122 AMERICAN SPIDERS 



some common feminine name, when suddenly its true sex becomes 

 manifest. The males are much darker than the brownish females, 

 often nearly black, and have an abdomen set with rusty red hairs. 



Their final transformation gives the males an entirely different 

 outlook on life. Whereas they have been content for years to live 

 in a dark burrow, they now desert it and wander over the country- 

 side in search of mates. This activity occurs late in the year, from 

 July into November, and during this period they may be seen cross- 

 ing the highways of the Southwest, frequently in considerable 

 numbers. 



Most of the tarantulas observed wandering in the open are males, 

 and these are seen only during mating season. Few survive the year 

 in which they become mature; many die a natural death, others are 

 killed by the female during courtship or after mating. It is quite 

 different with the females, whose unusual longevity has been pre- 

 viously noted. 



Living to a ripe old age is quite an accomplishment, for taran- 

 tulas are plagued by many enemies. Various rodents dig into their 

 burrows, and, unmindful of the poisonous hairs, use the spiders for 

 food. The young are preyed upon by many birds, and lizards, frogs, 

 and toads, and some snakes find them quite suitable dietetically. 

 Insidious enemies are the small-headed flies of the family Acroceri- 

 dae known to confine their attentions exclusively to spiders, in the 

 bodies of which they develop as voracious maggots. The species 

 of Pepsis, giant metallic blue or greenish digger wasps with rusty 

 wings, specialize in tarantulas, in fact occur only where these large 

 spiders are found. Preferred prey because of their greater bulk, the 

 females offer a far more generous supply of nutritional food to this 

 predator than do the males. The long legs of the male seem to give 

 him some degree of safety, and when he elevates his body high on 

 his legs, the "tarantula hawk" has such difficulty in stinging him 

 that she may abandon her efforts. 



On those occasions when the female tarantula ventures forth 

 during the day, she is fair game for the great tarantula hawks 

 (Plate 12 and Plate XVII). The details of the ensuing struggle, 

 quite as unequal as in the case of the trap-door spiders, are given 

 by Petrunkevitch: 



The Pepsis comes deliberately to the tarantula on the side 

 of the cage and drives her down to the ground. The next mo- 

 ment she closes in on her victim in the manner already de- 



