Publication Date

2025

Document Type

Dissertation/Thesis

First Advisor

King, Bethia H.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Biological Sciences

Abstract

Insects use multiple body parts, not just their mouth, to taste. Whether a particular body part has a taste function can be determined indirectly by examining the morphology or electrophysiological response of its sensilla (sense organs) or directly by the insects’ behavioral response. Understanding the taste system of insects allows development of better management strategies against pest insects and strategies to protect beneficial insects.House flies, Musca domestica L., are pests at livestock facilities. House fly numbers are controlled mainly by manure management and chemical controls. Toxic granular fly baits remain one of the most popular and effective forms of chemical control of house flies. While these baits contain a sucrose phagostimulant, some also contain the bittering agent denatonium benzoate at 20 or 100 ppm as a deterrent for humans who might accidentally consume the bait. Though house fly response to sucrose is well studied, their response to bitter compounds was unknown before my research. It is known that house flies use tarsi and mouth parts for tasting, but whether house flies can utilize other body parts for tasting was unknown. Understanding the body parts used by house flies for tasting sucrose, a phagostimulant in fly baits, and fly response to denatonium benzoate and other bitter compounds will help in developing effective chemical controls that are aversive to non-target organisms but not to the pest fly. The present study investigated the taste response of each of the three pairs of tarsi, tibiae, and femurs, as well as the antennae and wings, in house flies. This was done by measuring the proboscis extension response (PER), and in the case of the wings, also the grooming behavior. PER is a visible precursor to consumption. Both male and female house flies were able to distinguish between sucrose vs water when their fore, middle, and hind tarsi contacted the treatment solutions. The fore tibiae and femurs of females and the middle femurs of males also allowed this. Of the body parts tested, the middle, and especially the fore tarsi, were the ones most responsive to sucrose. Contact of aristae (part of the antennae) did not elicit PER regardless of whether contact was with a toothpick that had been soaked in sucrose, water, or nothing. For both males and females, neither the proportion of flies exhibiting PER nor the duration of grooming was significantly affected by whether the anterior wing margin was contacted with a toothpick that had been soaked in sucrose, water, or a dry toothpick. As the second objective of the present study, house fly behavioral response to denatonium benzoate was examined, using two different diluents, sucrose solution or orange juice. Response of flies to quinine and sucrose octaacetate, two other bittering agents, was also examined in sucrose. PER of both male and female flies was significantly reduced by addition of 1000 ppm of denatonium benzoate to sucrose. Response of males was also reduced at 100 ppm. Consumption of sucrose by both male and female flies was reduced by addition of 100, 500, and 1000 ppm of denatonium benzoate, but consumption by males was also reduced at 10 ppm. Addition of sucrose octaacetate had no detectable effect on consumption of sucrose at 100, 500, or 1000 ppm. In contrast, addition of quinine reduced consumption by both male and female flies at all tested concentrations. In orange juice, 10 ppm of denatonium benzoate is often avoided by children. With orange juice, fly PER patterns were the same for both sexes, with a reduction at 1000 ppm of denatonium benzoate. Orange juice consumption by flies was reduced significantly at 1000 ppm of denatonium benzoate for females but not at any of the concentrations tested for males. Since the laboratory reared strain of house flies showed some aversive responses to currently used concentrations of denatonium benzoate in fly baits, a similar study was conducted with three strains of house flies recently collected from dairy farms in Florida. The response of adult house flies to 10, 100 and, 1000 ppm denatonium benzoate in sucrose solution was compared to response to sucrose only solution using PER and consumption assays. Three house fly strains, DBQB, WD, and UF, each from a different Florida dairy farm, were tested within two generations of collection. Strain DBQB, but not strains WD or UF, had a known history of exposure to toxic baits containing denatonium benzoate. For males, all strains avoided PER and consumption with 1000 ppm, but not with 10 ppm. Males of WD and UF strains, but not DBQB strain showed significantly lower frequency of PER at 100 ppm. Males of WD strain, but not DBQB or UF strains, also avoided consuming 100 ppm. For females, the pattern of significance for PER was the same for all strains: avoidance for 1000 ppm but not for 10 or 100 ppm. Female consumption was significantly reduced at 1000 ppm for the DBQB and WD strains, but not for the UF strain, but no strain avoided 10 or 100 ppm for consumption. Thus, these results suggest that in some populations of house flies, 100 ppm of denatonium benzoate may reduce consumption by flies. Quinine is not a promising bittering agent to be used in fly baits, but sucrose octaacetate could be. Given that the concentration is greater than 20 ppm but less than 100 ppm, there is still an opportunity to use denatonium benzoate in fly baits, so that the targeted house flies will not depict reduced feeding behaviors. As house flies can taste with their leg parts, but not wings, or antennae, fly control measures that depend on fly contact feeding should target developing baits that would stimulate tarsal gustatory receptors and elicit fly feeding behaviors.

Extent

117 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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