74 AMERICAN SPIDERS 



the semen. The presence of the female is not a necessary adjunct 

 of the act, which is implemented by internal factors, whereas later 

 on she, or her threads, become the stimuli which result in the 

 mating. 



COURTSHIP 



Inasmuch as the young male leads the same kind of life as the fe- 

 male, and lives in similar webs on plants or hides in similar places on 

 the ground, maturity finds him not far distant from female neigh- 

 bors. After he has prepared himself for mating by charging his 

 palpi, a new impulse sends him in search of a female of his species, 

 and he moves about in a random manner until he is able to detect 

 his mate. 



Since spiders are largely creatures of touch, it is not surprising 

 that to find the female he relies mainly on the fine sensory hairs 

 that clothe his body and appendages. Contact with the substratum 

 brings him something more than the mere mechanical sensation of 

 touch or tension or vibration. Accompanying it is an ability to dis- 

 tinguish certain chemical substances with which his hairs come in 

 contact; this combined sense is called chemotactic. The receptors 

 for it have not been recognized, but it seems reasonably certain that 

 some of the hairs on the appendages are sensillae that respond to this 

 type of stimulation. Since the sensation comes to the spider only 

 when in actual contact with chemical substances, it is nearer that 

 of "taste" than "smell," but it remains a quite different sense from 

 any possessed by man. The male spider thus becames keenly aware 

 of the presence of a mate through the touch of her threads, or of 

 the trail she leaves on the substratum, or of her actual body. 



There is still another way in which some spiders are able to dis- 

 cover their mates. The vagrant spiders have developed eyes of such 

 acuity that they can see moving objects at a considerable distance 

 for a spider and can identify the other sex when still several inches 

 away. In these relatively long-sighted types, and especially in the 

 jumping spiders, recognition of the female may be possible by sight 

 alone, without any aid from the chemotactic sense. On the other 

 hand, certain of the wolf spiders, having vision nearly on a par with 

 the jumpers, nevertheless appear to require both sight and touch to 

 incite pairing. 



Once the male has dicovered the female, he is on the threshold 

 of realizing the racial instinct for which he has become specialized 



