1916] Biology of Paraphelinus Speciossisimiis Girault 99 



The adults are beautiful little insects with head and abdo- 

 men almost entirely black, thorax and legs chiefly light yellow, 

 a dark band across the front wings and ovipositor exserted. 

 The females average about 0.8 mm. long; the males, about 

 0.5 mm. 



This species is a primary multiple parasite of the Hessian 

 Fly. It has been demonstrated repeatedly that it is a primary 

 parasite, not only by rearing it from the Hessian Fly, but by 

 experimentally parasitizing Hessian Fly puparia known to be 

 free from parasites. It would seem to promise much as a pri- 

 mary parasite of this host because several adults usually emerge 

 from a single host. This is not due to polyembryony but to 

 multiple egg deposition, as shown by the recovery by dissection 

 of eggs deposited in puparia. The number of adults emerging 

 from a puparium varies from 1-10, with an average of about 7, 

 for puparia experimentally parasitized. This average is consid- 

 erably lower under field conditions as they obtained last year. 

 Eleven eggs have been dissected from one host parasitized in 

 the laboratory, and another contained twenty-one living larvae, 

 two dead larvae and two dead eggs. In this case the evident 

 excessive parasitization had already begun to right itself. 



The adults emerge through a round hole in the middle 

 region of the puparium, and usually there is a single one. 

 Sometimes two exit holes are cut, and occasionally three. When 

 there is a single exit hole it is frequently much larger than would 

 seem necessary. The exit holes vary in size from 0.2 mm. to 

 0.45 mm. with an average for ten puparia of 0.33 mm., while 

 according to measurements made by Mr. Myers the largest 

 diameter of the thorax averaged 0.24 mm. for the females, while 

 in the males it is only 0.18 mm. 



All adults usually emerge from a puparium about the same 

 time, but occasionally they may emerge throughout the day, 

 and in one case the last female emerged two days later than the 

 others. In many cases both sexes emerge from the same 

 puparium. In laboratory cages where both sexes were intro- 

 duced, about 18% of the progeny were males. In one cage into 

 which only unfertilized females were placed, all of the progeny 

 were males. It is apparent from this that the species is 



