Characteristics of larvae of the southwestern corn borer, Diatraea grandiosella, obtained from populations present in tropical and temperate regions

A comparative study was undertaken of southwestern corn borers (Diatraea grandiosella) collected from south central Mexico (19°N latitude) and southeast Missouri (37°N latitude). All the life stages of the Mexican insects were found to be larger or heavier, or both, than were those of the Missouri insects. Mexican larvae grew at a higher rate and attained a significantly heavier body weight than did Missouri larvae. Although both Mexican and Missouri larvae underwent ecdyses during diapause, Mexican larvae ecdysed more frequently than did the Missouri larvae at 23°C light:dark 12 h:12 h. Larvae that ecdysed most frequently did not necessarily spend longer in diapause. Electrophoresis of the fat body and haemolymph proteins of Mexican and Missouri larvae revealed similar patterns. The fat body of diapausing Mexican larvae contained substantial amounts of a diapause-associated protein which has been characterized previously from the fat body of Missouri Larvae. Double immunodiffusion confirmed that the diapause-associated protein of the Mexican larvae was identical to that present in the Missouri larvae. Smaller amounts of this protein appear to be present in the fat body of diapausing Mexican larvae than are present in that of diapausing Missouri larvae.