thin and delicate on the dorsal aspect. It needs not now to be
resistant, because it is covered by the two firm forewings, which shield
and protect it, except when the insect is flying. There are, indeed,
slight changes in other structures not directly connected with the
wings. In a young grasshopper, for example, the feelers are relatively
stouter than in the adult, and the prothorax does not show the
specifically distinctive shape with its definite keels and furrows.
Changes in the secondary sexual characters may also be noticed. For
instance, in an immature cockroach both male and female carry a pair of
jointed tail-feelers or cercopods on the tenth abdominal segment, and a
pair of unjointed limbs or stylets on the ninth. In the adult stage,
both sexes possess cercopods, but the males only have stylets, those of
the female disappearing at the final moult.

Reviewing the main features of the life-story of a grasshopper or
cockroach, we notice that there is no marked or sudden change of form.
The newly-hatched insect resembles generally its parent, except that it
has no wings. Wing-rudiments appear, however, in an early instar as
visible outgrowths on the thoracic segments, and become larger after
each moult. All through its various stages the immature insect--_nymph_
as it is called--lives in the same kind of situations and on the same
kind of food as its parent, and it is all along active and lively,
undergoing no resting period like the pupal stage in the transformation
of the butterfly.

One interesting and suggestive fact remains to be mentioned. There are
grasshoppers and cockroaches in which the changes are even less than
those just sketched, because the wings remain, even in the adult, in a
rudimentary state (as for example in the female of the common kitchen
cockroach, _Blatta orientalis_, see fig. 4 _a_), or are never developed