1914] Life History of Hydromyza Confluens, 145 
surface if opportunity affords. They stay below only by 
clinging to some submerged object. While under water a 
goodly supply of air clings to them in the form of a dense, 
silvery coating. When allowed to come to the surface they 
immediately lose the silvery coating and are apparently as 
dry as if they had never been in contact with water. Experi- 
ments, in which adults were subjected to forced submergence 
for varying lengths of time, showed that they can remain 
under water for several minutes without apparent detriment 
to themselves, due without doubt to the generous coating of 
air which surrounds them. Submerged individuals usually 
appeared uneasy and made vigorous effort as if seeking release. 
The ease with which they apparently resist wetting and the 
quantity of air which they take below with them make possible 
the mode of emergence and oviposition suggested above. 
Relation to the Yellow Waterlily.—The adults as well as the 
immature stages have a definite and interesting relation to 
the yellow waterlilies. This relation will be discussed under 
two heads, (1) food relation, and (2) possible agents in pollina- 
tion. Although each of these relations will be treated inde- 
pendently, it will be understood that such separation is purely 
artificial and also that both are operative at the same time. 
(1). Food relation.—The time of maximum abundance of 
the adults coincided closely with the opening of the majority 
of the flowers and it was very evident that the flies were deriving 
food products from them. Flies swarmed in the newly opened 
flowers in great numbers, congregating between the petals and 
the stamens to the extent that often the interior of the flower 
was black with them. In the case of flowers which had been 
open only a short time the anthers were crowded in a compact 
mass under the edge of the expanded stigma or were just 
beginning to spread out in a radial fashion, while the petals 
had spread out widely, thus forming a cup-shaped flower 
and producing a space between the petals and anthers into 
which the flies crowded. Flowers frequently contained as 
many as fifty adults. They regularly disposed themselves as 
described above with the heads in close proximity to the base 
of the anthers. It often required a distinct shake of the 
flower stalk to disturb them and this proved to be an easy 
way to collect adults since one of these flowers could be cau- 
tiously thrust into a bottle and the inmates dislodged. This 
