As mentioned in "Butterflies of the British Isles," there is, speaking
generally, no clear line of division between moths and butterflies, and, as
Dr. Sharp, in "Insects," puts the case, "the only definition that can be
given of Heterocera [moths] is the practical one that all Lepidoptera that
are not butterflies are Heterocera." Now, it happens that all the
butterflies occurring in these islands have the tips of the horns
(_antennæ_) clubbed; and, although there is much variety in the structure
of the horns of our moths, none of them have the tips knobbed.
Like the butterflies, moths pass through the stages of egg, caterpillar,
and chrysalis before they attain the perfect state (_imago_), and the
duration of the several stages is just as variable. The majority assume the
moth condition but once in the year, but some species have two, or even
three, generations in the twelve months, whilst others occupy twenty-four
months in completing the life cycle. In one or two species the chrysalis
stage may last four, five, or even six years.
Diversity of form and structure is considerable in the early stages as well
as in the perfect insects, and this is shown in the {2} selection of
life-history details figured on the black and white plates in this volume.
[Illustration: FIG. 1.