Causes of Rapid Carrion Beetle (Coleoptera: Silphidae) Death in Flooded Pitfall Traps, Response to Soil Flooding, Immersion Tolerance, and Swimming Behavior


Terrestrial insects in water can often delay or escape drowning by floating and swimming. However, we observed that flooding of pitfall traps baited with rotting carrion results in high overnight mortality of captured beetles and reasoned that this risk may be enhanced by microbial respiration. By assessing carrion beetle (Coleoptera: Silphidae) response to flooding, tolerance to immersion, and swimming behavior, we offer insights to this cause of death and beetle behavioral physiology. Response of buried Nicrophorus orbicollis Say to soil flooding resulted in beetles moving to the soil surface. The lethal time to 50% mortality (LT50 (immersion); mean ± 95% CI) for Nicrophorus investigator Zetterstedt, Nicrophorus marginatus F., Necrodes surinamensis F., and Thanatophilus lapponicus Herbst was 14.8 ± 2.3, 9.0 ± 3.3, 3.2 ± 1.1, and 12.1 ± 2.5 h, respectively. Swimming behavior and survival time of N. investigator was tested using yeast:sucrose (Y:S) solutions to create a eutrophic, severely hypoxic aqueous environment. LT50 (swimming) for N. investigator was 7.5 ± 1.4, 6.0 ± 1.7, and 4.2 ± 1.2 h for the low, medium, and high Y:S solutions, respectively, and  >24.0 h in control treatments. Nicrophorus investigator survived nearly twice as long when completely immersed in deoxygenated water, as might occur in flooded burrows, than when swimming on the surface. We document for the first time, the rapid induction of hypoxic coma and death for a terrestrial insect from enhanced microbial activity and CO2 production of an aqueous environment, as well as suggestions on trapping protocols related to the federally endangered Nicrophorus americanus Olivier.



Document Type





Animals, Coleoptera, Ecology, Entomology, Floods, Longevity, Nebraska, Oklahoma, Saskatchewan, Soil, Species Specificity, Swimming

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Journal Title

Environmental entomology