Black soldier fly (Diptera: Stratiomyidae) colonization of pig carrion in south Georgia.

The black soldier fly, Hermetia illucens (L.), is thought to colonize corpses 20-30 days postmortem. However, recent observations indicate this might not be true for all cases. Therefore, we conducted a study examining colonization by the black soldier fly and other Diptera on pig carrion in a plowed field in southern Georgia from 20 September through 21 February. Our data indicate black soldier flies could colonize a corpse within the first week after death. Knowing this information could prevent a serious mistake in estimating the time at which a corpse is colonized by this species. This study also represents the first record of Chrysomya rufifacies in Georgia.

Rearing methods for the black soldier fly (Diptera: Stratiomyidae).

The black soldier fly, Heretia illucens (L.), is a nonpest tropical and warm-temperate region insect that is useful for managing large concentrations of animal manure and other biosolids. Manure management relying on wild fly oviposition has been successful in several studies. However, confidence in this robust natural system was low and biological studies were hampered by the lack of a dependable source of eggs and larvae. Larvae had been reared easily by earlier investigators, but achieving mating had been problematic. We achieved mating reliably in a 2 by 2 by 4-m screen cage in a 7 by 9 by 5-m greenhouse where sunlight and adequate space for aerial mating were available. Mating occurred during the shortest days of winter if the sun was not obscured by clouds. Adults were provided with water, but no food was required. Techniques for egg collection and larval rearing are given. Larvae were fed a moist mixture of wheat bran, corn meal, and alfalfa meal. This culture has been maintained for 3 yr. Maintainance of a black soldier fly laboratory colony will allow for development of manure management systems in fully enclosed animal housing and in colder regions.

Susceptibility of black soldier fly (Diptera: Stratiomyidae) larvae and adults to four insecticides.

Dosage-mortality regressions were determined for black soldier fly, Hermetia illucens (L.), larvae fed cyromazine or pyriproxifen treated media. Cyromazine LC50 for larvae dying before becoming prepupae ranged from 0.25 to 0.28 ppm with dosage-mortality regression slopes between 5.79 and 12.04. Cyromazine LC50s for larvae dying before emergence ranged from 0.13 to 0.19 ppm with dosage-mortality regression slopes between 3.94 and 7.69. Pyriproxifen dosage-mortality regressions were not generated for larvae failing to become prepupae since <32% mortality was recorded at the highest concentration of 1,857 ppm. LC50s for larvae failing to become adults ranged from 0.10 to 0.12 ppm with dosage mortality-regression slopes between 1.67 and 2.32. Lambda-cyhalothrin and permethrin dosage-mortality regressions were determined for wild adult black soldier flies and house flies, Musca domestica L., and for susceptible house flies. Our results indicate that the wild house fly, unlike the black soldier fly, population was highly resistant to each of these pyrethroids. Regression slopes for black soldier flies exposed to lambda-cyhalothrin were twice as steep as those determined for the wild house fly strain. Accordingly, LC50s for the black soldier fly and susceptible house fly were 10- to 30-fold lower than those determined for wild house flies. The differential sensitivity between wild black soldier flies and house flies might be due to behavioral differences. Adult house flies usually remain in animal facilities with the possibility of every adult receiving pesticide exposure, while black soldier fly adults are typically present only during emergence and oviposition thereby limiting their exposure.

Genetics and fitness costs of cyromazine resistance in the house fly (Diptera: Muscidae).

The genetic basis of cyromazine resistance was investigated in the house fly, Musca domestica L. The ED-R strain, which was collected in Mississippi and selected further in the laboratory, was 116.5-fold resistant compared with the laboratory susceptible strain, OR-S. The SEL strain, which was created by crossing ED-R with OR-S followed by three cycles of reselection and backcrossing to OR-S, was 84.7-fold resistant relative to the susceptible strain. Mortality data from reciprocal crosses of resistant and susceptible flies indicated that resistance was autosomal and not influenced by maternal effects. The relative position of probit lines from the parental strains and reciprocal crosses showed that resistance was expressed as an incompletely dominant trait with D = 0.30 and 0.32 for ED-R and SEL, respectively. To determine the number of genes involved, models of one, two, three, four, and five loci were used to compare observed and expected mortality of F1ED-R x susceptible backcross. Resistance was best described by a polygenic model of three loci when equal and additive effects of loci were assumed. Another approach, which was based on phenotypic variances, showed that nE, or the minimum number of freely segregating genetic factors for ED-R, equaled 3.07. ED-R showed greater reductions in fitness compared with SEL independent of the presence or absence of sublethal concentrations of cyromazine. These data suggested that reduced fitness was not due to deleterious pleiotropic effects of the resistance genes themselves but arose from other loci in the ED-R genotype.