nd marking may continue their
action almost unchecked.

It is perhaps in insects that we may best study the varied means by
which animals are defended or concealed. One of the uses of the
phosphorescence with which many insects are furnished, is probably to
frighten away their enemies; for Kirby and Spence state that a ground
beetle (Carabus) has been observed running round and round a luminous
centipede as if afraid to attack it. An immense number of insects have
stings, and some stingless ants of the genus Polyrachis are armed with
strong and sharp spines on the back, which must render them unpalatable
to many of the smaller insectivorous birds. Many beetles of the family
Curculionidae have the wing cases and other external parts so excessively
hard, that they cannot be pinned without first drilling a hole to
receive the pin, and it is probable that all such find a protection in
this excessive hardness. Great numbers of insects hide themselves among
the petals of flowers, or in the cracks of bark and timber; and finally,
extensive groups and even whole orders have a more or less powerful and
disgusting smell and taste, which they either possess permanently, or
can emit at pleasure. The attitudes of some insects may also protect
them, as the habit of turning up the tail by the harmless rove-beetles
(Staphylindidae) no doubt leads other animals besides children to the
belief that they can sting. The curious attitude assumed by sphinx
caterpillars is probably a safeguard, as well as the blood-red tentacles
which can suddenly be thrown out from the neck, by the caterpillars of
all the true swallow-tailed butterflies.

It is among the groups that possess some of these varied kinds of
protection in a high degree, that we find the greatest amount of
conspicuous colour, or at least the most complete absence of protective
imitation. The stinging Hymenoptera, wasps, bees, and hornets, are, as a
rule, very showy and brilliant insects, and there is not a single
instance recorded in which any one of them is coloured so as to resemble
a vegetable or inanimate substance. The Chrysididae, or golden wasps,
which do not sting, possess as a substitute the power of rolling
themselves up into a ball, which is almost as hard and polished as if
really made of metal,--and they are all adorned with the most gorgeous
colours. The whole order Hemiptera (comprising the bugs) emit a powerful
odour, and they present a very large proportion of gay