Adult Nutrition Stress Modulates the Energy Allocation Between Migration and Reproduction in Cnaphalocrocis medinalis

Insect migration is an energetically costly process often involving a trade-off with reproduction. However, how adult nutritional stress regulates resource allocation between these two life-history traits remains unclear. Here, we compared morphological traits, flight performance, ovarian development, fecundity, and energy reserves between migrants and residents of Cnaphalocrocis medinalis under fed and starved conditions. Morphological analyses showed no significant differences in body weight, body length or forewing length between migrants and residents, regardless of nutritional status. Under starvation, migrants exhibited significantly greater flight distances and speeds than residents, and their flight distance and duration were also higher than those of fed migrants. Starved migrants showed a higher proportion of immature ovaries and higher fecundity, accompanied by a prolonged pre-oviposition period, indicating reproductive delay. Under fed conditions, ovarian development and fecundity were similar between migrants and residents. Energy reserve assays revealed that starved migrants accumulated more abdominal triglycerides but had lower thoracic glycogen than residents, suggesting preferentially triglyceride storage in the abdomen for long-distance flight. Under fed conditions, residents possessed higher thoracic glycogen levels than migrants, whereas no differences were observed in triglyceride levels. These results indicate that C. medinalis prioritizes energy allocation to migration over reproduction under energy shortage, but switches to a strategy that simultaneously meets the demands of both when nutrition is sufficient. Our findings underscore the role of adult nutrition in mediating the energy allocation between migration and reproduction, offering a scientific basis for the precise monitoring and management of this pest.