that opened 

 through the abdominal appendages. As the product of the glands 

 became more suitable for use as a gluing and covering agent, and 

 the spinnerets more adept in their application of the gummy liquid, 

 greater possibilities for the use of the crude silk opened on all sides. 



These early spiders were perennials. Each female produced and 

 cared for many egg masses during her life with varying degrees of 

 efficiency and success. Those survived that were more adequately 

 protected by a silken cover, and guarded in long vigils by the 

 mothers, whose regard for the safety of the egg mass was being 

 tried and modified by an increasingly hostile and enterprising band 

 of predators. 



By the late Paleozoic, the two principal groups of spiders known 

 today had been developed: the My galomorphae , or tarantulas and 

 their allies; and the Araneomorphae, the true spiders. Discretely 

 separated even in the coal measures, these two lines have grown up 

 side by side. In many respects their accomplishments have paralleled 

 each other, a natural development since both were originally en- 

 dowed with similar equipment and potentialities. However, for 

 various reasons, the true spiders surpassed the tarantulas during the 

 Tertiary and became the dominant group. 



THE TARANTULAS 



Our first sight of the typical mygalomorph spider is in the coal 

 measures, where we find it little changed from the ancestral spider 

 that preceded it. During the Paleozoic Era, when much of North 

 America was a dismal, swampy area covered by great forests of 

 strange plants and trees, there lived in the region of modern Illinois 

 primitive spiders whose abdomens were armored with hardened 



