Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Scott Kight

Committee Member

Paul Bologna

Committee Member

John Smallwood

Abstract

The horned passalus, Odontotaenius disjunctus, are subsocial beetles that inhabit and defend decaying wood where they create galleries to live, mate, breed and provide brood care. The species is well known for their stridulations, making up to 14 different sounds, having one of the greatest repertoire of sounds for any known arthropod. Typically living in family units, it has been found that several families can inhabit the same log, therefore, the horned passalus can come into contact with both kin and non-kin. It is currently unknown whether the horned passalus can distinguish between nestmates and non-nestmates. Additionally, it is unknown if their stridulations, especially the most common, “disturbance stridulation” is a form of communication, and whether stridulation would differ between nestmates and non-nestmates. Because multiple family units can co-exist in the same log and still defend against intruders, it is expected that the horned passalus are able to distinguish between individuals and behave differently according to kinship and or previous experience with a conspecific. In this study, the ability of the horned passalus to distinguish between individuals, specifically between familiar and unfamiliar conspecifics, was measured by determining if there are any changes in the frequency and duration of specific behaviors when encountering a familiar vs. unfamiliar conspecific. Beetles were exposed to both familiar and unfamiliar conspecifics and the frequency and duration of the behaviors including locomotion, burrowing, stasis, stridulation, close proximity and physical contact were analyzed. No significant differences were found for burrowing, stasis or stridulation behaviors. However, beetles in isolation exhibited a significantly greater number of bouts of locomotion and spent more time in locomotion than when they were paired with another beetle (both familiar and unfamiliar treatments). Subjects tested with unfamiliar individuals tended to spend more time in close proximity and in physical contact than when paired with familiar individuals, although these differences did not reach statistical significance. These patterns suggest that the horned passalus may be capable of establishing familiarity and distinguishing between individuals, although further work is needed to confirm this. Overall, the findings of this study provide suggestive evidence that the horned passalus may display individual discrimination through changes in behavior, offering insight into interactions among members of the same family unit, other family units within the same log, and potential intruders.

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