Year of Publication

2016

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department

Entomology

First Advisor

Dr. Kenneth F. Haynes

Abstract

The return of bed bugs to prominence as an urban pest has precipitated an emphatic research response from the scientific community in an effort to better understand their biology and management. However, not all aspects of bed bug biology have received equal attention. The role of symbiotic bacteria in the normal function and biology of insects is often underappreciated, and this is true of bed bugs. Bed bugs have two main endosymbiotic bacteria, a Wolbachia species and a poorly-characterized gamma-proteobacterium referred to as BLS. However, their interactions with the host are poorly understood. I explored various aspects of these symbionts and their relationship with bed bugs. Major objectives included studies of the methods for symbiont elimination to create aposymbiotic strains, modes of endosymbiont transmission within a bed bug population, and impacts of symbiont loss on the host. Additional studies of bed bugs measured the impact of juvenile hormone analogs for the control of bed bugs.

Endosymbionts often form close interdependent relationships with the host, making it difficult to create a truly aposymbiotic strain. Maintaining bed bugs at elevated temperature (36°C) for five weeks or feeding for eight weeks with the antibiotic rifamycin were determined to be the most effective methods of those examined, including the use of other antibiotics. Although these two treatments were not successful in eliminating symbionts completely from treated adults, aposymbiotic strains were successfully created by harvesting the offspring of treated bugs soon after treatment.

Transovarial transmission of endosymbionts in bed bugs is well documented, but additional methods of transmission have not been explored. The reproductive strategy exhibited by bed bugs, traumatic insemination, has been suggested as a possible avenue of horizontal transmission of symbionts. My experiments demonstrated horizontal transmission of BLS from the male to the female during mating, but there was no indication that the new infection was passed from females to males or directly to offspring. No horizontal transmission of Wolbachia was detected. There was also no evidence of transmission through coprophagy.

In contrast with normal symbiotic controls, bed bugs which lacked both symbionts took a significantly longer time to develop to the adult stage. Successive generations of aposymbiotic bugs took longer to develop, up to several months. Supplemental B Vitamins administered through blood meals did not compensate fully for the slowed development. Upon reaching the adult stage, aposymbiotic bugs were significantly smaller than normal bugs in total body length and head-capsule width. Symbiont loss did not directly affect fecundity of adults.

Hydroprene and methoprene administered as the active ingredients of formulated products produced negative effects such as reduced fecundity and increased mortality only at doses much greater than label rate, and did not inhibit feeding or activity at sub-lethal doses. This work with Juvenile Hormone analogs has been published in Pest Management Science.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2016.527

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