136 Annals Entomological Society of America  [Vol. VII, 
advena variegata, but Miller and Standley ('12, p. 78), have 
shown that the boreal species has several distinct characters 
which separate it from the true advena, and they have raised 
Provancher’s name, americana, to indicate this northern 
species. N. americana occurs in some abundance in the protected 
bays, in the beach pools, in the mouths of some of the streams, 
and in sphagnum bogs of the Douglas Lake region and the 
insects under consideration were correspondingly abundant. 
Needham (’08, p 270), reported this insect in connection with 
Nymphaea advena, but judging from his description and figures 
it seems very probable that the species in Walnut Lake was 
N. americana, rather than the true advena. 
A careful examination of all the aquatic plants occurring 
in the immediate vicinity of the Nymphaea beds was made 
with the view of determining whether or not other plants were 
used as food. In no case did the larva occur on plants other 
than N. americana. The white waterlilies (Castalia odorata) 
were entirely exempt in spite of the fact that white and yellow 
waterlilies mingled in the same beds. In every case the evi- 
dence pointed to the conclusion that this insect is restricted to 
N. americana in the region studied. 
The Gall.—The immature stages of this.insect were found 
in the long, constantly submerged petioles of the yellow water- 
lily. A large number of plants were examined and in no case 
did they occur on any part of the plant other than the petiole. 
Furthermore they were confined exclusively to certain petioles, 
namely, those of the floating leaves. Special effort was made 
to determine whether or not larve ever occurred on the 
peduncles or on the petioles of the submerged leaves. Both 
were found to be entirely free from infestation. Although 
the writer has no data on the method of oviposition, the reason 
for this distribution on the plant seems apparent. Needham (’08, 
p. 270) suggested that ‘‘ Probably the attack of the gall maker 
begins when the first leaves reach the surface in late spring; 
then they have their first opportunity to reach the proper 
place of oviposition by crawling down the stalk.’”’ The writer 
regards this as the most feasible explanation since it will be 
shown later in this paper that it is possible for the adult insect 
to pass under water by crawling on a supporting surface and 
that it actually does so of its own volition. The short and 
wholly submerged leaves of N. americana do not at any time 
