Beetles (order: Coleoptera)

Asked what could be inferred about the work of the Creator from a study of His works, the British scientist J.B.S. Haldane is reported to have replied, that He has "an inordinate fondness for beetles." Some people suggest that Haldane never uttered these words, but no one can argue with the truth they contain.

Using sheer numbers as a criterion for success, beetles are the most successful animals on Earth. As the largest group of insects, they represent a fifth of all living organisms and a fourth of all animals, epitomising diversity. Nearly every biological strategy used by terrestrial animal life is represented in this remarkable group of animals.

By the most conservative estimate, approximately 350,000 species of beetles have been described since 1758. That's an average of slightly more than four per day. Of the 27,000 species of insect in Britain, beetles are our third largest order with between 3,900 and 4,500 species.

Sarah Beynon - Cetonia aurata

Identifying beetles

British beetles range in size from less than 1mm to 40mm long. The vast majority of beetles can be distinguished from other adult insects by the following two characters:
1.The forewings are reduced to hard or leathery elytra (wing cases) which usually meet on the centre-line of the abdomen. Aristotle described thus named them Coleoptera, from the Greek koleon, "sheath", and pteron, "wing".
2.They have biting rather than sucking mouthparts

Beetles are unlikely to be confused with any other order, except the Hemiptera (true bugs). There are some beetles with elytra reduced or even completely absent. These can look superficially like immature bugs, although bugs always have sucking mouthparts (a rostrum) instead of biting mouthparts.

Identifying beetles to family level is achievable by the amateur, using an AIDGAP Key such as that produced by the Field Studies Council (Unwin, D.M. A key to the families of British Beetles.) It will be necessary to have access to a microscope, as many identification features are on the legs and antennae. It is needless to say that it is impossible to count the number of leg-hairs on a beetle that is in its entirety less than a couple of millimetres long without a microscope!

However, identifying beetles to species level, although possible in some cases is not easy without a good text, and a good teacher. Many beetles look superficially the same, and it is often necessary to dissect them and use internal characters for correct identifications. It is therefore not possible to look at a general British insect text and identify a specimen to species (except for some of the larger, charismatic species). However, although identifying beetles to species is challenging, it is relatively easy to learn what to look for and ‘get your eye in’.

Sarah Beynon - Timarcha tenebricosa

Collecting and storing beetles

Collecting

Beetles may be collected from the field in a number of ways. As well as collecting by hand, beetles may be sucked up with a pooter, beaten from vegetation onto a plain white sheet, prised out of wood with a knife or swept with a sweep-net.

Traps are a very good way of encouraging beetles to catch themselves. Pitfall traps are the most widely used and effective beetle traps, as they sample a wide range of species that are often not found whilst hand-collecting. They may be used with or without a bait. A basic pitfall trap is a plastic cup, which is sunk into the ground so that its top is level with the surface. Beetles may be collected live, or killed in the trap. To kill everything that falls in the trap, use antifreeze (ethylene glycol) as a killing fluid and add a couple of drops of detergent to stop the beetles floating. A “roof” can be erected to keep rain out. Simply use garden stakes to position a paper plate over the trap, leaving a good 10cm between it and the ground. A series of 5 or 10 traps (at least 2m apart) is best set out in any one locality, either randomly or in a line.

Sarah Beynon - pitfall trapping

Baited pitfall traps also produce interesting finds. Placing rotting fruit/vegetables/ fungi/carrion in a pitfall trap will attract a diverse fauna. However, do not put a killing agent in the trap with the bait! Live specimens must then be removed from the trap by hand on a daily basis. Dung (usually 30g) may be placed in a trap, or suspended in a cheesecloth bag above it (this allows a killing agent to be placed in the trap). A number of interesting dung beetles should be attracted: Do remember to note the type of animal from which the dung originated, as many dung beetles are specific to certain types of dung!

Flight intercept traps produce specimens that are not normally encountered by other collection methods. A sheet of black polyester marquisette material can be suspended vertically between two stakes or trees. A line of containers filled with killing fluid should be placed under the trap, so that beetles fly into the sheet and fall into the containers.

There are also many other ingenious trapping methods. Piles of fungi and decaying fruit/vegetables can be left and regularly sifted over weeks. Carrion may be placed on the top of a tin filled with sand, which can be sifted through often to find a very rich fauna. Lawn mowings may be placed in paper sacks or plastic bags for a few days to rot, and then placed in piles at the base of trees. After a week or so and at intervals thereafter, the pile can be sifted.

In order to examine beetles it is necessary to kill them. Individual, hand collected beetles can be killed by placing them in a tube of alcohol or antifreeze (ethylene glycol). They may also be killed in a killing jar. This can be made by casting a layer of plaster of Paris at the bottom of a glass jar. The plaster will absorb a killing agent, such as ethyl acetate.

Storing

Beetles may be stored in alcohol, pinned or mounted on cards. Alcohol storage is probably preferential, as there is no possibility of specimen degradation. Keeping the tubes in the freezer should also increase their shelf-life. If specimens are to be dry-mounted, it must be remembered that they must be dried thoroughly, otherwise they will go mouldy. Popping them in your airing cupboard for a week should do the job!

A good source of information on storing your specimens is ‘A Coleopterist’s Handbook’ by Jon Cooter (new edition just out). All equipment, such as pins and cards is available from entomological suppliers, such as Alana Ecology.

For any information/advice/questions on anything regarding beetles, please contact the county recorder, Sarah Beynon: sarah.beynon@hotmail.co.uk