Entomology of the Illinois River. 211 



were found in diminished numbers in late July and 

 August, while pupae occurred in August and September. 

 The imagos became common early in May and con- 

 tinued so for several \A'eeks. None were seen later until 

 copulating imagos were noted at Matanzas Lake Aug. 

 24. Others were occasionally observed afterward, speci- 

 mens being taken Aug. 30 and Sept. 15. The same 

 interval occurs in our general collections, the imago 

 haviDg been taken five times between May 1 and 23, 

 five times between July 18 and August 16, once on 

 Sept. 19, but not at any other time in Illinois. We 

 have examples from New Orleans, La., collected April 

 23. Our other material is all from Peoria, McLean, and 

 Champaign counties. The above data would indicate 

 that the species is two-brooded, hibernating as a larva 

 and emerging early in May, the second brood maturing 

 in late summer and early fall. 



That the larva is by no means limited to a riparian 

 range was shown by the occasional finding of a larva 

 or pupa in the extensive areas of shallow water at the 

 head of Quiver Lake, one being taken with a dip-net 

 from the bottom where the water was entirely free from 

 standiDg or floating vegetation. The long fleshy anal 

 appendages are doubtless analogous to the posterior 

 filamentg of many Chironomus larvae, assisting in the 

 aeration of the blood. The movement of the body- 

 contents of the larva in crawling alternately relaxes 

 and dilates these appendages and as they project ob- 

 li(|uely backward they help in locomotion. The imago 

 flies by night, and is one of the species attracted to 

 lights, where much of our material has been obtained. 



