46 ILLINOIS BIOLOGICAL MONOGRAPHS 1166 



yielding 31 parasites. In collections of the same species made near the 

 shore 154 males yielded 35 infected specimens or an infection of 23 per cent 

 and contained 52 parasites, 276 females contained 135 infected specimens 

 or an infection of 49 per cent and yielded 377 parasites, averaging more 

 than two parasites to each infected host. During the latter part of the 

 summer 37 large nymphs were collected on the hill about two miles from 

 the lake and not a single one was found to be infected. The specimens of 

 Nemobius fasciatus were all collected near the shore. Of 15 males 8 were 

 found to be infected, yielding 16 parasites, and of 24 females only 6 were 

 infected containing 12 parasites. 



The habits of this host also make an intermediate carrier not necessary. 

 I have several times found crickets accumulated in large numbers about 

 pools of water at night. The fact that many unmated females of Para- 

 gordius varius were found in the shallow water of the lake during the early 

 forenoon, but disappeared later, indicates that infected hosts get into the 

 water and lose their parasites during the early morning. The local character 

 of the infections shows that infection takes place at or near the water's 

 edge. 



Location in the host. Early developmental stages of Paragordius varius 

 have not been found in sections of hosts. In later stages the parasites lie 

 free in the body cavity (Fig. 134). In dissections the location in the host 

 is found to be in every respect similar to that of Gordius rohustus. 



Practically no effect of the parasite on the host was found except in 

 cases of very heavy infection. In those cases a diminution in the size of 

 the reproductive organs could be detected. 



Length of parasitic period. Since experiments were unsuccessful, no direct 

 observations on the developmental period could be made, and since 

 infection took place almost uniformly thruout the summer, the time of 

 infection and time of emergence could also not be taken as criteria. The 

 earliest appearance of adult parasites in nymphs, however, produced some 

 valuable evidence on the subject. Most of the nymphs of Gryllus appeared 

 during the last week in June and Nemobius did not hatch until about a 

 week later. By the middle of August adult parasites were found in the 

 nymphs of both species. The first adult Paragordius varius from Nemobius 

 fasciatus was obtained on August 14 while the host was still a nymph. 

 The developmental period can not possibly have been more than six weeks. 

 Some of the first infected specimens of Nemobius fasciatus were obtained 

 on August 2, and the parasites at that time were mostly younger than the 

 28 day stage in Gordius rohustus. On August 12 most of the parasites were 

 of nearly adult size. 



Emergence in this species occurs in a manner similar to that in Gordius 

 rohustus. About six specimens were seen leaving their hosts. In all cases 

 the parasites emerged with the anterior end first from near the anus of the 



