THE CANADIAN ENTOMOLOGIST 217 



A KEY TO THE FAMILIES OF TRICHOPTEROUS 



LARV/E.* 



BY JOSEPH KRAFKA, JR.. LAKE FOREST, ILL. 



The larvae of the caddis-flies are among the most common of 

 aquatic forms; they are most interesting in their habits, and they 

 are of undoubted economic importance; but their study is greatly 

 retarded by the fact that there is available no means of determining 

 them even approximately. The larva^ of the European fauna have 

 been dealt with adequately by Ulmer, Siltala, Klapalek, Struck, 

 Thienemann, and other European entomologists. While no 

 thorough-going attempt has been made to trace the natural re- 

 lationships in larval characters, the European genera and species 

 can at least be recognized by keys of a more or less artificial char- 

 acter. Even this cannot be done for American genera, since the 

 only species described are some eighteen by Vorhies in his excellent 

 paper, t However, a key to the families is possible and shoufd 

 prove serviceable, as none has so far appeared in English. Fol 

 the key here offered, that of Ulmert has been used as a basis, bur 

 the whole ground has been covered in an independent study ot 

 American material. 



Reference to the figures should make the distinctions of the 

 key clear, but perhaps the terms "thysanuriform" and "cruciform" 

 as used in the order may be more fully explained. In the Trich- 

 optera, those larvae are designated as thysanuriform that have 

 the long axis of the head in line with the long axis of the body, 

 the abdomen dorso-ventrally compressed and the depressions 

 between the segments deep. In the cruciform type, the long axis 

 of the head is at a decided angle with the long axis of the body, 

 the abdomen is cylindrical and the strictures between the segments 

 shallow. The sub-eruciform type is intermediate between thysan- 

 uriform and eruciform. 



*This key is prepared as a contribution to Dr. Betten's forthcoming mono- 

 graph in which the structure of all the stages of Trichoptera is dealt with, and 

 in which descriptions of all the American genera and of all eastern American 

 species are included. 



tVorhies, Dr. Charles T., Studies on the Trichoptera of Wisconsin. Trans. 

 Wis. Acad. Science Arts and Letters, Vol. XVI, Part 1, No. 6, 1909, pp. 647-738, 

 pis. LII-LXL 



JUlmer, Dr. Georg, Trichoptera in Brauer's Die Siisswasserfauna Deutch- 

 lands, Heft 5 u. 6, 1909. Key to larvae, pp. 213-217. 

 July, 191.5 



