Rachel Moran

Publication Date


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First Advisor

Ende, Carl von

Degree Name

B.S. (Bachelor of Science)

Legacy Department

Department of Biological Sciences


The larval stage of the phantom midge Chaoborus americanus (Chaoboridae) is an important predator on zooplankton in temperate, fish less ponds. Chaoborus have distinct development stages typical of holometabolous insects: egg, larva (four larval instars), pupa, and adult. Temperature and food levels can significantly affect development rates in insects. The purpose of this study was: (1) to compare developmental patterns of populations of C. americanus from different latitudes (northern Wisconsin, northern Illinois), which experience different annual temperature regimes; and (2) to construct a mathematical model to predict larval development patterns (Developmental Model) and another to predict abundance patterns for C. americanus populations based on temperature and food regimes (Abundance Model). The Chaoborus americanus population in northern Wisconsin (Tender Bog) completed one generation per year. The northern Illinois population (Meiner Pond) had two to three generations per year. Pupae that developed from overwintering fourth larvae in Meiner Pond were nearly twice the mass of the pupae in the summer generation. The pupae of the overwintering population of fourth instar larvae in Tender Bog were comparable in mass to the pupae from the first generation (late May) in Meiner Pond. Using laboratory estimates for growth and development rates, and the appropriate field temperature data, the Developmental Model correctly predicted a one-year generation time for a C. american us population in Tender Bog and three generations per year for the Meiner population. Similarly, the results generated by the abundance model were consistent with the phenology and patterns of instar abundance observed in the respective populations.


25 pages




Northern Illinois University

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