Frugal Evolution: Adaptive Reuse of Flight Muscles for Jumping in Scelionid Wasps (Hymenoptera: Scelionidae)

In many Hymenopteran species (such as ants and certain parasitic wasps), males have fully developed wings, while females are wingless due to differences in their life history strategies. These wingless females are usually unable to fly, and as a striking example of frugal evolution, their indirect flight muscles are often atrophied or completely absent. While this phenomenon is well documented in ants, it remains largely unexplored in parasitic Hymenoptera. In this study, we investigated whether the reduction of wing muscle volume correlates with reduced wings in scelionid wasps. Surprisingly, we found that although wingless scelionids have reduced or absent dorsoventral indirect flight muscles, their dorsolongitudinal muscles remain fully developed. Wingless females of Baeus and other scelionids can jump many times their body length, likely using a catch-and-release mechanism powered by the trochanteral depressor muscle. This muscle is anchored to the mesophragma via the humeral sclerite in scelionids. We hypothesize that the dorsolongitudinal indirect flight muscles act as the trigger for the trochanteral jumping mechanism in scelionid wasps, representing a possible case of biological exaptation—repurposing an existing structure for a new function.