the sides of the abdomen, the head constricted behind the
eyes to form a neck, and the claws of the feet divided to the base.
Several of the _Meloidae_ (such as the "Spanish fly," fig. 24) are of
economic importance, as they contain a vesicant substance used for
raising medicinal blisters on the human skin. The wonderful
transformations of these insects were first investigated by G. Newport
in 1851, and have recently been more fully studied by C. V. Riley
(1878) and J. H. Fabre. The first larval stage is the "triungulin," a
tiny, active, armoured larva with long legs (each foot with three
claws) and cercopods. In the European species of _Sitaris_ and _Meloe_
these little larvae have the instinct of clinging to any hairy object.
All that do not happen to attach themselves to a bee of the genus
_Anthophora_ perish, but those that succeed in reaching the right host
are carried to the nest, and as the bee lays an egg in the cell the
triungulin slips off her body on to the egg, which floats on the
surface of the honey. After eating the contents of the egg, the larva
moults and becomes a fleshy grub with short legs and with paired
spiracles close to the dorsal region, so that, as it floats in and
devours the honey, it obtains a supply of air. After a resting
(pseudo-pupal) stage and another larval stage, the pupa is developed.
In the American EPICAUTA VITTATA the larva is parasitic on the eggs
and egg-cases of a locust. The triungulin searches for the eggs, and,
after a moult, becomes changed into a soft-skinned tapering larva.
This is followed by a resting (pseudo-pupal) stage, and this by two
successive larval stages like the grub of a chafer. The
RHIPIDOPHORIDAE are beetles with, short elytra, the feelers pectinate
in the males and serrate in the females. The life-history of
_Metoecus_ has been studied by T. A. Chapman, who finds that the eggs
are laid in old wood, and that the triungulin seeks to attach itself
to a social wasp, who carries it to her nest. There it feeds first as
an internal parasite of the wasp-grub, then bores its way out, moults
and devours the wasp larva from outside. The wasps are said to leave
the larval or pupal _Metoecus_ unmolested, but they are hostile to the
developed beetles, which hasten to leave the nest as soon as possible.

STREPSIPTERA.--Much difference of opinion has prevailed with regard to
the curious, tiny, parasitic