Entomology of the Illinois River. 189' 



Last segment various, not as in preceding family. 

 Prothoracic appendages short, simple, situated 

 on the dorsal aspect of the thorax; 



pupa free-swiraraing Culicidm. 



Prothoracic appendages many-branched (Chi- 

 ronoraus) or simple; situated on the anterior 

 aspect of the thorax; pupa in the larval tube, 

 or resting just beneath the surface, or float- 

 ing (Ceratopogon) Chironomidm. 



These appendages short and pointed Rhyphidoe. 



Pupa in a membranous cocoon, which is taperiug 

 behind, open in the front, attached by ventral 

 surface; prothoracic appendage few- branched. 



SimuUidcB. 

 Thoracic spiracles sessile. {Brachycera.) 



Pupa enclosed in last larval skin StratiomyiidcB. 



Pupa free, not active. [Fig. 43.] TahanidcB, LeptidoB. 



Family PTYCIIOPTERID.E. 



The immature stages of the genus Ptychoptera have 

 long been known to science; and I have now to add 

 some observations on the life history of the remarkable 

 and interesting Bittacomorpha clampes. Baron Osten- 

 Sacken's statement that the relationship of these genera 

 is "very great and evident, all the differences of the out- 

 ward appearance notwithstanding, " is abundantly con- 

 firmed by their immature stages, which are very much 

 alike in structure and appearance. 



The larvae [Fig. 15] live in shallow waters filled with 

 dead vegetable matter, leaves, or rushes. They are not 

 predaceous, and probably live on the minute growths 

 which would form in such situations. The head is well 

 developed, the body elongate-cylindrical, some of the 

 anterior abdominal segments bearing well-developed false 

 feet, and the posterior segments drawn out into a very 

 long partly retractile respiratory tube. In the pupa 

 [Fig. 19], on the contrary, one of the usual prothoracic 



