Amber Emerson, 2013

Howard University

Prey consumption and effects on performance in the specialist frugivore Heliothis subflexa

Omnivory has been found to be especially prevalent among insects and is thought to have evolved as a way to overcome the low nutrient intake that an herbivorous or predaceous diet alone may have. However, some insects engage in omnivory less frequently than others. Heliothis subflexa(Noctuidae) is a specialist moth whose larvae feed only on Physalis (Solanaceae). Although traditionally described as a frugivore, H. subflexa also feed on fruit that has been infected with the smaller larva of Symmetrischema lavernaella (Gelechiidae), suggesting that it may engage in omnivory. The goal of this study was to observe whether H. subflexa has a preference for infected fruits and to find out how consuming fruits occupied by S. lavernaella affects larval performance. A dual choice experiment on infected and uninfected fruits was used to determine preference. To evaluate the effects on performance, a no choice test was carried with infected and uninfected fruits diets and assimilation efficiency calculated for caterpillars in both groups. Heliothis subflexa was found to prefer infected fruits and would consume the whole fruit, including S. lavernaella. However, performance of larvae fed an infected fruit diet were significantly lower than those given multiple uninfected fruits. On these tests, H. subflexa would frequently leave S. lavernaella uneaten when fed infected fruits. While preference for infected fruit may be a response to greater palatability in fruits induced by S. lavernaella, maintenance of this preference may result from rare encounters with infected fruits across its hosts range. Overall, my results suggest H. subflexa is a facultative omnivore that may consume smaller caterpillars in its late instars.


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