16 A BOOK OF INSECTS 



second moult occurs about a month later, and a third one 

 at the end of the first year. This business of skin- 

 changing is gone through periodically by all growing 

 insects. It probably coincides with important physio- 

 logical processes, but men of science are still unable to 

 explain its full significance. We may discard, however, 

 the old theory that moulting is merely an aid to expan- 

 sion, for the sufficient reason that the soft parts of an 

 insect's skin can, if necessary, be stretched to an enormous 

 extent. An egg-laying queen of the so-called warlike 

 white ants, for example, may have an abdomen two 

 thousand times more bulky than the rest of her body, and 

 this amazing corpulency is attained without a single 

 moult. Again, certain Mexican ants are able to trans- 

 form themselves into temporary honey-pots. They con- 

 sume vast quantities of nectar until their bodies become 

 enormously distended, and then dole out the sweet food, 

 drop by drop, to hungry members of their community. 

 The ant's ability to perform this singular office is entirely 

 due to the elasticity of its skin between the hard abdo- 

 minal plates. Such feats indicate that periodic skin- 

 changing is not an indispensable accompaniment to 

 increasing bulk. 



There is still some doubt as to the exact time which 

 the young cockroach takes to reach maturity. It is 

 sometimes said that the insect does not become adult 

 until the fourth year of its life ; but w r hen one considers 

 how rapidly its numbers increase under favourable condi- 

 tions, one is inclined to doubt this statement. Perhaps 

 the period of infancy varies with the abundance or scarcity 

 of suitable food, or with the mean temperature of the 

 particular basement or store in which a clan of cock- 

 roaches has made its home. Be this as it may, the 

 important fact remains that the wings of the cockroach 



