[17]
_The Variability of Insects_.
Among Insects there is a large amount of variation, though very few
entomologists devote themselves to its investigation. Our first examples
will be taken from the late Mr. T. Vernon Wollaston's book, _On the
Variation of Species_, and they must be considered as indications of
very widespread though little noticed phenomena. He speaks of the
curious little carabideous beetles of the genus Notiophilus as being
"extremely unstable both in their sculpture and hue;" of the common
Calathus mollis as having "the hind wings at one time ample, at another
rudimentary, and at a third nearly obsolete;" and of the same
irregularity as to the wings being characteristic of many Orthoptera and
of the Homopterous Fulgoridae. Mr. Westwood in his _Modern
Classification of Insects_ states that "the species of Gerris,
Hydrometra, and Velia are mostly found perfectly apterous, though
occasionally with full-sized wings."
It is, however, among the Lepidoptera (butterflies and moths) that the
most numerous cases of variation have been observed, and every good
collection of these insects affords striking examples.
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