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The
Diversity of The World of Life
True
Insects (Insecta)
Beetles,
Including Weevils
& Grubs
(Coleoptera)
Representatives
Beetles,
including Weevils
Grubs
Biology
APPROXIMATE NUMBER OF KNOWN SPECIES WORLDWIDE
300,000 -- there are over 70 times as many known species
of beetles as there are of all mammals put together! Beetles are
probably the largest single order of
all insects and, in terms of the number of individuals, the most common
insects in the world.
DESCRIPTION
Beetles are small to large.
The mouthparts are chewing.
There are usually two pairs
of wings. The veinless,
somewhat hard or leathery forewings do not overlap one another -- they
meet in a straight line down the middle of the back -- but they do cover
the membranous, larger hindwings, folded underneath when not in use.
At rest, the wings of most, but not all, beetles cover almost all the
abdomen.
"Weevils" are a family of beetles that have clubbed, almost
always elbowed antennae and a long, characteristic snout.
METAMORPHOSIS
Unsurprisingly, given the diversity of beetle species,
there are many different types of beetle larvae -- including
"grubs", with a distinct head and well-developed legs, and
"wireworms", with
less developed head and legs -- and different types of beetle pupae.
The larva
of a weevil looks like the maggot of a
fly, although its head is distinct.
HABITATS
Beetle larvae and adults are found almost everywhere on
land that animals can live; and some are even found in saltwater marshes
and freshwater lakes and streams.
FOODS
Many beetle larvae and adults scavenge for debris, many
feed on all sorts of plant parts, some feed on products derived from
plants or animals, many prey on other insects, and a few parasitize larger
animals (as in nests).
DAMAGES/BENEFITS
Many beetles (such as most dung beetles and some rove beetles and white grubs)
are valuable decomposers of natural litter, such as the dung or carcasses of
large animals.
A few beetles pollinate flowering plants -- sometimes
crops, sometimes weeds.
Many beetles feed on crops and other valuable plants, which
are sometimes infected by diseases in the process. White grubs often feed on the roots of grasses; many
adult scarab beetles feed on the leaves of trees; wireworms feed on seeds
and roots; the larvae of longhorned beetles bore through the wood of
trees; and
the larvae and adults of the boll weevil destroy cotton crops worth millions of
dollars every year.
A few beetles (such as the Klamathweed beetle, imported into northern
California) feed
only on weeds.
Some beetles (such as the larvae and adults of dermestid
beetles) feed on all sorts of stored foods and other household goods
(Entomologists put moth balls in their insect collections to ward off such
pests).
Some beetles (such as the larvae and adults of most ground
beetles) feed on many other insects, often crop pests. Lady beetles
are gathered from their hibernation quarters, as in the foothills of
California, and sold as "biological controls".
Finally, blister beetles put-out a poisonous chemical; and
the bite of large insects in general can be very painful to us human
beings.
True
Insects (Insecta)
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