124 CRABS AND INSECTS. 
nal female may be represented in the twelfth generation 
by one quintillion descendants, all born in a single sum- 
mer. Upon the approach of cold weather, or from a lack 
of food, males and females are pro- 
No duced by the viviparous form, and 
eggs are laid that in the spring give 
rise to successive broods, as above. 
Order V. Beetles (Coleoptera). 
—General Characteristics.—Insects 
having their fore-wings thickened, 
forming horny sheaths, called era, 
or wing-covers for the hinder pair, 
that are principally used in flight; 
mouth-parts adapted for biting ; 
metamorphosis complete. 
The Girdler (Oxcideres),—This 
Fic. 152.—Aphis. beetle displays remarkable intelli- 
gence in providing for its young. 
The eggs are deposited in perforations in the tender 
brushes of hickory, and, as the young require dead wood 
to eat, the mother girdles the limb below the eggs with 
her mandibles, so that it dies by the time the larva 
hatches. : 
Spring-Beetles (Z/ateridz).—These beetles are light- 
givers (Fig. 153), and when placed upon their backs have 
the power of spring- 
ing repeatedly into 
the air by using a 
spine situated be- 
tween thelegs. The 
larvee are known as 
wire-worms, and feed 
upon vegetable mat- Fic. 153.—A luminous beetle (Pyrophorus 
ter, sometimes re- noctilucus), 
maining five years 
in the larval state. The yellow luminous spots are upon 
