Dirty Defense: Investigating the Defensive Function of Fecal Egg Cases in the Dogbane Beetle (Chrysochus auratus)
Location
Sydnor Performance Hall, Schewel Hall
Access Type
Campus Access Only
Presentation Type
Oral presentation
Entry Number
96
Start Date
4-16-2026 10:45 AM
End Date
4-16-2026 11:00 AM
School
School of Medicine and Health Sciences
Department
Biology
Keywords
dogbane beetle, dogbane, fecal, feces, protection, egg
Abstract
Instances of fecal matter being used as a defensive strategy have been documented in various insect species. For example, some beetle larvae construct fecal shields to protect them from predators. Female dogbane beetles (Chyrsochus auratus) construct fecal cases in which they enclose their eggs, but it is unclear why. These fecal egg cases are typically laid on the underside of leaves of spreading dogbane, Apocynum androsaemifolium. I investigated whether the fecal egg cases produced by dogbane beetles reduce egg mortality and whether oviposition on the underside of leaves provides protection from desiccation and natural enemies. Field observations and experiments were conducted from mid-June through late July 2025 at the University of Lynchburg Claytor Nature Center in Bedford County, Virginia. Observational data were collected on egg case abundance and spatial position on individual host plants. Two manipulative experiments were performed: 1) an experiment in which leaves with fecal egg cases were flipped over to expose the intact cases to the sun and 2) an experiment in which fecal egg cases were flipped over on the undersides of leaves to expose the eggs to predation. I predicted that there would be higher egg mortality in eggs exposed to the sun and in eggs exposed to predation. Results from the leaf flip experiment were not statistically significant (p>0.05). There was no difference in mortality between eggs in fecal cases on leaves facing the sun and those in the natural ground-facing position. Data from the fecal egg case flip experiment were statistically significant (p< 0.05). Specifically, exposed eggs were more likely to be depredated and fail to hatch than unexposed eggs.
Primary Faculty Mentor(s)
Dr. John Styrsky
Primary Faculty Mentor(s) Department
Biology
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Dirty Defense: Investigating the Defensive Function of Fecal Egg Cases in the Dogbane Beetle (Chrysochus auratus)
Sydnor Performance Hall, Schewel Hall
Instances of fecal matter being used as a defensive strategy have been documented in various insect species. For example, some beetle larvae construct fecal shields to protect them from predators. Female dogbane beetles (Chyrsochus auratus) construct fecal cases in which they enclose their eggs, but it is unclear why. These fecal egg cases are typically laid on the underside of leaves of spreading dogbane, Apocynum androsaemifolium. I investigated whether the fecal egg cases produced by dogbane beetles reduce egg mortality and whether oviposition on the underside of leaves provides protection from desiccation and natural enemies. Field observations and experiments were conducted from mid-June through late July 2025 at the University of Lynchburg Claytor Nature Center in Bedford County, Virginia. Observational data were collected on egg case abundance and spatial position on individual host plants. Two manipulative experiments were performed: 1) an experiment in which leaves with fecal egg cases were flipped over to expose the intact cases to the sun and 2) an experiment in which fecal egg cases were flipped over on the undersides of leaves to expose the eggs to predation. I predicted that there would be higher egg mortality in eggs exposed to the sun and in eggs exposed to predation. Results from the leaf flip experiment were not statistically significant (p>0.05). There was no difference in mortality between eggs in fecal cases on leaves facing the sun and those in the natural ground-facing position. Data from the fecal egg case flip experiment were statistically significant (p< 0.05). Specifically, exposed eggs were more likely to be depredated and fail to hatch than unexposed eggs.