Thermal effect on larval development of the European stag beetle, Lucanus cervus

Conservation of the threatened and protected European stag beetle (Lucanus cervus) mainly focuses on the availability of dead wood as larval habitat. However, as the larval ecology of this species remains poorly studied, less attention has been given to other habitat requirements such as ambient temperatures for the development of the larvae. To design proper guidelines for the preservation of this iconic species, the growth of stag beetle larvae is compared between outdoor containers under a warm sunny and those in a cold shady treatment. Populations originated from the Veluwe (Netherlands) and Colchester (United Kingdom). The shady microclimate led to lower temperatures, which resulted in higher larval weights before molting and an additional year to complete larval development for a part of the population. However, weights were lower than in the warm microclimate when comparing larvae from the same age. This is explained by the longer development time for the different stages. Finally, we found higher larval weights for larvae originating from the Veluwe (Netherlands) compared with larvae from Colchester (UK). We conclude that larvae of L. cervus can cope with shady, colder microclimates. Larval development time in general takes two to three years and depends on temperature. Larvae grow mainly in the warm season while weight remains constant, or even decreases, during the cold season with an approximate threshold between 10 to 15 C.