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A genetic study of the development of Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae): Ecological, evolutionary, and forensic importance of the secondary screwworm

NCJ Number
Date Published
114 pages

This study of Cochliomyia macellaria (blow flies) provides valuable information regarding the evolutionary biology and ecology of the species and contributes to basic knowledge of decomposition ecology.


This study found that Cochliomyia macellaria (blow flies) harbor considerable genetic variation for development time, are more likely to be faster developing in the wild, and that alleles that slow development alter correlations among life history traits in a temperature dependent manner. This study of the natural variation in blow fly biology provides valuable information regarding the evolutionary biology and ecology of the species. The selected lines provide the basic material to conduct further genetic studies to identify markers associated with variation in development time that could be used to improve accuracy in estimating ages of immature secondary screwworms for forensic purposes. Studies of this organism contribute to basic knowledge of decomposition ecology. To evaluate genetic variation in immature development rates of this species, an artificial selection experiment was performed on three Texas populations. After 23 generations of selection at 25°C, all experimental populations selected for faster development exhibited approximately a 1.5 days decrease in mean development times as compared to the founding generation, while those bred for slow development required another 3.5 days of development. The six selected lines were subsequently reared in different thermal environments to evaluate their phenotypic plasticity in development time, pupal mass, and immature viability. Under different thermal exposures, C. macellaria developed slower at cooler temperatures and faster at warmer temperatures with a difference between selection groups of approximately 3.7 days at 30°C, 5.6 days at 25°C, and 7.9 days at 20°C. Slow developers reared at 25°C and 30°C had significantly heavier pupal mass than the cooler and slower selected lines. Immature viability also differed between selection regimes, with survival to adulthood ranging from 54.8-86.7% for all blow flies studied here. Significantly higher lethality was observed in the slow developing blow flies, especially at cooler temperatures. 

Date Published: January 1, 2015