Graduate Thesis Or Dissertation
 

Temperature-dependent development and field observations of some western Oregon coccinellids (Coleoptera: Coccinellidae)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/qn59q675q

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  • The recent colonization of Oregon by an exotic, intentionally introduced coccinellid, Harmonia axyridis, was the basis for lab and field research into lady beetle developmental biology and community composition. Harmonia axyridis was the dominant coccinellid in an arboreal habitat, and comprised over 70% of all lady beetles, and 82% of live coccinellid mass. The species has at least two generations per year, spring and fall. A parasitoid of coccinellids, Dinocampus coccinellae, attacks this new species at rates of less than 1%. A manipulative study focusing on the egg-development of guild members which co-occur with H. axyridis found a moderate adaptation to cool temperatures in this species. Another introduced predatory coccinellid, Coccinella septempunctata, was shown to be extremely tolerant of heat. Egg-to-adult development was found to vary significantly between three seasonal generations of H. axyridis in western Oregon. Overall, H. axyridis required 267 degree-days above a lower developmental threshold temperature of 11.2°C, and these parameters differed significantly from values reported for a population introduced into France. A study of intraspecific variation of intrinsic traits in Calvia quatuordecimguttata, a species which co-occurs with H. axyridis in Oregon, did not find differences in either lower developmental thresholds, heat-unit requirement, or pupal weight that could be correlated with elytral coloration. C. quatuordecimguttata was also found to express coloration independent of temperature experienced by immatures. However, this species as a whole was found to be extremely adapted to cold-temperatures. The lower threshold for egg-to-adult development of 8.2°C in C. quatuordecimguttata may be the lowest reported for an aphidophagous lady beetle.
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