The hidden costs of regeneration in ladybird beetles.

Insects exhibit complex physiological responses to injury, including wound healing, immune activation, and tissue regeneration, all of which impose energetic costs. Regeneration, though adaptive for survival, incurs significant physiological costs, particularly to developmental and reproductive fitness. This study investigates the developmental and reproductive trade-offs associated with limb regeneration in the ladybird beetle Cheilomenes sexmaculata (Fabricius). Third-instar larvae were subjected to leg amputation and observed through pupation to adulthood. Regenerated individuals were compared with controls across multiple traits including body weight, developmental duration, leg length, gonadal morphology, gonadosomatic index, and reproductive output. Injured larvae showed delayed development and reduced adult body mass. Although 100% leg regeneration occurred, both regenerated and contralateral legs were shorter than those of controls, suggesting systemic growth constraints. Injured individuals exhibited lower gonad weight, reduced GSI, and diminished gonadal size, with shorter and fewer testicular lobules/ovarioles. These effects were observed throughout early adulthood and varied with both sex and age, accompanied by reduced mating success and reproductive output. The observed trade-offs indicate a resource allocation shift prioritizing somatic maintenance over reproduction during regeneration. Reduced reproductive investment under injury stress highlights the need to consider internal anatomical and developmental consequences, not just external morphology, when evaluating regeneration. These findings clarify how injury-driven resource allocation shapes life-history traits and emphasize the importance of accounting for sublethal injury and environmental stress when assessing natural enemies in biological control programs.