Is the major-minor male dimorphism of the stag beetle (Lucanus cervus) explained by a weaponry and wing investment trade off?

The size variation and male dimorphism of stag beetles (Lucanidae) have often been subject of studies but an ecological explanation for this male dimorphism has rarely been given or proven. As the major male clearly invests in weaponry which helps with competing with other males, we especially wonder what is the advantage of the minor morph. We hypothesized that minor males predominantly invest in wings and therefore can fly better and actively look for females. In order to test this 147 live and 164 dead specimens (including 235 males) were measured. We found a positive allometry for mandible length in major males, indicating that large major males relatively invest more in weaponry. Nevertheless, major males also exhibit the largest wings. However, minor males had a lower wing load due to their smaller body size and consequently they can probably fly better. They furthermore invest less in mandibles, giving them even a better mobility when flying on when on ground. Consequently, minor males might be of special importance in fragmented populations for exchange of genetic material.