Order
- COLEOPTERA (Greek,
koleos = sheath; pteron = wing)
Common
Names:
beetles, weevils, ladybirds
Distribution:
Cosmopolitan
Suborders:
Adephaga, Polyphaga
Description
Beetles usually have a strongly stiffened (sclerotised) exoskeleton and
frequently possess well developed mandibles. The compound eyes are varied
in structure and development but simple eyes (ocelli) are usually absent.
Antennae are varied in structure and development. The forewings (those
nearest the head) are modified to form hard, protective covers (elytra)
for the hind wings. Hind wings are membranous and used for flying. Beetle
flight is usually very distinctive with the wing covers (elytra) held
stiffly out from the body.
Larva
Coleoptera
Video
A ladybird beetle feeding on aphids
Larvae
are often referred to as "grubs" and usually have 6 legs on
the thorax. The larvae always have a hard chitinised head capsule with
antennae and mandibles. Pupae have mandibles, but these are immobile.
Other pupal appendages (e.g. legs, wings, antennae) may be free or fixed
depending upon the species.
Members
Beetles - scarabs, click beetles, water beetles, borers of many kinds,
dung beetles, all weevils, fireflies, ladybirds, longicorn beetles, Christmas
beetles, etc.
Food
Almost every vegetative source has been exploited by a beetle species
including flowers, buds, stems, roots, seeds, bark, wood, galls, leaf
or forest litter, etc. Dung, fungi and carrion are used by many species.
Very few species are parasitic but many are carnivores. Some beetles attack
preserved animal products such as hides or leather. The order has been
extremely successful in colonising almost every possible habitat.
Importance
Beetles are of extreme importance in the forestry, timber and gardening
industries. Enormous damage is done to wood products by boring beetles.
Grub stages attack the roots of grass or other plants causing considerable
damage. In Europe, the ambrosia beetle acts as a vector of the fungal
parasite that causes Dutch elm disease. This disease has destroyed enormous
numbers of elm trees all over the European continent. Annually weevils
destroy millions of dollars worth of grain or grain products on a world
basis. Beetles have been useful for their application as biological control
agents: dung beetles assist with the disposal of horse and cattle manure;
the weevil (Cyrtobagus sp.) is used to control Salvinia
in Australia and Papua New Guinea. Adults and larvae also play an important
role in the re-cycling of dead and decaying timber. The organic farming
industry encourages beetles such as ladybirds for predation on
aphids and similar destructive insects.