THE SEXES OP INSECTS. 
9 
in ti eating oi the development of insects it is necessary to refer to the 
periodical casting of the larval skin. All the growth of insects takes 
place in the larva state. Consequently no insect increases in size after 
it has acquired wings. The larval skin seems to be an imperfectly or- 
ganized membrane, which does not -correspond in its growth to that of 
the body, but yields to this growth, to a certain extent, by virtue of its 
elasticity. A time comes therefore when it can yield no farther. The 
insect then evidently becomes oppressed, ceases to eat, usually retires 
to some secluded spot, and, if gregarious, huddles together with its com- 
panions, and there remains a day or two, almost motionless and with- 
out food, and in an apparently torpid and sickly condition. After a 
time the distended skin bursts open, and the insect throws it off, and ap- 
pears in a new, bright, and elastic skin, which, in its turn, is capable of 
a certain degree of distension. This process, which is called moulting, 
takes place three or four times in the course of the larval growth, and 
in a few larvae which continue more than one year in this state, the moul- 
ting is said to occur from live to eight times. In insects of very rapid de- 
velopment, on the other hand, such as the maggots, or larvae of the 
Muscidae, no moulting takes place, and it is the larvae of this kind which 
form coarctate pupae. 
THE SEXES OP INSECTS. 
As a general rule insects of different sexes resemble each other so 
closely as to leave no doubt of their specific identity, and in many the 
sexes can scarcely be distinguished. But this rule is subject to many 
exceptions, and the naming of insects has been greatly confused by the 
sexes of the same insect having been described and named as distinct 
species. 
The sexual organs, especially those of the males, are usually conceal- 
ed so as to be nearly or quite invisible; but the female, especially in 
the order of Hymenoptera, often have an exserted ovipositor of greater 
01 less length, which readily distinguishes them from the opposite sex. 
An analogous structure exists in many wood-boring beetles which de- 
posit their eggs in deep crevices in the bark of trees ; and more rarely 
in insects ot the other orders. In the Coleoptora the males are sometimes 
distinguished by one or two horns, either upon the head or thorax, and 
many of the predaceous beetles, both terrestrial and aquatic, have the 
anterior feet much widened, and furnished beneath with a cushion of 
hairs or bristles. 
The antennae usually differ in length but little, if at all, in the two 
sexes ; but in the long-homed beetles (Oerambyehhc) the antennae of the 
males are generally considerably longer than those of the females. 
—2 
