Beetles on Gorse and Broom
Sampling beetles from these plants has many advantages for the beginner; firstly the plants are readily recognized and usually obvious even at a distance, secondly they are common and widespread and will soon be encountered in the field, and lastly the beetle fauna tends to be restricted to these plants, meaning identification is usually straightforward. Having said that the fauna is rather small but this has its own advantages in that the beginner will usually have not encountered the species elsewhere and that some of them, e.g. the Scolytids, provide a readily identifiable introduction to an otherwise difficult group of beetles. Gorse is an evergreen shrub that grows in thickets up to 2m tall and may flower continually through the year, it is generally impenetrable because of the dense growth and rigid sharp spines which cover the branches but it is usually easy to insert a beating tray or sheet under the branches or to sweep the softer foliage with a net. There are three species of gorse in the UK; Common Gorse, Ulex europeus, occurs throughout, is generally common everywhere and is the classic Gorse that forms thick impenetrable growths, Western Gorse or Dwarf Furze, U. gallii, occurs throughout the west of England, Wales and Scotland, being rare elsewhere except around the coast of Norfolk and Suffolk, it usually grows to around 50 cm. Dwarf Gorse, U. minor, which grows to about 30 cm and often
Common Gorse on Bricket wood common, Herts.
occurs among heather on moorland, is a much more local and sporadic species of south and southeast England, Wales and Scotland. Ulex is a genus of the pea family, Fabaceae, and as such develops conspicuous seed pods in which insects develop and which, on hot and dry days, can be heard popping open. Another genus of the Fabaceae needs to be mentioned, the closely related Genista L, species of which are generally referred to as brooms but two species have acquired common names; Petty whin, G. anglica L. is a local species of Cornwall, Wales and eastern Scotland while Dyer’s greenweed, G. tinctoria L. is widespread but mostly western in the UK, both are known to host several UK beetles.
Common Broom, Cytisus scoparius
Cytisus scoparius or Common Broom is another member of the Fabaceae, it is generally abundant throughout the UK except for parts of the midlands and West Country and is quite unmistakable, especially when in flower during the spring and early summer, at other times its dense long and soft branches are distinctive. Sampling is very easy; a beating tray or sheet is placed beneath the plants and the branches are tapped, and because the plants are not very tall most of what falls will end up on the sheet although this will include a fair amount of debris. Many of the beetles will remain still for a while and will be very hard to spot, although this becomes easier with experience, but if a warm, sunny day is chosen they do not remain motionless for long, and anyway it is easy to get comfortable and spend a while looking, it’s also a good idea to take a large magnifying glass and a pooter for the small stuff. The best plants to sample are older and larger ones which have a fair amount of dead wood among the stems. Many beetles are attracted to the bright yellow flowers e.g. Meligethes aeneus (Fabricius, 1775) and several species of Agriotes Eschscholtz, 1829 will often be present in numbers, a selection of ladybirds will be found on the stems and
in the flowers, e.g Hippodamia variegata (Goeze, 1777) and locally we very often find Prosternon tessellatum (Linnaeus, 1758) among swept foliage, but beyond these adventitious species there are a few beetles so closely associated with these plants that they will only rarely occur elsewhere and the host association is an excellent guide to their identity i.e. species that might be very difficult to identify otherwise might be readily named due to their host, and after a while this rather limited fauna will become familiar and easily listed when surveying unfamiliar sites. The following is a guide to those species generally associated only with the listed hosts.
Exapion difficile (Herbst, 1797)
Exapion genistae (Kirby, 1811)
Stenopterapion scutellare (Kirby, 1811)
Sitona striatellus Gyllenhal, 1834
Hypera venusta (Fabricius, 1781)
Cryptolestes spartii (Curtis, 1834)
Tychius parallelus (Panzer, 1794)
Strophosoma capitatum DeGeer, 1775)
Sitona striatellus Gyllenhal, 1834
Charagmus griseus (Fabricius, 1775)
© Arved Lompe
© Lech Borowiec