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Teaching children about nature---Coleoptera  the beetles

Coleoptera is an Order of insects known commonly as beetles. The main features of the Coleoptera {from the Greek Koleos, meaning a sheath+ pteron meaning a wing}  refers to the horny consistence of the upper pair of wings. the whole body is likewise covered with a 'crust' of a similar nature, more or less rigid, chiefly of a peculiar  substance known as chitine.

This hard covering protects the internal organs, and act in the way that bones work in the human body that is to say it supports the softer parts and allows a place for the muscles to be attached.

Beetles in common with all other insects have three separate parts that make up the whole body. These are the head, thorax and abdomen. We will start by looking at these three parts.

The Head---The head appears as a single part without any obvious division. It is generally harder than the rest of the body. The shape of the head is most commonly triangular with the angle somewhat rounded in many species. In one important group the Circulionidae {see hazel nut weevil} ,it is produced into an elongated snout called a rostrum. The back part of the head is attached to the thorax in such a way as to allow a great deal of movement in almost any direction.

The front part of the head is occupied by the mouth and its various parts. near to the mouth is placed the eyes and the antennae. The mouth is more complicated in its structure than those of higher animals and its various parts tend to differ in the various groups of these insects. However, here are the basic parts of the mouth----

They consist, essentially, the Labrum {upper lip} the mandibles, the maxillae {lower jaws} the Labium {under lip} and the mentum. The Labrum {upper lip} is a small movable piece placed on the upper side of the mouth, and closing it from above. it is variable in shape, usually wider than it is long, and sometimes rounded or triangular. It is often hard and its outer margin frequently notched.

The mandibles or upper jaws are made up of two strong, horny, pieces which are placed one each side of the mouth, immediately below the upper lip, which usually covers the base. They are more or less curved towards the tips and usually toothed or serrated on their inner edges. they may be said to represent the jaws in vertebrate animals, but they differ in their movement. instead of moving up and down like other animals, and indeed our jaws do, they move from side to side.

The most obvious parts of the head are the two, jointed parts that stand away from the head-the antennae. These never exceed two in number in genuine insects. they are placed in front of, and rather beneath the region of the eyes. The antennae consist of joints {usually eleven}, but are vary very much in their length.

The usual length of the antennae may be said to be about half the length of the body, but they are often shorter. However, in the Capricorn group of beetles they are distinguished by the length and delicate structure of the antennae which are often four times longer than the body. 

Note the length of the antennae in this species.

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The thorax

The next part of the beetle, that requires some attention, is the thorax, the portion of the body which is placed between the head and the abdomen. The thorax is the part of the beetle to which the legs and wings are attached, therefore the thorax is the creatures part that provides movement, either walking of flying. The inferior part of the thorax is the sturnum or' breastbone ' ; it is much more developed in some groups, particularly the water beetles which make up the genus Buprestris. On the back part of the thorax, the only part that can be seen from above, is commonly triangular shaped, with its point projecting backwards, this is called the scutellum.

The true organs of flight in the Coleoptera are two membranous and transparent wings which are joined to the upper part of the thorax. they are generally quite large and are extended by means of a few strong nervures which run length ways along the wing and throw out a few lateral branchlets. While at rest or not in use the wings are folded, and in most cases completely covered by the first or upper wings. The upper wings are of a hard ,horny substance, similar to the 'crust' that covers the head and thorax, and in the language of entomologist {those that study insects} they are called elytra {wing cases}.

The elytra  are like wise attached to the thorax and when at rest they are folded along the back of the abdomen, in the middle of which their internal edges meet and form a straight line. The elytra usually covers the whole upper surface of the abdomen which, being sufficiently protected by their means is rather of a soft consistence. Without this protective elytra the wings used for flight would be continually liable to injury, as their delicate texture is not designed to resist the injuries they would be exposed to as they hide beneath stones or bury into the loose earth.

The elytra also serve to protect the small round openings which are located along both sides of the abdomen  which allows air to pass through by which means they breathe. they do not breathe through the mouth or nose as we do. 

In the larger beetles the  wings seem to be very small compared with the size of the body. The flight therefore seems laborious and is seldom carried out for long distances. When they rise they rise very slowly, before gradually picking up speed, however, frequency which they bump into things, directly on their flight path, shows they do not possess the power to change direction quickly, even if they sense or see the object.

many of the smaller beetles, and those whose habits require a long flight or sustained flight, such as the tree chafers  { Meldontha} have very strong wings. During a warm day in spring the air is filled with small beetles, which flit about in the sunshine.

Chafer beetles have strong wings

Thorax--legs

In beetles as in all true insects, they have six legs. The legs are made up of four 

observable pieces. These are the coxa [haunch}, the thigh, the tibia and tarsus {the foot} We will look at these individually.   The coxa is the joint which joins the leg to the insects body at the thorax.

The thigh is the largest portion of the leg. It usually looks flattened and with spines on the edges. The tibia are generally shorter and thinner than the thighs, but they do grow thicker at the very lower end. They tend to be triangular in shape and are frequently covered by tiny stiff hairs that are known as bristles and also tiny spines known as spurs. The tarsus is the end of the foot and is made up of small joints some species have three others four or five. 

Beetles come in all shapes and sizes

Beetles come in all shapes and sizes

The Abdomen

The third and last part of the body is the abdomen another very important part of the body. it is generally the largest part of the insect and is joined to back part of the thorax. Unlike the thorax the abdomen has no legs or wings attached to it. It is made up of rings or segments. Along both sides of the abdomen are rounded openings or breathing holes used by the insect to breathe through as already mentioned above.

Many beetles have a tubular, retractable part, right at the end of the abdomen which is known as the ovipositor. This is in the form of a little tube and it is used for placing the eggs safely, where the female knows they have the best chance of hatching. No beetle species in the UK possess a sting.

The abdomen is larger in the females than in the males, and they differ in form with the terminal {end} segments,besides, having fewer than the males.

In the next article { beetles-2} we will review some the species {kinds} of beetles that form this large group of insects.

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