Melolontha melolontha (Linnaeus, 1758)
This widespread species occurs throughout Europe from Portugal east to Turkey and Ukraine and north to southern Scandinavia, and there are a few records from Siberia, northern India and China. It was once abundant throughout its range and on occasion, even regularly in many areas, it became a very destructive pest of crops and amenity grassland but changes in mechanical agricultural methods and the widespread use of insecticides have drastically reduced the numbers so that towards the end of the 1970’s it was reduced or even eradicated from many areas of Europe and was no longer regarded as a pest. On the other hand there has been a recent increase in numbers probably due mostly to legislation since the 1980’s restricting the use of agricultural chemicals. In the U.K. it remains locally common throughout England and Wales, though in nowhere near its former abundance, and there are scattered records further north to the Scottish Highlands. Adults appear in early May and, because of the species long life-cycle, there are years of great abundance although this varies regionally and there is a longer cycle of around 30 years in which they occur, or at least did occur, in huge numbers. The typical habitat is broadleaf woodland margins, especially near arable or open grassland, wooded parkland and gardens etc. Adults rest during the day among foliage and fly towards feeding sites at dusk; they fly individually but large aggregations may appear swarming around and feeding upon the leaves of an individual tree which may then show severe defoliation, they are voracious feeders and will typically attack the young leaves of oak but a wide range of species have been recorded as hosts and there are records of them feeding on conifer needles. The males are strongly attracted to light and regularly appear in suitably placed moth traps and entering illuminated windows. They become mature after a week or so of feeding and mate during early or mid May, the mated females then fly away from their feeding sites towards open grass or crops where they will lay about 20 eggs among roots in the soil at a depth of between 10 and 20 cm. Many females die after ovipositing but some return to the trees and feed before ovipositing for a second or third time and some may lay up to 80 eggs during her lifetime. The
adult season is generally over within five or six weeks. The larvae hatch towards the end of June and immediately begin to feed on small roots, at this time feeding and growth is rapid and they may move through 30cm of soil each day in search of food. With the onset of cold weather the larvae move deeper into the soil, between 20 and 100cm, where they cease feeding and overwinter. Second year larvae work their way up through the soil during April and May and resume feeding voraciously until the autumn when they will descend and overwinter for a second time. During their third year they continue feeding, often near the surface, until June or July when they will burrow deeper and pupate in an earthen cell, the adults are fully formed by August or September but remain buried until the following spring when they make their way to the surface and fly in search of suitable host foliage. The life-cycle takes about 36 months spread over 4 years in temperate regions but in cooler areas may require an extra season of larval development, again with pupation in the summer and adults emerging the following spring. In numbers the larvae can be extremely destructive in a wide range of crops such as potato tubers and root crops, various cereals and grasses generally, the roots of fruit trees may be stripped and grape vines may be completely destroyed over large areas.
The large size, 20-30mm, and general appearance of our two Melolontha species is distinctive among the U.K. fauna; the only confusion might be with another common chafer genus, Amphimallon, but these are smaller, 15-20mm and have a 3-segmented antennal club. The antennal club of the male cockchafer has seven lamellae which are about 3.5mm long; in the female it is 6-segmented and about 1.5mm in length. Most specimens are chestnut brown but for the head, pronotum and scutellum which are darker. The anterior margin of the clypeus is strongly raised and usually pale compared with the rest of the head, and the first and third antennal segments are much longer than the second. The head and pronotum have recumbent yellow pubescence while that on the elytra is white and much shorter. The elytra are finely punctured throughout and each has four longitudinal glabrous carinae. Each abdominal sternite has a well-defined triangular patch of pubescence on the lateral margin and the pygidium is elongate and narrowed to the apex; much longer and rounded apically in the male, broader and truncate in the female. In the closely similar M. hippocastani (Fabricius, 1801) the pygidium is constricted before the apex.
Antennal club 3-segmented.
Abdomen without lateral white patches.
Summer species (June - August)
Fig. a) M. hippocastani (left) and M. melolontha (right) male pygidium.