REVISION OF STREPSIPTERA PIERCE. 45 



The other prominent conditions of host biology may be best 

 glanced over by quoting four paragraphs from Saunders (1850), in 

 which he discusses the bearing on the parasites. 



Polistes. — 



It is well known that among wasps neuters alone are produced up to a certain period, 

 upon which the duty subsequently devolves of preparing the cells set apart for females; 

 and the Xenos being essentially dependent upon the hibernation of the latter the 

 female parasite of the preceding year must either await the occasion when the cells 

 of the female wasps are so prepared for the reception of ova, or otherwise, transmitting 

 her posterity to these females through the intermedium of neuters in the first instance, 

 the Xenos would thus prove to be double-brooded. 



The statistics previously quoted concerning parasitism of Polistes 

 annularis would amply bear out this conclusion, or rather that there 

 is almost continuous breeding of the parasites throughout the summer. 



Under the peculiar embryogenous and metamorphotic conditions affecting the con- 

 tinuations of the species it is manifest that these parasites could not perpetuate their 

 existence in company with the social Vespidte unless the epoch of parturition were 

 thus protracted until the following year, so as to enable them to transfer their hexapod 

 progeny to the succeeding colony of wasps. 



This conclusion is proven by the breeding of male parasites from 

 Polistes annularis in October and the fact that all of the fall female 

 parasites were but just mature and that the eggs had just begun to 

 form. Male parasites are probably rarely carried through the winter 

 on account of the unusual debilitating influences felt by the hosts 

 bearing them. 



Andrena. — 



In the case of Stylops, * * * the necessity exists for the rapid development 

 of the ova, the Andrense enjoying but a limited term of existence at large, and it 

 being therefore essential that within the brief period of a few weeks the female para- 

 site should fulfill the part assigned her and the young hexapods be ready to occupy 

 their appointed stations in the larva cells of the bee, soon about to be closed. 



In the case of Andrena hibernation is probably mainly in the im- 

 mature stage in both host and parasite. 



Prosopis. — 



A. corresponding urgency is imposed upon these parasites on Hylseus, although the 

 larva state of the latter continuing throughout the winter and spring involves the 

 necessity of a suitable conformity of habit in the parasite. 



BIOLOGY OF THE PARASITE. 



FERTILIZATION. 



The differentiation of sexes in this order renders the subject of 

 biology one of great interest. The helpless female must lie motionless 

 in the body of its host with only the cephalothorax protruding and 

 await the coming of the active, nervous male. 



That the female must be fertilized can hardly be doubted, and yet 

 the nature of the act and the fact itself has been but slightly proven. 



