312 ILLINOIS ACADEMY OF SCIENCE 



afternoon and evening. The other species whose meth- 

 ods of feeding are known have habits that are very simi- 

 lar to the above. The eggs are deposited in moist situ- 

 ations such as the one described above. 



The most striking feature of the life-history is its ex- 

 treme brevity. This duration was determined in the 

 following mamier : In 1917, the Floriculture department 

 of the University of Illinois laid out a portion of the 

 grounds on the south campus as a garden and devoted 

 a small part to flowers found in rocky situations. In 

 this part they installed a bubbling fountain among some 

 rocks at one side of the winding, declivitous walk, the 

 water flowing from the fountain being conducted to the 

 sewer some distance away by means of an open gutter 

 along one side of the walk. This gutter had become ob- 

 structed by vegetable growth and while examining an 

 artificial pond near the garden for mosquitoes, the small 

 pools in the gutter were also examined to discover if any 

 mosquito larvae were present. No mosquito larvae were 

 found but among the aquatic insects along the gutter 

 were some interesting forms, including an Anthomyiid, 

 Lispa tentaculata (De Geer), some species of Dolicho- 

 podidae, about three species of Chironomidae, and lar- 

 vae, pupae and imagines of Geranomyia canadensis. The 

 larvae and pupae of the last named species were found 

 on the surfaces of the rocks over which the water from 

 the fountain flowed very swiftly, some on the vertical 

 portions, and were remarkably conspicuous owing to the 

 fact that the surfaces on which they lay were coated 

 with a rusty colored diatomaceous deposit from the 

 water, which is of artesian origin. 



Several of the larvae were removed to jars and kept 

 alive for over a week but failed to pupate. Adults were 

 found commonly alongside the gutter, resting on the 

 vegetation, feeding on the nectar of flowers or in copu- 

 lation. In 1919, this bubbler in the Eock Gardens was 

 turned on for the season on April 25. On May 24, the 

 rock surface was thickly covered with diatomaceous ooze 

 but no larvae could be found and, if present, must have 

 been very small. On June 28, just five weeks later, half- 



