Host plant availability for herbivorous insects can vary dramatically due to local plant community composition. Polyphagous insects may be restricted to single-host plant diets due to limited dispersal mechanisms and patchy host plant distributions. Epimecis hortaria is a polyphagous moth that feeds on tulip poplar, spicebush, sassafras, and pawpaw. With varying host plant distributions spanning the eastern United States, it is likely that some E. hortaria caterpillars experience functional monophagy. Previous research indicates that monophagous diets significantly affect E. hortaria maximum larval weight, adult weight, and weight loss during pupation. In this study, we measured water and fat content of 18-day old E. hortaria larvae and newly eclosed adults raised on single host plant diets of tulip poplar, spicebush, sassafras, and pawpaw. We determined water content by measuring weight loss of sacrificed larvae after 24 hours in a drying oven. Fat was then extracted from the dry biomass using petroleum ether and weighed.
Results/Conclusions
Preliminary results indicate that host plant diet significantly affects larval water content (p<0.001), but not fat content. These findings suggest that significant differences in total larval weights between treatments groups (p<0.001) may be the result of differences in caterpillar water content. Understanding how monophagy might affect water and lipid storage in lepidopteran species could be useful in determining the overall importance of host plant availability in patchy environments, especially in conservation efforts to protect threatened or endangered polyphagous insect herbivores.