Alysha Soper, 2008

Luther College

The effects of the tachinid, Myiopharus infernalis, on the population dynamics of Lema daturaphila (Coleoptera: Chrysomelidae)

Recent studies conducted in northern Virginia have shown that the early season abundance of the specialist herbivore, Lema daturaphila (three-lined potato beetle), may not synchronize with the late season availability of its food resource, Physalis longifolia, due to the presence of the parasitoid fly, Myiopharus infernalis (Tachinidae: Diptera). This study set out to determine the degree to which this parasitoid influences the dynamics of the Lema population. Through a series of observational and experimental methods conducted at Blandy Experimental Farm it was found that the parasitoid’s infection rate was constant over the first 5 weeks of the summer, with its biggest impact on Lema late in the summer when it eliminated 80% of beetles that would have otherwise emerged as adults. The fates of both beetle larvae and eggs over the summer were also identified and quantified such that parasitism rates were determined for each as well life stage mortality. Throughout the summer, 72% of all Lema eggs died before becoming larvae. These results suggest that the parasitoid is not the major limiting factor on the beetle population. Future research on egg mortality, or the survival and fecundity of adult beetles might start to fill in the gaps about the life cycle of Lema daturaphila


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