MERRY, J. W.*; KEMP, D. J.; BERTRAM, S. M.; RUTOWSKI, R. L.; Arizona State University; Arizona State University; Arizona State University; Arizona State University: Butterfly growth and development: the role of phosphorus

Phosphorus concentration in developing organisms is often tightly correlated to growth rate, and may be the primary factor that limits how quickly individuals of many species grow. We raised Orange Sulphur butterfly larvae, Colias eurytheme, on young and old alfalfa leaves. These two diets affected many aspects of their development, resulting in larger body size and shorter development time among individuals raised on the higher quality, young alfalfa diet. To test the hypothesis that phosphorus limitations were responsible for the differences in growth rates, we assayed phosphorus in 40 adult specimens (20 on each diet) from the rearing experiment. As predicted, we found a significant, negative relationship between phosphorus concentration and larval development time. Nevertheless, we did not detect a significant difference among diet treatments in adult phosphorus content. Therefore, while phosphorus may have been an important determinant of development time, it does not appear that our diet manipulations were responsible for this difference. An interesting finding of this study was that male abdomens were unusually phosphorus rich (2.2% vs. ~1% in other tagmata, including virgin female abdomens). Since males provide females with large spermatophores, we proposed that the high abdominal phosphorus in males might be related to a nuptial gift of phosphorus to females. However, we found that spermatophores, while variable, were generally phosphorus poor (mean 0.6%). Therefore, while it is still possible that phosphorus is transmitted in the other components of the male ejaculate, it does not seem to be a major component of the spermatophores.