The Male Beetles That Fight Each Other With Their Legs
In southeast Asia one beetle species is notable for its extremely large hind legs. The frog-legged leaf beetle (FLLB) uses its hind legs to support itself in vertical positions while feeding on plant leaves and stems. Given the beetle’s name, one would think that their legs allow them to jump. Actually, the FLLB’s legs are not even used for crawling; instead they are used by males as weapons. The hind legs of these beetles are covered in prickly hairs that allow for a more secure hold on plant stems while feeding. Females also possess the hairs. In fact, the females’ hind legs are identical to the males, but with one exception. The male hind legs are enormous, and clearly out of proportion with their body size. This size difference exists as a result of sexual selection. It turns out that female FLLBs are quite turned-on by large hind legs in a male.
The female FLLB’s preference for larger hind legs in a male makes sense given that larger hind legs are a highly advantageous feature. Male beetles will use their legs to fight other male beetles. In the insect world, fights between male beetles are not broken up by their girlfriends. During combat, large hind legs deal the most damaging blows to an enemy. When it comes to FLLBs, the males with the largest hind legs will always win both the fight and the female. Female beetles always choose the winner of a fight, which is why male FLLBs have grown progressively larger legs over the course of evolution.
Technically, researchers have never witnessed a battle between two FLLB males, but they have witnessed several fights between males of a closely related beetle species that sport similar oversized legs. These close relatives belong to the Coreidae family. Researchers have noted that Coreidae beetles will also fight over food. This also lends itself to sexual success, as females require abundant food sources in order to survive and lay healthy eggs. These beetles have been repeatedly observed in fights that begin with one male attacking another male without provocation. The males are often observed beating other males with one of their giant hind legs as though they are a pair of clubs. Male beetles belonging to the FLLB species and beetles in the Coreidae family are considered to be among the most violently competitive beetles known to science.
Have you ever witnessed two insects of the same species engaged in battle?