Common Cockchafer

• Because its larvae take three or four years to develop, the adults appear in cyclical waves every three or four years, and the years vary from region to region according to climate.
• In 1320, in Avignon, its larvae were put on trial and sentenced to exile in a special reserve; when they failed to comply with the decree, they were gathered up and exterminated.
• The males locate the females by the volatile compounds released by leaves as the females eat them.
• Its cycle lasts three or four years, and because it is synchronised it appears in massive waves every three or four years in any given district. Those periodic outbreaks have been documented in Europe since the Middle Ages.
• They were a feared historical plague: there are medieval records of ecclesiastical court proceedings against cockchafers, which were even excommunicated.
• The larva, known as the white grub, is the damaging stage: it lives in the soil and eats the roots of cereals, grassland and fruit trees, and can kill the plant from below without anything showing above ground.
• The adult emerges in spring, flies at dusk with a very characteristic heavy drone and devours the leaves of oaks, beeches and fruit trees.
• Its populations collapsed with the insecticides of the 20th century and have partially recovered since their withdrawal.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat & environment

Lowland and low-altitude country, scarce in the mountains. It prefers wooded ground, fields and orchards on light soils. The adults overwinter buried between 20 and 100 cm deep

Size at birth

Oval eggs of 2-3 mm, dirty white, laid on the ground in batches of 10 to 30

Gestation / incubation

The eggs hatch four to six weeks after laying

Litter / clutch size

Batches of 10 to 30 eggs buried 10-25 cm deep. Three larval stages that take three to four years to complete

Sources consulted: ITACyL - Portal de Plagas de Castilla y León; Koppert; Sociedad Entomológica Aragonesa (Boletín 44); EPPO Global Database; Malusá et al. 2020, Organic Agriculture 10

Best time: From April to July, mainly in June, on mild nights and near lights