The relationship between the fruit-feeding noctuid Heliothis subflexa Gn. (Lepidoptera: Noctuidae) and its host plants in the genus Physalis L. (Solanaceae) is special. In nature, H. subflexa caterpillars feed exclusively on fruits of Physalis. As a defining trait of the plant genus, the fruits of all Physalis species are enclosed in an inflated, lantern-shaped calyx. To feed, each newly emerged H. subflexa caterpillar cuts a small hole in the calyx and then bores into the fruit. Once inside, the caterpillar spends the majority of its time sheltered inside of the fruit’s husk. Previous studies suggest that the calyx and certain other characteristics allow H. subflexa to escape both natural enemies and direct competitors.

Over the past four years we have collected four seasons worth of field data on H. subflexa infestation to over 100 naturally occurring field populations of Physalis plants in North Carolina, Florida, Texas and Mexico. We have conducted four separate common garden studies in North Carolina and Mexico. We have also carried out laboratory assays on larval survivorship and female oviposition using 25 different species of Physalis. The data that we have accumulated demonstrates that some Physalis species are consistently not viable hosts for H. subflexa, and many other species are only marginal hosts. I will present our findings on how plant characteristics influence H. subflexa’s host range. I will also discuss how these plant characteristics relate to pressure from natural enemies and competitors.