Host Location by Adults and Larvae of Specialist Herbivore Heliothis Subflexa G. (Lepidoptera: Noctuidae)

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Title: Host Location by Adults and Larvae of Specialist Herbivore Heliothis Subflexa G. (Lepidoptera: Noctuidae)
Author: Benda, Nicole Denise
Advisors: Coby Schal, Committee Co-Chair
John Godwin, Committee Member
George Kennedy, Committee Member
Fred Gould, Committee Co-Chair
Abstract: Heliothis subflexa is a specialist herbivore, whose larvae feed on fruits of Physalis species (Solanaceae). Although Physalis surface extracts have been shown to elicit attraction and oviposition by adult ovipositing females, little else was known as to how adults locate their host plants for oviposition. Also, larvae are sometimes dislodged from the plant when the plant abscises the fruit they are feeding on. The ability of larvae to re-locate their host plant from the ground had not been evaluated. The purpose of this research was to evaluate the host location and oviposition behavior of H. subflexa adult females and larvae using common garden studies, behavioral assays in the lab and in the field, and direct field observations. H. subflexa showed a clear preference for some Physalis species over others in the common garden. Plant age and date also affected incidence of eggs and fruit damage on the Physalis plants. In laboratory two-choice simultaneous and sequential behavioral assays, H. subflexa showed a preference for P. philadelphica over tobacco. However, preference for Physalis was not to the complete exclusion of tobacco and a portion of eggs were placed on tobacco (˜20% on average). Field observations found that this was not a lab artifact. Females laid an average of 20% of eggs on non-hosts in the field, though most were placed very close to the plant. An evaluation of the host location ability of neonates found a high fitness cost to ovipositing on non-hosts. The ability of larger larvae (third and fifth instar) to re-locate the host plant after being dislodged from the plant via fruit abscission was affected by larval size, plant architecture, and host-specific behavior as compared to a close relative, H. virescens.
Date: 2007-03-26
Degree: PhD
Discipline: Entomology

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