Wing morphometry as a tool for correct identification of primary and secondary New World screwworm fly.

Cochliomyia hominivorax and Cochliomyia macellaria are endemic Neotropical Calliphoridae species. The former causes severe myiasis in hosts while the latter is Sarcosaprophagous, but commonly found as a second invader in wounds. Due to the morphological similarity between them and the potential losses that C. hominivorax represents for cattle breeders, the rapid and correct identification of these two species is very important. In addition to a correct identification of these species, a good knowledge of C. hominivorax biology can be helpful for designing control programs. We applied geometric morphometric methods to assess wing differences between C. hominivorax and C. macellaria and conduct a preliminary analysis of wing morphological variation in C. hominivorax populations. Canonical variate analysis, using wing shape data, correctly classified 100% of the individuals analyzed according to sex and species. This result demonstrates that wing morphometry is a simple and reliable method for identifying C. hominivorax and C. macellaria samples and can be used to monitor C. hominivorax. Both species show sexual dimorphism, but in C. hominivorax it is magnified. We suggest that this may reflect different histories of selection pressures operating on males and females. Significant differences in wing size and shape were obtained among C. hominivorax populations, with little correlation with latitude. This result suggests that wing variation is also a good morphological marker for studying population variation in C. hominivorax.