Publication Date


Document Type


First Advisor

King, Bethia H.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


The effects of RMR (resting metabolic rate) and environment on tonic immobility were examined in the parasitoid wasp Spalangia cameroni (Order Hymenoptera: Family Pteromalidae). Tonic immobility (TI) is described as a state that an organism enters wherein they fall onto their back or side and become immobile for a period of time when disturbed. This state can last for several seconds to a few hours, depending on the organism in question. The organism may be aware during this period of time but unable to move. Female wasps were subjected to experimental treatments that involved manipulation of their environment, specifically, cold versus room temperature, access to food versus not, presence of 5 additional conspecifics versus absence of conspecifics, and access versus lack of access to cover. Then whether there was a correlation between the duration of TI and resting metabolic rate was determined. A higher resting metabolic rate may be negatively correlated with the duration of TI, as more energetic individuals may rely on escaping a predator rather than displaying TI. In addition, the transition from high metabolic to TI may be more difficult, e.g., more time consuming, than from a low metabolic rate to TI . Resting metabolic rate was measured with a simple-to-make respirometer. The results of this study suggest that being alone versus with conspecifics and lack of access to cover are associated with an increase in the duration of TI and a decrease in the latency to TI. Only lack of access to cover was associated with a greater proportion of individuals exhibiting TI. Cold had no significant effect on any of the three measures of tonic immobility. There also was no correlation between the resting metabolic rate of the wasps and their duration of tonic immobility. How these results compare to results in other species is discussed.


45 pages




Northern Illinois University

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