Melolontha hippocastani Fabricius, 1801
This is a very widespread European and Asian species extending east to the pacific coast of China, though generally less common than the cockchafer where their ranges overlap it is nonetheless sometimes a serious pest of upland cereal crops etc. and fruit trees in northern latitudes and large infestations have destroyed areas of young pine trees. Essentially a forest species; through the Taiga and more southern steppe forest in central and northern Europe it may be abundant in forest clearings on light or sandy soils while further south it occurs in dense and shady upland wooded areas. Males are strongly attracted to light which makes the species relatively easy to survey and trap in order to help control infestations. The adults appear a little later than the cockchafer and this varies with latitude; in the south they occur from April to early June while further north from May to the end of June. Maturation feeding generally occurs among deciduous trees on wooded margins, often with individual oaks hosting large numbers. Mated females repeatedly fly short distances to oviposit in clearings or close to the margins, they choose light open soils and lay up to 70 eggs at a depth of 10-100mm and each will return to feed and lay 3 or 4 times. Larvae emerge after about 6 weeks and initially consume organic matter before feeding on roots, they will consume the roots of most herbaceous and woody plants and the most serious damage is caused by second and third instar larvae during the second year, their development generally takes three years but in cooler latitudes 4 or 5 years is not unusual. Pupation occurs in an earthen cell deep in the ground towards the end of July and the adults are fully formed after 4 to 6 weeks but remain underground until the following spring when they will emerge in response to increased temperature and fly in search of suitable foliage for maturation feeding. Adults are nocturnal, remaining in the canopy during the day and often returning in numbers to a single tree over several nights; here they may be seen swarming around the canopy of a range of broadleaf trees but in particular oak and especially when these have young emergent foliage. In commercial agriculture and horticulture they were formerly a serious pest in northern latitudes but the widespread use of organophosphates and light traps has drastically depleted their numbers in sensitive areas.
In the U.K. it is a species of deciduous and mixed upland forests; there are records from North Wales, Northern England and Scotland and a very few from Northern Island but most of these are historical and there have been very few since 1990.
Easily recognized among the U.K. fauna as a Melolontha, this species is very similar to the cockchafer but on average smaller and less variable in size, 22-27mm. The male antennae have 7 lamellae of about 4mm while the female has 6 at around 1.5mm. Males differ from cockchafer males in having the apex of the third antennal segment produced into a short spine. The pygidium is constricted before the apex in both sexes.
Fig. a) M. hippocastani (left) and M. melolontha (right) male pygidium.