Alternative splicing of gene transcripts is an important mechanism by which genes give rise to phenotypic plasticity. Relative abundance of alternative splice forms of the calcium regulatory protein, troponin t, influences the performance of flight muscle. We characterized four alternative exons for troponin-t in flight muscle from Helicoverpa zea and Spodoptera frugiperda. Then, we tested the hypothesis that variation in alternative splicing of troponin t in flight muscle underlies the influence of diet on flight capacity in H. zea and S. frugiperda. Adult H. zea derived from larvae that fed on Bt, conventional corn or artificial diet. Adult S. frugiperda derived from rice or corn strain larvae fed artificial diet or starved for different lengths of time during the last instar. Flight capacity of moths was measured in terms of flight metabolic rate, flight behavior, mass, wing area, wing loading, and lipid content before quantifying their troponin t splice forms. Relative abundance of the largest alternatively spliced exons of troponin t in S. frugiperda is associated with increased flight metabolic rate, body mass and larval feeding success. Analyses of troponin t in H. zea are ongoing. These findings suggest troponin t as a molecular marker for variation in both larval nutrition and migratory capability.