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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Jonathan Lundgren


The symbiotic bacteria found in the guts of insects influence many aspects of insect biology and behavior. These symbionts contribute to dietary consumption and selection, thus expanding the dietary breadth of their insect host. I assessed the ability of the facultative symbiont Enterococcus faecalis to increase seed consumption of Harpalus pensylvanicus. This was tested through antibiotic and E. faecalis inoculation treatments, after which seed consumption was measured. The results of this experiment demonstrated that a gut microbial community dominated by E. faecalis facilitated seed consumption by H. pensylvanicus. Next I examined the influence that gut symbionts have on insect dietary selection. This was accomplished by measuring seed and egg consumption of the cricket Gryllus pennsylvanicus with eliminated or intact gut microbiota. The results showed that gut microbiota caused a sex-specific dietary selection in G. pennsylvanicus. The results of these two experiments led me to investigate the forces within a habitat that could potentially manipulate the insect gut microbiota. I assessed the influences that habitat diversity has on the diversity of symbiotic gut bacteria inside the guts of insects from those habitats. The gut microbial diversity of insects found in habitats with varying levels of biodiversity were sampled. From these samples I observed that increasing biodiversity within a habitat can increase gut microbial diversity. The results obtained from all of these experiments showed that gut symbionts can affect what diet is selected, how much of a particular diet is consumed, and that habitat diversity can affect insect gut microbial diversity. These experiments demonstrate the importance of gut symbionts to their insect hosts, as well as the potential services provided by the insects.

Library of Congress Subject Headings

Microbial ecology
Host-bacteria relationships


Includes bibliographical references



Number of Pages



South Dakota State University


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