280 DIVISION II. ARTICULATED ANIMALS.—CLASS IV. INSECTA. 
of their burrow. When they have arrived at the surface, they cast off their 
burden, with a jerk, to a considerable distance. While lying in ambush for 
prey, the flat plate of the head just fits the mouth of the hole, forming a 
flat surface with the surface of the surrounding soil. They scize their 
victim with their jaws, and even rush upon it, precipitating it to the bottom 
of their burrows, with a see-saw motion of their head. They descend then 
with equal quickness at the least danger. They close the orifice of their 
dwelling when they change their skin, or undergo their change to the pupa 
state. 
Carabus. — Many of the species of this group are destitute of wings, 
and have only elytra. They often emit a fetid odor, and discharge an acrid 
and caustic liquid. The Carabici are very active insects, and live in the 
earth, under stones, or the bark of trees. Some of them secrete a very 
caustic fluid, which they discharge with an explosion. If the fluid falls 
upon the skin, it produces a stain like that made by nitric acid, and some- 
times a painful burn. Some species are social, and live in societies under 
stones. One species (C. sycophanta) is three fourths of an inch in length, 
of a velvet black, with the elytra golden-green, or brilliant copper, finely 
striated, each having three lines of fine, impressed dots. Its larva lives in 
the nests of the processionary caterpillars, upon which it feeds, devouring 
many in the course of aday. Other larve: of its own species, smaller and 
younger, attack and devour it when its voracity has overcome its activity. 
They are black, and are sometimes found running on the ground, or upon 
trees, especially the oak. 
A second family of the Coleoptera is represented by the genera Dytiscus 
and Gyrinus, and is called Hyprocantnari— the Swimmers. ‘Their feet 
are formed for swimming. They pass the first and last state of their exist- 
ence in fresh water. They swim well, and rise to the surface of the water, 
from time to time, to respire, ascending easily by holding their feet still, and 
suffering themselves to float. The body being turned upside down, they 
slightly elevate the tip of the body above the surface of the water, raising 
the extremity of the elytra, or bending down the abdomen, so that the air 
introduces itself into the spiracles, which they cover, and thence into the 
trachew. They are very voracious, and feed upon small animals, which 
ordinarily reside in the water, which the Hydrocanthari only leave during 
the night. They emit a very disagreeable odor. Sometimes they are at- 
tracted by light into the interior of houses. Their larve have a long, 
narrow body, composed of twelve segments, of which the first is the largest, 
with the head strong, and armed with two powerful mandibles. 
Dytiscus.— The larvew of this genus suspend themselves at the surface 
of the water by means of two appendages at the sides of the tail, which 
