16 BULLETIX 416^ U. S. DEPARTMENT OF AGEICrLTUEE. 



they are at hand, but that impregnation occurs but once. Von Han- 

 stein (1902), writing of a European form, records many details which 

 agree with those exhibited by the American form. Males are often 

 observed waiting on quiescent deutonymphs, which they excitedly 

 stroke and overrun, as though trying to assist in the molting process. 

 A typical case of copulation may be described as follows: The female, 

 issuing from her deutonymphal skin is inamediately attended by one 

 or more males. The female remains comparatively quiet and the 

 male crawls directly under her from behind. The legs I of the male 

 are reached up around the hind portion of the female's abdomen, and 

 the tip of the male's abdomen is then bent sharply upward and slightly 

 forward (fig. 4) until the genital aperture of the male comes in con- 

 tact with the vulva, which is sub terminal. At the approach of a sec- 

 ond male the engaged individual usually "backs out" from under the 



Fig. 4. — Outline sketch of male red spider, showing the characteristic copulatory attitude with reflexed 

 abdomen. (Drawn with camera lucida. 175.) (Original, i 



female and upon the departure of the intruding male resumes his for- 

 mer position. 



Parthenogenesis. — Perkins recorded that females readily deposit 

 eggs upon failure to mate and that from these unfertilized eggs only 

 males develop. He also states that, after producing a number of 

 eggs, if inipregnated subsequently, such females produce a majority 

 of female eggs. Banks (1900) says that the first eggs laid by unfer- 

 tilized females ' ' produce only males, which, when adult, will pair with 

 the females, and the latter will then lay eggs producing both sexes.'' 

 Morgan detennined that eggs from unfertilized females were viable 

 and capable of development. Ewing reared to adult 52 eggs of three 

 virgin females and all of them became male. 



While it has been known that unfertilized eggs become male indi- 

 viduals, no effort has been made, apparently, to test the potency of 

 agamic males. Upon a few occasions parthenogenetic males have 

 been isolated with virgin females, which deposited the usual number 



