-10- 



Genus Hydroptila Dalman 1819 



At present the largest genus in the family Hydroptilldae com- 

 prised of sixty species. This genus may be recognized readily as 

 possessing a spur formula of 0-2-4 and in lacking ocelli. In ad- 

 dition the males have "scent caps" or eversible glands on the dor- 

 sal area of the head. Although these "scent caps" are probably 

 diagnostic, very little work has been done on them. Mosely (1919, 

 1923, 1924) has studied a few species. Most of the studies have 

 been on the male genitalia, in fact the genitalia are the basis 

 for determining Trichoptera. In the Hydroptila , two groups may be 

 separated by the shape of the 7th sternite process (figs. 32 & 33); 

 one has a short pointed process and the other a long and blunt one. 

 The male claspers, tenth tergite and the aedeagus are quite dis- 

 tinct for each species. 



Species that are quite similar such as Hydroptila arctia 

 Ross - JH. consimilis Morton have some overlap in their distribution 

 but the first is more western and the latter one more eastern in 

 distribution. Two other similar species Hydroptila hamata Morton 

 and H. modica Mosely have distributions that overlap but here the 

 former is more eastern than the latter, these two are more diffi- 

 cult to separate. The three H. icona Mosely, U. ajax Ross and H. 

 pecos Ross are quite alike. H. icona occurs in Mexico and south 

 central U.S.A., II. pecos as a species also occurs in south-central 

 U.S.A. and more northward into Colorado and Wyoming. H. a.jax is 

 more eastern and northward in its occurrence but does extend into 

 areas where the others occur. The 10th tergites of the three are 

 distinctive - E. a.jax - is divided into lateral and mesal sclero- 

 tized "fingers," with membranous strips between them. II. icona has 

 an emarginate 10th tergite, H. pecos is entire. The relative 

 length of the claspers are: H. a.jax - longest, H. icona - inter- 

 mediate, E. pecos - shortest. However, care should be taken in de- 

 termining these animals. 



Text Figure 1. Hydroptila cf genitalia. H. broweri . 2A lateral, 

 2C ventral; 10 = tenth tergite, sp = subgenital 

 plate; cl = clasper. 



