Melolontha hippocastani, the northern cockchafer,[1] is a species of scarab beetle native to Eurasia, with its range spanning from Western Europe to the Pacific coast of China.

Researchers analysed microsatellite loci in over 200 individuals from three primary outbreak areas in Poland, and found significant genetic diversity within subpopulations.

[2] Mating behaviour primarily occurs during flight periods at dusk, during which beetles hover around tree tops.

One study demonstrates that male M. hippocastani are attracted to volatiles emitted by damaged leaves and conspecific females.

One research study determined that mate-finding behaviour in M. hippocastani is driven by males locating females using olfactory cues such as green leaf volatiles and 1,4-benzoquinone, along with the species' sexual dimorphism.

This finding led to further analysis on the quantities of 1,4-benzoquinone in each sex, which were found to be higher in females, suggesting its role in attracting males.

[6] Surprisingly, males were equally attracted to volatiles from both fresh and old damaged leaves, with a preference for the latter in synthetic mixture experiments.

[6] Thus, a combination of plant volatiles and sex pheromones allow for males to find feeding females in the trees, facilitating mating behaviour.

[7] Once adult female M. hippocastani lay their eggs in the soil, the larvae spend 36 months underground feeding on plant roots.

[4] The following year, in late April to early May, the adult insects emerge from the soil and feed on tree foliage.

The midgut releases hydrolytic enzymes into an alkaline and oxidative environment, which threaten the development of bacterial species.

[8] Specifically, these microbes play a crucial role in breaking down woody food components such as lignocelluloses and xylans.

A core group of bacterial phylotypes was shared between larvae and adults, indicating some degree of stability despite different feeding habits.

[8] Further research on the reactions of M. hippocastani to high manganese (Mn) content in their diet revealed significant effects on their activity and fertility.

For example, in parts of southern Germany, specifically in the states of Hessen, Rheinland-Pfalz, and Baden-Württemberg, mass breeding of M. hippocastani has been observed every 30–40 years, which causes damage from adults feeding on the foliage between April and May.

Contrarily, grubs that develop within 3–4 years in the forest soil cause severe, long-term damage on young trees by feeding on roots.

Some theories for the destructive impacts of dense shrubbery on the ability of M. hippocastani to lay eggs in the soil include: the shrub acting as an impenetrable barrier, flight imprecision of the beetle, and the use of olfaction to sense the environment as methods with which the shrubbery could impact the egg laying behaviour.