146 Annals Entomological Society of America [Vol. VII, 
habit resembles a similar one described by Fulton (’11, p. 300) 
for certain Diptera, the adults of which also congregate in the 
flowers of a yellow waterlily. Later when the anthers became 
‘spread out the flies found better concealment beneath them. 
The conspicuous assembling of flies in the flowers is indic- 
ative of some rather strong attraction which the latter have for 
the former and it seems safe to assume that the flies profit 
therefrom. Nectar is said (Lovell, ’02, p. 205) (Robertson, 
’89, p. 122) to be secreted on the outer faces of the petals in 
Nymphaea advena and it is also probably true of Nymphaea 
americana. Therefore it is possible that the visits of the 
flies are induced in part by the presence of nectar which forms 
a source of food supply. Flies were observed in the flowers 
from the time of opening to the time when the flowering parts 
began to disappear. 
(2). Possible agents in pollination.—The information that 
insects are found in connection with yellow waterlilies is not 
new since species representing several orders have been reported 
as occurring on these plants by Robertson (’89, pp. 122-123), 
Lovell (98, pp. 60-65), Bembower (11, p. 379) and others. 
Furthermore Elliot ('96, pp. 117-118) and others claim that 
flower haunting Dzptera are of considerable importance in the 
fertilization of many of the flowers which are visited. It 
is claimed that N. advena may be self- or cross-pollinated 
(Bembower, ’11, p. 379) and this is probably true also of JN. 
americana. There is good evidence in support of the view that 
the insect visitors of yellow waterlilies (V. advena and others) 
may transfer pollen from one flower to another, or from one 
part to another on the same flower. The writer had occasion 
to examine large numbers of the adults of Hydromyza confluens 
and it was discovered that many were carrying the pollen of 
N. americana. Swarms of adults taken’from flowers in which 
they had congregated showed that the great majority, and 
often all, of the insects were dusted with pollen. Very fre- 
quently pollen occurred so thickly over the body that the 
insect was distinctly yellow in appearance. Adults collected 
August 5-22, showed that pollen was being carried during this 
entire period. While it was not demonstrated absolutely 
that these flies carry pollen from one plant to another, the 
circumstantial evidence seems to point definitely to these insects 
as being at least one of the factors in the cross-pollination 
