ON PARTHENOGENESIS IN SPIDERS. 1 



THOS. H. MONTGOMERY, Jr. 



The only references known to me upon the question of the 

 occurrence of parthenogenesis in araneads are the following : 

 Blackwall (1845) took young females of Tegenaria domestica, T. 

 civilis, Agelena labyrinthica, Ciniflo atrox, Drassus sericeus, The- 

 ridion quadripunctatum and Segestria senoculata and kept " most 

 of these individuals ... in captivity from one to three years after 

 they had completed their moulting and attained maturity ; yet 

 three only, an Agalena labyrinthica, a Tegenaria domestica, and a 

 Tegenaria civilis, produced eggs, and they proved to be sterile, 

 though several of the others, to which adult males were subse- 

 quently introduced, laid prolific eggs after coition." Blanchard 

 (1857) also reached the same conclusion that eggs laid by unim- 

 pregnated females prove sterile. Then Balbiani (1873) adopted 

 this conclusion, though his own observations were not decisive : 

 " Having imprisoned during a whole year several females of 

 Tezenaria domestica, I have noted that the first batches were com- 

 posed exclusively of fecund eggs, while the subsequent batches 

 contained always a variable number of sterile eggs, of which the 

 quantity increased with the batch, so that they ended in not con- 

 taining a single egg able to develop. But it is evident that if 

 these females had been gifted with the faculty of reproducing 

 without the concourse of the male, all the successive batches 

 should have been equally fecund." 



On the other hand, Campbell (1883) kept a female of Tege- 

 naria guyonii in captivity a whole year, during which she under- 

 went two moults ; then she laid eggs from which young hatched. 

 And Damin (1893) imprisoned a female Filistata testacea Latr. 

 from the spring of 1891 until the spring of 1893 ; she moulted 

 twice in the summer of 1891 and once in the spring of 1892, 

 then made a cocoon from which young spiders emerged. He 

 notes the extreme rarity of the males of this species, and asks : 

 ' Does not this absence of the male indeed indirectly cause the, 



1 Contributions from the Zoological Laboratory of the University of Texas, no. 86. 



302 



