
AQUATIC INSECTS OF FRESHWATER 

ed in the water and the larve leave the water, burrow into the ground to 
there undergo the final metamorphosis. The flight of the Diving-beetles 
is nocturnaland their specs 

migrations are from 
pond to pond, being 
also attracted by 
bright surfaces and 
lights. The com- 

mon genusis Acilius 
which is about 34 FIG. 223. Predaceous Diving-beetle, Acilius fraternus, Female and male, Enlarged, 
inch long, of a polished brownish-black color, marked with dull yellow; 
the elytra covered with fine punctures, the female having four furrows 
oneach wing cover. ‘The morecommon species are 4. fraternus, Fig. 223, 
and 4. mediatus. ‘The largest belong to the Dytiscus, Cybister and allied 
genera; the former having the cups on the under side of the tarsal discs 
varying in size, and 
the latter similarand 
of uniform size. 
The more common 
of these are D. fas- 
civentris, Fig. 224, 
D. hybridus, and 
C. fmbriolatus. Vhe 
genus Colymbetes 
has the elytra mark- 

FIG. 224. Predaceous Diving-beetle, Dydiscus fasciventris. Female and male. ed with apis chon 
Enlarged. — fine transverse stria- 
tions. The most common species is C. scu/ptilis. 
All are fairly good flyers and widely distributed 
in almost the entire United States, 
W aTER-SCAVENGER BEETLES (GREAT WATER- 
Beetes) belong to the family of Hydrophilide 
and closely resemble the Predaceous Diving- 
beetles in general appearance, but are more 
convex and have short club-shaped antennz 
concealed beneath the head and very long 
palpi, the parts next to the mandables. They 
are dusky-black beetles of elong-elliptical 

form, strong, active and of savage disposition. 
Both the middle and the posterior legs are fringed FIG. 225. Water Scavenger-beetle 
: . = 5 = - or Great Water-beetle, Hydrophilus 
with hairs and adapted for swimming; while the palo (Male 
269 
