ArticTvE IV. — Notes on North American Diptera, with Descrip- 

 tions of Nezv Species in the Collection of the Illinois State Laboratory 

 of Natural History. By J. R. M alloc h. 



In the course of my work of identifying and arranging the Diptera 

 in the collection of the State Laboratory of Natural History I have 

 found several which belong to apparently undescribed species. I have 

 in many cases given to these forms manuscript names, and as certain 

 of the species may figure in the publications of the Laboratory, or 

 in those of the State Entomologist, it is deemed advisable to publish 

 descriptions of these species so as to validate the names under which 

 they stand in the collection. 



The types of the new species herein described are all in the collec- 

 tion of the Illinois State Laboratory of Natural History. 



During the progress of work in connection with the Biological 

 Survey of the Illinois River many species of Diptera have been taken 

 either as larvae, pupae, or imagines, and several of these species 

 belonging to the family CJiironomidce are dealt with in this paper. 

 The largest species of the genus Chirononius known from this country 

 is represented by a great amount of material including all stages, and 

 as no other chironomid has been recorded as having so large a larva 

 as this form, and particularly because the species has not been 

 described in this stage, this opportunity is taken to describe it. That 

 these larvae form a very considerable proportion of the food of river 

 fishes is well known, and the presence of such species as Chirononius 

 fcrrugincovittatus Zetterstedt, here referred to, no doubt enhances 

 the status of the river as a fish-producing stream. 



CHIRONOMID^ 



Chironomus compds Coquillett 



Chironomus compcs Coquillett, Proc. Ent. Soc. Wash., Vol. IX, 1908, p. 145. 



Female. — Face and frons brownish yellow; antennae yellow, 

 becoming brown towards apex; palpi brown. Mesonotum pale 

 yellowish brown; viewed from behind the usual three vittae are dark 

 reddish brown, the spaces between them, and also posterior to the 

 short central vitta, are distinctly white pollinose ; scutellum yellowish ; 

 pleurae pale brown, the surfaces with white pollinosity. Abdomen 

 brown, the posterior margin of all the segments with a broad white 

 pollinose fascia. Legs whitish yellow, fore femora brown, with a 

 pale band just before apices ; all tibiie with the bases broadly and the 



