both sexes have imperfect, crumpled wings, and are incapable of flight;
but still there is a trace of the characteristic difference in the two
sexes; for though, on comparing a number of males and-females, I could
detect no difference in the development of their wings, yet I was
assured by Mrs. Whitby that the males of the moths bred by her used
their wings more than the females, and could flutter downwards, though
never upwards. She also states that, when the females first emerge from
the cocoon, their wings are less expanded than those of the male. The
degree of imperfection, however, in the wings varies much in different
races and under different circumstances; M. Quatrefages[511] says that
he has seen a number of moths with their wings reduced to a third,
fourth, or tenth part of their normal dimensions, and even to mere
short straight stumps: "il me semble qu'il y a la un veritable arret de
developpement partiel." On the other hand, he describes the female
moths of the Andre Jean breed as having "leurs ailes larges et etalees.
Un seul presente quelques courbures irregulieres et des plis anomaux."
As moths and butterflies of all kinds reared from wild caterpillars
under confinement often have crippled wings, the same cause, whatever
it may be, has probably acted on {304} silk-moths, but the disuse of
their wings during so many generations has, it may be suspected,
likewise come into play.

The moths of many breeds fail to glue their eggs to the surface on
which they are laid,[512] but this proceeds, according to Capt.
Hutton,[513] merely from the glands of the ovipositor being weakened.

As with other long-domesticated animals, the instincts of the silk-moth
have suffered. The caterpillars, when placed on a mulberry-tree, often
commit the strange mistake of devouring the base of the leaf on which
they are feeding, and consequently fall down; but they are capable,
according to M. Robinet,[514] of again crawling up the trunk. Even this
capacity sometimes fails, for M. Martins[515] placed some caterpillars
on a tree, and those which fell were not able to remount and perished
of hunger; they were even incapable of passing from leaf to leaf.

Some of the modifications which the silk-moth has undergone stand in
correlation with each other. Thus the eggs of the moths which produce
white