INTRODUCING SPIDERS 3 



The female bolas spider (Pis. Ill and XXIII) is a plump creature, 

 about one-half inch long and equally wide, which sits placidly on 

 a twig, simulating with considerable faithfulness a bud, a nut, a 

 snail, or even a bit of bird dung. What about her mate? He is an 

 insignificant atom no larger than the head of an ordinary pin. Pre- 

 cociously developed, he walks out of the egg sac fully mature, along 

 with sisters his own size who are just beginning their life and must 

 wait weeks and increase tremendously in size before they become 

 sexually mature. 



Spiders and their relatives are ancient animals; they were among 

 the first creatures to leave the waters for a life on land. Some mod- 

 ern spiders seem to be only thinly masked replicas of creatures that 

 were living in the northern hemisphere during the remote Paleozoic 

 Era, when the coal measures were still in infancy. Although more 

 generalized than the commoner true spiders, the tarantulas and their 

 kin have become specialists in their own fashion, and have devised 

 new and extraordinary ways of living in a world of competition. 

 The purse-web spiders live in a long silken tube closed at both ends, 

 and have developed long fangs with which they impale insects that 

 walk over their cylinder by biting through it. The burrowing taran- 

 tulas of the genus Antrodiaetus ensure privacy in their burrow home 

 by pulling two flaps of silk, which fit like folding doors, over the 

 entrance. The trap-door spiders are accomplished burrowers and 

 cap the opening to their chamber with a hinged trap-door. One of 

 the strangest trap-door spiders is Cyclocosmia, which has an ab- 

 domen hardened and rounded behind to form a plug with which it 

 at one time was reputed to close its burrow. 



Among the vagrant tarantulas are some that have become verita- 

 ble giants far exceeding most insects in bulk and rivaling in size even 

 the great black scorpions of Africa. Armed with long, strong fangs, 

 they are able to kill with ease and feed on frogs, toads, and lizards, 

 and also to subdue and eat rattlesnakes and other larger animals. 

 Some of the arboreal tarantulas are known to kill small birds, and 

 have gained one of their common names of "bird spiders" from this 

 activity. Longer-lived than any terrestrial invertebrate are some of 

 the great hairy tarantulas, which do not become sexually adult until 

 eight or nine years old and are known to live thirty years. 



Among the true spiders are the diurnal jumping spiders; these 

 actively pursue their prey over the ground and on plants. Special 

 tufts of adhesive hairs on the tarsi allow them great freedom of 

 movement on precipitous surfaces, and, aided by the keenest eye- 



