Differences in Wing Morphometrics of Lymantria dispar (Lepidoptera: Erebidae) Between Populations That Vary in Female Flight Capability

All male gypsy moths, Lymantria dispar L., are capable of strong directed flight, but flight in females varies, increasing from west to east geographically across Eurasia. To better understand how the wings differ between female flight capable and flightless strains, a wing morphometric analysis of 821 gypsy moths from eight geographic strains (three Lymantria dispar dispar L., four Lymantria dispar asiatica Vnukovskij, one Lymantria dispar japonica Motschulsky) was performed. Body mass; length and width of both fore- and hindwing; and wing area, aspect, and loads were measured on both sexes from each strain. Gypsy moths were sexually dimorphic; females had a higher wing load, larger aspect ratios, bigger wing area, and heavier body mass than males. Wing loads of females, but not males, differed significantly among geographic strains and were lower in flight capable strains. Wing aspect was less variable within each sex among the strains. Female fore- and hindwing area were both larger in strains with strong directed flight capabilities compared with flightless strains, suggesting both fore- and hindwing areas play significant roles in flight. A logistic regression model using female forewing length and wing load correctly predicted the female flight capability of the source strains >97% of the time and may be a useful tool to use in conjunction with molecular methods for detecting introductions of Asian gypsy moth. None of the male morphometric wing characters were found to reliably predict the female flight capability of the source population.