Semester of Graduation

Fall 2022

Degree

Master of Science (MS)

Department

Entomology

Document Type

Thesis

Abstract

The Formosan subterranean termite, Coptotermes formosanus, is a eusocial insect and an invasive urban pest. Colonies function through a division of labor among castes (i.e., queens and kings, workers, and soldiers). Though soldiers are energetically expensive to maintain, C. formosanus has a relatively large soldier caste (~10% of the colony). Soldiers are physically unable to collect food or build tunnels but are regularly found with foraging workers. In some species, soldiers influence the worker foraging behavior. In C. formosanus, aside from defense, the roles soldiers play remains unknown. In this study, we determined if soldiers influence the exploratory foraging of workers in C. formosanus. Groups of workers were introduced to planar foraging arenas to forage with different soldier concentrations. There was no significant difference in tunnel length, tunnel complexity, or food consumption within four days between foraging groups with 100 workers and 0, 2, 10, or 30 soldiers. Based on this study, no relationship was found between worker exploratory foraging activity and soldier presence. C. formosanus soldiers, like some other termite species, produce a defensive secretion for chemical defense. C. formosanus defensive secretion composition was previously investigated, showing lignoceric acid and hexacosanoic acid as two major components, but no behavioral influence was investigated. Choice assays showed C. formosanus workers were repelled by lignoceric acid, hexacosanoic acid, a mixture of lignoceric and hexacosanoic acids, and the crude extract of the soldier defensive secretion. Workers consumed less paper treated with the mix of lignoceric and hexacosanoic acid, indicating that the soldier defensive secretion may elicit repellant behavior in workers, allowing workers to escape from a potential threat. We additionally analyzed cuticular hydrocarbons (CHCs) from workers and soldiers to examine differences that may identify a soldier- or worker-specific compound. No qualitative difference was detected in CHC profiles between workers and soldiers, but of the 15 peaks identified, 13 differed significantly in relative abundance. These differences may enable colony members to distinguish between workers and soldiers, but further behavioral tests are required. By investigating the multifunctional roles of soldiers in termite colonies, this study helps better understand the complex nature of communication in social insects.

Date

11-3-2022

Committee Chair

Dr. Qian Sun

DOI

10.31390/gradschool_theses.5685

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