1917] Studies on Hydromyza Confluens Loew 41 



THE ADULT 



In the writer's earlier paper ('14), a number of observations 

 on the habits and activities of the adults were presented, and 

 subsequent studies have yielded data which are confirmatory of 

 the same. In addition, a few new data were secured which 

 seem worthy of record. 



Food Habits. — The relation of these flies to the yellow water- 

 lily has been discussed somewhat in detail in the above-men- 

 tioned paper (pp. 145-147) and the possibility of nectar being pro- 

 duced by the flowers of A^". americana and serving as a food for 

 these insects was pointed out. This matter is still in doubt but 

 the behavior of the flies in the flowers offers circumstantial 

 evidence in favor of such a conclusion. However, it appears 

 that the flies have other means of solving the food problem. 

 Adults were repeatedly observed feeding on the exposed tips 

 of the stamens. In most cases, this behavior was too long 

 continued to be interpreted as a mere random inspection or 

 testing of the stamen surface. The character of the food secured 

 from the tips of stamens is not known. Possibly the pollen 

 serves as food. Occasionally, flower stalks were, by different 

 mechanical agents, broken off above water and partly stripped 

 down, exposing a broken end on which an exudation of the 

 liquid substances of the plant occurred. Flies often gathered in 

 considerable numbers on such broken stalks and fed there for 

 long intervals. 



It also appears that these flies do not confine their feeding 

 activities wholly to the yellow water-lily. Occasionally, adults 

 of Chironomus sp. were found dead on the water-lily leaves and 

 many of them, in the process of rapid disintegration, were dis- 

 covered by these flies, the latter clustering about the dead 

 insects and performing feeding movements. The evidence 

 seemed conclusive that the flies were feeding on the juices of the 

 dead insect. A number of experiments were tried by securing 

 the bodies of Chironomus sp. and, after allowing them to lie in 

 water for several hours, they were placed on the water-lily 

 leaves where the adults of H. confluens were abundant. It was 

 shown in this way that the dead insects had a distinct attraction 

 for the flies, the latter seeking them rather quickly and def- 

 initely when not too remote from them. This response was so 

 definite that the writer used the dead insects as a trap for the 

 flies, thtis facilitating the collection of the latter. 



