
AQUATIC INSECTS OF FRESHWATER 

anterior legs are prehensile and adapted to aid in holding their prey. 
The many hundred eggs are deposited in a cocoon spun by the female 
and attached to the lower side of the floating leaves of aquatic plants or’ 
drifting leaves and branches, Fig. 226, to which the female clings with 
her posterior legs, and guards until the larve are hatched. These also 
somewhat resemble those of the Dytiscide but are thicker and have shorter 
mandables, those of the larger genera growing to 2% or 3 inches in 
length and % inch thick. They are popularly known as Spear- 
mouths, and are ravenous feeders, destroying water insects, flies, small 
snails, tadpoles, fishes, and their younger and weaker brethren; all of 
which they attack and 
crush with their power- 
ful madables to extract 
the “juices. ‘hey | are 
very destructive to young 
fishes and will destroy 
hundreds in a few days 
in the hatching and rear- 
ing tanks. The largest 
beetles of this family be- 
long to the genus Hydro- 
philus of which the most 
commonspeciesare /7. tri- 
angularis and H. glaber, 
Fig. 225, the next larger 
to Hydrocharis, of which 
FIG. 226, Water Scavenger-beetle or Great Water-beetle, Hydrophilus HH. obtusatus is the more 
glaber. Female attached to Egg-pouch and predaceous larva, or Spear-mouth. 

common, and the smaller 
to Hydrochus, of which about twelve species inhabit the Eastern and 
Middle States, the more common forms being H. scabratus and H.variolatus. 
There are a number of other genera, and some of the smaller species are 
not aquatic but live in moist earth and manure, feeding upon Dipterous 
larve. The Water-scavenger beetles are nocturnal in their flights, strong 
of wing and are attracted by lights and bright surfaces; are frequently seen 
near electric lights and will penetrate into houses, instances being recorded 
of their having found their way into household aquaria through open 
windows. All of this order have short antenne, clavate or clubbed at the 
tips and may easily be distinguished from the Diving-beetles. 
W arriicic-BeEeEt es, also popularly known as Scuttle Bugs and Spin- 
ners, belong to the family of Gyrinide and occur in great numbers on al- 
mostallstilland slow-flowing waters. They are brilliant bluish-black beetles 
270 
