23-June London’s Beetle Bonanza

Beetles

The range of habitats they exist in is so diverse you can almost expect to find beetles wherever you go. The obvious places such as woods, meadows, heaths, downs, marshes, lakes, river and ponds all have their own particular specialities. However, some beetles show a preference for more unusual habitats such as rotting wood, holes in trees, under bark, in moss, lichens or field crops, carrion, mould, vegetable gardens, compost heaps and less popular species in various foodstuffs, fur, carpets or furniture.

As a group they are often instantly recognisable due to their often cylindrical shape, elongated bodies and variously coloured wing cases. However, individual types often have typical features which can help in their identification e.g. rove beetles tend to have long tails, weevils their “snouts”, longhorns long antennae, water beetles large swimming legs, jewel beetles metallic colours, stag beetles horns, dung beetles clubbed antennae, click beetles their ability to jump and of course ladybirds their colourful wing cases. Others can be a lot more difficult to both find and identify due to them being either tiny or living underground, in wood, plant stems or bird and mammal nests, even mole nests.

Ground beetles Carabidae are probably the most often encountered, when they are noticed running across our paths or emerging from under a stone that we have disturbed. Two thirds of all our British ground beetles have been recorded from Bookham Common and over one hundred from Wimbledon Common including the very rare Harpalus griseus. They are often large, move fast and have a metallic sheen. The Violet Ground beetle Carabus violaceus is regarded by many as the most beautiful of all our beetles. It has bright violet markings at the edge of its thorax and wing cases with bronze and green tints. It is found in mixed woodland where it likes feeding on slugs.

Dung beetles are often stout-bodied, black beetles with clubbed antennae and grooved wing cases. The dor beetle Geotrupes stercorarius is probably the most familiar usually being found where there are cow pats. Dor means ‘drone’, referring to the noise they make when they fly at dusk. This they do more than other beetles, as well as often hitting objects. In the past they had several names including dumbledors and clock beetles. When viewed more closely, they are often carrying small, scurrying parasitic mites. Other smaller dung beetles spend most of their time underneath the cow pats, where they excavate burrows up to half a metre in length. Inside these burrows they collect the dung on which their larvae will feed. The 3-horned Minotaur beetle Typhaeus typhoeus is one impressive species that can be found on Wimbledon Common. It uses its three horns to ‘rut’ with other males over females. It prefers sandy areas where there are many rabbits. In these areas it will be feeding its young with rabbit dung down small burrows with noticeably circular entrances. Wherever there are substantial amounts of dung it is likely dung beetles are not far away.

Where there are corpses e.g. dead fledglings, carrion beetles can sometimes be found. They lay their eggs on dead carcasses and their larvae then eat the corpse. Most are black or brown, but some have striking orange red markings on their wing cases. The four spot carrion beetle Dendroxena 4-maculata is easier to identify than most and can be found in Epping Forest where, as an adult, it goes on to eat the caterpillars of green oak roller moths. Rove beetles Staphylinidae tend to be long brown or black beetles that get noticed because when disturbed they raise their ‘tails’ in a challenging manner.

The most famous is the devil’s coach horse or cock-tail Staphylinus olens. It was thought this formidable beetle could kill on sight and also deliver a curse at the moment it raised its ‘tail’. Other rove beetles emit a noxious liquid from near their anus, whilst many others just bite. Except for the devil’s coach horse, which is 25 mm long, they tend to be smaller between 1 and 4mm in length. They are usually found near decaying material, where they will be feeding on fly larvae. Other beetles are associated with ants and yet others again with fungi.

Tiger beetles Cicendela spp. which are often brightly coloured are usually seen running across the surface of sandy heaths e.g. Oxshott heath in open, sunny situations. These are large, often metallic green beetles that have dangerous looking mandibles and are famous for the speed at which they run. This can be as fast as half a metre a second and, size for size, this is faster than a cheetah. They used to be called ‘sparklers’ or ‘earth gluttons’.

Surprisingly a quarter of all British beetles are weevils although with most being so small and secretive we rarely see them. They are all vegetarians and many are highly destructive to crops. No part of a plant seems to be out of bounds including petals, bark, fruit, seeds and roots. It is often in seeds or grain that we first encounter them. They usually make little attempt to escape just tending to drop to the ground where they then become quite hard to find. It is usually their long distinct snouts and antennae that look a little like television aerials that allow us to identify them. At the end of these snouts, which often curve downwards, there are jaws which are used to bore holes into plants into which they often then lay their eggs. On the whole they tend to be grey or brown but occasionally have brightly coloured metallic scales which often rub off easily revealing a black beetle underneath.

Acorn weevils Curculio glandum (6 mm.) can now be found on oak trees. They pierce young acorns with their jaws and then lay an egg inside. The larva then feeds off the inner seed leaves before boring out and pupating in the soil perhaps when the acorn falls. A similar species Curculio nucum attacks hazelnuts and C. pyrrhoceras prefers to lay its eggs in oak galls. One of the largest weevils to be found in London is the red-legged weevil Otiorhynchus clavipes (11 mm.) which is a pest in gardens on strawberries.

Weevils in the genus Phyllobius tend to be more colourful. The glaucous leaf weevil P. calcaratus (10 mm.) can be either light or dark green, golden-grey or even emerald in colour. It lives on fruit trees where its presence may be indicated by small holes in the petals. P. pomaceus (8 mm.) which prefers to feed on nettles can be either bluish in colour or a metallic green with or without gold or copper tints.

Weevils often have a particular plant they prefer to feed on which can make them a little easier to find. Anthonomus pedicularis (4 mm.) is an orange or red-brown weevil that prefers hawthorn. Ceutorhynchus erysimi although small (2 mm.) is a handsome green iridescent species that is often found on Shepherd’s purse.

Several weevils like living on figworts of which Cionus scrophulariae (5 mm.) is probably the most common. Among the raised lines on its back it has a large black noticeable dot.

Other more unusual species include the red oak roller and various fungus weevils some of which look like bird droppings. The red oak roller Attelabus nitens (5 mm.) is bright red and lays its eggs on oak leaves before rolling over the edges of the leaf to protect them. Platystomus albinus (8 mm.) is often found in the fungus called King Alfred’s cakes where it could easily be confused for a bird dropping. All the species mentioned can be found in London but at this time of year to find weevils it is just better to sweep favoured food plants such as oak, hazel, hawthorn, nettles and mints.