With something in the region of a quarter of a million
species, the beetles are by far the largest group of insects. Rather
more than 4,000 species are known in the British Isles but, although
many of them turn up in the garden from time to time, very few are in
any way restricted to garden habitats.
Beetles are generally recognised very easily because
the front wings are hardened and modified into protective shells called
"elytra". These elytra usually cover the whole abdomen, but
they are very short in "Rove Beetles" and they are absent
altogether from the female "Glow-worm". Only the hind wings
are used for flight, but most beetles prefer to keep their feet firmly
on the ground or on the vegetation and they don't very often fly. They
scuttle away when disturbed, or else they just drop to the ground and
play possum (lie still), with their legs held tightly against the body.
Many beetles have no hind wings at all, and their elytra are fused together
and immovable. It is possible that some of the beetles will be confused
with the "Heteropteran bugs" to start with, but the elytra
of the beetles always meet and form an obvious junction in the mid-line,
whereas those of the bugs always overlap. In addition, the beetles all
have biting jaws and never have the piercing beak which is so obvious
in the bugs.
Beetles can be found almost anywhere, for their tough
elytra give them added protection and allow them to occupy places which
are denied to other winged insects. Many of them, for example, live
in the soil and under stones, while others spend their lives groping
their way through piles of stored grain and flour. Water beetles use
the spaces between their elytra and their bodies as rechargeable air
cylinders which enable them to spend long periods under the water. Associated
with their wide range of habitats, the beetles also make use of a very
wide range of foods, both animal and vegetable, living and dead. Many
have a remarkable metabolism which enables them to survive without free
water, and it is this ability which has led to the establishment of
grain weevils, carpet beetles, and other species as pests in food stores
and domestic premises. In general, the larvae of the beetles eat much
the same kind of food as the adults, and both stages therefore cause
damage. The larvae themselves are very variable, ranging from the very
active young of the ground beetles to the legless grubs of the weevils.
Most of the plant-feeding beetle larvae are rather stout and slow moving,
bearing three pairs of legs at the front of the soft and often brightly
coloured bodies.
One group of beetles stand apart from the others which
are found in the garden and which can be found indoors. This group is
known as the Ground Beetles. These beetles are fast moving and very
predatory. They have long legs and a characteristic angular shape. They
also bear fine sensory bristles on various parts of the body, but these
are not easily seen without a lens or at least close examination. Many
ground beetles have a beautiful metallic sheen when seen from certain
angles, but the majority are of a sombre hue and generally look black
when seen in the garden. The best way to see ground beetles is to go
out with a torch at night, they can be seen hunting slugs
and other tasty morsels.
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