Morphometric differences between rice and water-oats population of the striped stem borer moth, Chilo suppressalis (Lepidoptera: Crambidae)

Abstract

The striped stem borer moth, Chilo suppressalis, has two major host plants; rice, Oryza sativa, and the water-oats, Zizania latifolia. It has been suggested that there is reproductive isolation between the populations feeding on rice (rice population) and water-oats (water-oats population). We compared the morphological characteristics of the two populations using multi variate analyses based on eight genital and ten non-genital traits in male adults. Body size differed between the two populations as shown previously. However the results of a principal component analysis (PCA) based on genital traits showed a proportional difference between the two populations, but not on the non-genital traits. This shows the existence of a morphological difference in the genitalia of male adults between the populations. We also conducted a discriminant function analysis (DFA) based on seven genital and five non-genital traits. The discriminant function obtained could classify the two populations with 94.3% accuracy. Another discriminant function using only four genital traits also could distinguish the two populations with 88.6% accuracy. DFA would be of use in the practical forecasting of occurrence.