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Beetles,
order Coleoptera, is the largest and most diverse order of insects. Their
size is ranges from 0.5mm to 200mm. J.B.S. Haldane's famous comment on
beetles has been quoted many times. During a lecture on the biological
aspects of space flight given in 1951. Haldane remarked that "the
Creator, if He exists, has a special preference for beetles, and so we
might be more likely to meet them than any other type of animal on a
planet that would support life". We have the discussions on why
insects, especially beetles, are so success in here.
Coleoptera
means ‘sclerotised wings’. All beetles have hard forewings, called
elytra, which do not do much help in flying but cover the membranous hind
wings and protect the abdomen. Some beetles cannot fly but some others can
fly very fast. When flying the hind wings extended to the fright position.
The forewings, or elytra, are lift up vertically or in side way, which is
believed will have the aerodynamic effect on the fright. When at rest, the
elytra meet edge to edge in a straight line at the centre over the
abdomen. The hind wings are neatly folded under the elytra.
The
beetles are usually bright in colour. They are complete metamorphosis. The
adults are usually feed on nectar and pollen. Some are feed on plants
leave. Larva may be found underground or under the bark of living trees.
Classification :
There
are more than a hundred families of beetles in Australia. We listed
here with the most common species and those easily found in Brisbane. We
will gradually add the species and family lists, with more pictures and
information. Please come back and check our web site from time to time.
 Family
CANTHARIDAE - Soldier Beetles
- Beetles in this family
are usually small in size, brown and yellow in colour. Adults bodies
are soft, flat and long. Their antenna are filiform. They are abundant
on flowers and foliage where they feed on nectar, pollen, or other
insects. Larvae of most species are carnivorous, a few species feed on
plants.
-
 Family
CERAMBYCIDAE - Longicorn Beetles
All members in this family commonly call Longicorn Beetle. They have
very long antennae, more than two-thirds, some are even three times as
their body length. Their antenna can directed backwards over their
body, typically 11 segmented. Their compound eyes are notched at the
base of the antennae.
-
 Family
CHRYSOMELIDAE - Leaf Beetles
This family is commonly called Leaf Beetle. Most species of this
family feed on leaves. Leaf beetles adults usually range in size
from 5 to 15 mm in length and are brightly coloured. They have
different body shapes from elongate or flattened to globular. Some may
be mistaken for ladybird beetles due to their oval shape. Their
antenna usually less than half the length of their bodies.
-
 Family
COCCINELLIDAE - Ladybirds
Ladybirds Beetles are also known as Ladybugs and Lady Beetles. Their
adults are oval domed in shape, range in length from about 1 mm to
about 10 mm depending upon species. Like all beetles, they have their
hard forewings cover the membranous hind wings and protect the
abdomen. Their legs and their clubbed antenna are short, which are
usually hidden beneath their bodies.
-
 Family
CURCULIONIDAE - Weevils
The beetles in this family commonly call Weevil. The adults
characterized by the elongation of the front part of their head and
mouths. Their antennae usually elbowed and clubbed. They usually have
rigid bodies usually less than 10mm, although the largest can be up to
60mm. All of them are plant feeders.
-
 Family
SCARABAEIDEA - Scarab Beetles
- The beetles in this
family are usually medium to large size, occasionally with bright
colour. They have their distinctive lamellate antennae which can open
like a small fan or close tightly. Beetles in other families may have
the similar lamellate antenna but cannot be closed. Adults beetles
usually feed on leaves and flowers.
Questions for
Discussion
Why beetles are so
success?
Beetles may be success in number of species, but not quite when
counting the number of individual. When we go out to the field,
usually you will see a lot of ants, moths, flies, and grasshoppers. If
you visit some special place, such as pond, rivers, flower plants,
forest, etc, you may easily found the dragonflies, butterflies etc.
But to find a beetle may not so easily. Instead of saying beetle is a
success family, I will say they have the most number of species in
their order. So the correction question should be: Why there are so
many species of beetles?
I think of the following reasons;
- 1. The ways that we
classified all different species of beetles as one order may be not
fair. When comparing beetles with other orders of insects, I think we
put two many different families into one Coleoptera Order. We put
every insects with hard forewings into Coleoptera Order. If we put
grasshoppers, stick insects, mantids and cockroaches in different
orders, why do we put ladybird beetles, scarab, longihorn, weevil in
one order?
2. Beetles evolved in flowering season. By the help of insects, plants
invented their important organ - flower. The insects not only
consume the plants but co-evolutes with them and help plants to
develop. When flowers first appeared on earth, it was also beetles
first appear on earth. Beetles were not necessary depend on flowers
for food, however, flowers provides food for beetles and let them to
help for pollination. Flowers and beetles both benefited form each
other. Beetle species become the largest number order in Insects.
- 3. Beetle specialized in
food and live in isolated environment. After long time of separations,
different group of beetles become different species.
4. Beetles are among the first group of insect who gain the benefit of
complete metamorphosis, i.e., they develop from eggs, larva, pupa to
adult. They have two completely different body shape and there are a
lot of advantages. Those include adults and larvae not necessary
to complete for the same food and living resources, adapt to different
conditions due to seasonal changes, and to avoid predators in
different stage.
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