There are Two Kinds of Bean Beetles in this World- Those that are Easy to Catch, and Those that Aren’t: A Study of Polymorphic Traits in Callosobruchus maculatus
Dr. Brian Yurk; Dr. Aaron Putzke
When food resources, percent relative humidity, and population density are satisfactory, the bean beetle will present itself in a sexually dimorphic state referred to as the sedentary morph that renders males and females easily distinguishable. However, when food availability, humidity, and population density become environmental stressors for adult bean beetles they convert to dispersal morphology. In the dispersal morph, the males and females react by changing behavior and morphology. There has been very little study on the differences in oviposition behavior between sedentary and dispersal morphologies in the bean beetle. We designed a set of experiments to better understand how this change may affect oviposition rate, development rate, and adult longevity. We found that an increase in available substrate for egg-laying resulted in an increase in adult longevity and an increase in the fecundity of adult females. Furthermore, we found that beetles in the sedentary morph were much more likely to initiate oviposition on the first day of the experiment, while beetles in the dispersal morph were seen to delay first oviposition even into the tenth day. Lastly, we found that ovipostion rates for sedentary beetles were greatest within the first few days, laying almost all of their eggs before day five. Females in the dispersal morph laid fewer eggs, and laid almost all of their eggs between days four and five.
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