WATER-SCORPIONS. aT 
FAMILY NEPIDAE. 
(Water-scorpions ). 
This is another truly aquatic family of bugs, distinguished 
from all others by the presence of a long respiratory tube at the 
end .of the abdomen, as shown in the illustrations, Fig. 11 and 
Fig. 12. This tube is really composed of two half tubes through 
which the air is conveyed to the interior of the abdomen. Such 
atl apparatus enables the sluggish insect to obtain the necessary 
Fic. 11.—Nepa cinerea Linn.; a, adult; b, front leg, showing groove to receive rest 
of limb; c,egg. After Miall. 
supply of air by simply projecting it above the surface of the 
water, while it rests among water-plants near the bottom of the 
pond. As the water-scorpions are carnivorous, their front legs 
are fitted for seizing prey, while the others are fitted for walking, 
not swimming. The fore-tibie are curved, and carry a long, 
slightly bent, one-jointed tarsus. Both united fit into a chan- 
nel of the long and wide femora, like the blade of a pocket-knife. 
The head is narrow, and possesses rather prominent eyes. 
