546 
sects in question are Halobates and Halobato- 
des... . They feed upon the floating bodies of 
dead marine animals, and may be seen to run 
out from such objects when alarmed by the ap- 
proach of a boat. These insects belong to the 
Rhynchota (Hemiptera) and in some respects 
come pretty near to such forms as Hydrometra 
or Velia.” Walker® has found once or twice 
several specimens of marine Hemiptera belong- 
ing to the group Halobates, gathered round 
floating pieces of seaweed, as if obtaining 
nutriment. However, it must be acknowl- 
edged, that practically nothing is known about 
the food of these creatures. McCook’ has 
demonstrated that individuals of Gerris remi- 
gis feed readily on the juice “ of finely ground 
boiled beef.” They take such food, with avid- 
ity, even in their own habitat. 
If a more critical study should be made of 
the food of aquatic bugs in general, in their 
various habitats, I believe that still further 
evidence would be accumulated, showing that 
considerable food, of the other kinds, besides 
insects, was used by these interesting forms. 
In fact Hungerford’ himself has pointed out 
a number of exceptions, some of which I can 
substantiate from my own observations, and 
to which I can add others also from my own 
observations. 
The following statements agree with those 
of Hungerford® to the extent that the aquatic 
bugs now to be mentioned, are not entirely 
predatory, nor is their food entirely that of in- 
sects: I have found by microscopic examina- 
tion of the alimentary system that water-boat- 
men of the genus Arctocorisa feed on vegetable 
matter; diatoms and Oscillatoria have been 
identified.. They probably obtain most of this 
from the ooze on the surface of the mud, at 
the bottom of the pond or stream. In order to 
obtain additional evidence, I placed some of 
5 Ibid., pp. 380-381. 
6““On the Genus Halobates Esch., and Other 
Marine Hemiptera,’’ Entomologist’s Monthly Mag- 
azine, Second Series, Vol. IV., p. 231, 1893. 
7“*‘Nature’s Craftsmen,’’ New York, 1907, pp. 
363-365. 
8 Loc. cit., pp. 336-337. 
9 Ibid. 
SCIENCE 
[N. 8. Vou. XLVIII. No. 1248 
the water-boatmen in shallow, glass dishes of 
water, with some of the ooze containing algal 
débris, as suggested by Hungerford,!® but my 
observations were discontinued before I was 
satisfied definitely that these bugs scooped up 
this substance with their front legs, and used it 
as food. I also placed back-swimmers of the 
genus Notonecta in shallow, glass dishes of 
water and fed them with small crustaceans, 
such as copepods and ostrocods. The back- 
swimmers appeared to thrive on this food. By 
means of a similar experiment, I was able to 
demonstrate that the marsh-treader, Hydrom- 
etra martini, will feed on copepods tangled in 
the surface-film. This was more likely to oc- 
cur when the water became somewhat stale. 
It is well known that many members of the 
family Gerridz, which consists of an assemb- 
lage of aquatic Hemiptera living on the water- 
film, feed mainly on terrestrial insects which 
fall into the water and float on its surface. 
Water-striders are considered to be entirely 
predatory in their manner of feeding, and so 
far as I know there is no statement to the con- 
trary in the literature on aquatic Hemiptera. 
However, it may be of interest to state that I 
have definite proof that Gerris remigis and 
Gerris marginatus both feed, at times, on veg- 
etable matter. The following statement is a 
modified extract, taken from my field notes: 
After having studied water-striders in their 
natural habitats for several months, especially 
with reference to their food relations, I de- 
cided that both Gerris remigis and Gerris mar- 
ginatus were entirely flesh-eating. However, 
on October 14, 1911, this opinion was changed. 
At the time, I was making observations of the 
water-striders on the surface-film of a brook 
near Whiteheath, which is approximately 
eighteen miles southwest of Urbana. Small 
red fruits were observed, drifting downstream, 
and these attracted the attention of the water- 
striders at once. Both species seized them 
readily, Gerris remigis with the greater avid- 
ity, and pushed their beak-like mouth-parts 
through the outer skin, down into the inner 
fruit. Some of the fruits, with their attendant 
water-striders, drifted near the bank of the 
10 Loe. cit., p. 337. 
