
AQUATIC INSECTS OF FRESHWATER 

young fishes, weak flyers and clumsy of movement out of the water. In 
Mexico the eggs of two species, C. mercenaria and C. femorata, are 
collected in enormous quantities to be eaten by the Indians and are 
exported in a dried state as food for birds, poultry and fishes. They care 
distributed over the entire United States, the most general species being 
C. undulata, C. interupta, Fig. 196, C. calva, C. alternata and C. vulnerata. 
Back-swimMers belong to the family of Notonectide, of which 
about twelve species of the genera Notonecta, Anisops and Plea are known 
in the United States. Though greatly resembling the water-boatmen in 
appearance and habit they are 
more convex on the back, which is 
keeled like a boat and on which 
they swim with the ventral side 
upwards and the hind end of the 
body projecting to admit air beneath 
the wings where the breathing — 
apparatus is located. The anterior FG Lo Recerca, vine anand 
and middle legs are shorter than Ventral and dorsal views. Enlarged. 
the oarlike posterior legs, which are strongly developed for swimming. 
The eggs are laid in incisions, pierced by the ovipositor of the female in 
the stems of water plants. After hatching they rapidly pass through 
the larval stage and assume the appearance of the adult. They are 
predaceous and feed upon other water insects and small fishes, the power- 
ful beak inflicting severe wounds to the fingers in careless handling. 
They attack young fishes which are entirely devoured. The most gener- 
ally distributed species are N. undulata, Fig. 197, N. insulata, N. trrorata, 
A. platycnemis and P. striola. 
WarTeR-Scorpions belong to the family of Nepida and are so named 
from the appearance of the anterior legs, of which the coxa are long and 
the femor furnished with a groove into which the tibia and tarsus fits, 
greatly resembling the hooklike cheliceres of the scor- 
pion, and admirably fitted for seizing prey. The middle 
and posterior Jegs are adapted for walking. At the 
posterior end of the body two long half-tubes are de- 
veloped, which when united form a tube for inhaling air 
when under water. The species of Nepa are flat oval in 
form, about one inch long, and the Ranatra long, 
slender and twiglike, with all the legs thin and very 
long, the body oftenattaining a length of 21% to3 inches. 
The eggs are deposited in the stems of water plants 
and have long protruding filiments with probably pul- 


FIG, 198. Water-scorpion, 
Nepa apiculata. 
253 
