(2nd Place) Ultrastructural morphology of blow fly (Diptera: Calliphoridae) ommatidia

Blow flies (Diptera: Calliphoridae) possess high visual acuity that, in conjunction with highly evolved olfaction, allow them to locate important resources, like carrion and mates. However, high-resolution morphological studies of blow fly ommatidia are lacking. This pilot study aimed to capture scanning electron microscope (SEM) images of several blow fly species common in the southeastern United States to assess for variation in ommatidial morphology. Wild adult blow flies were bait-collected in Knoxville, TN and were freeze-killed at -20°C. Decapitated heads of one male and one female of five different species were examined in this study: Chrysomya megacephala (Fabricius), Chrysomya rufifacies (Macquart), Cochliomyia macellaria (Fabricius), Phormia regina (Meigen), and Lucilia sericata (Meigen). Heads were sputter-coated with gold and viewed via SEM. The same core series of images ranging from 25X to 7,000X magnification were taken for each sample to assess any variation present between sex and species of flies. Ommatidial facets were primarily hexagonal, with some square facets also present in all species except C. rufifacies. All species possessed sporadic interfacetal setae between each ommatidial facet. Overall, there was little variation in ommatidial morphology between species or sexes, with exception of sexual dimorphism in C. megacephala which has been previously documented. Preliminary results indicate little variation in the selected species examined thus far, though increased sample size as well as the inclusion of additional species from all prominent North American subfamilies will allow for better interpretation of ultrastructural ommatidial morphology among blow flies.