John A. Joyce

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

Abstract The black soldier fly, Hermetia 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.

Selected Life-History Traits of Black Soldier Flies (Diptera: Stratiomyidae) Reared on Three Artificial Diets

Abstract Hermetia illucens (L.) was reared on three larval diets to determine their effects on preimaginal development and selected adult life-history traits. Prepupal and adult characteristics were examined for individuals reared on each diet and compared with field-collected prepupae and corresponding emergent adults. Diet did not significantly influence development or survivorship to the prepupal stage. However, adult emergence for all diets was significantly less than that determined for the wild population. Development time from egg to adult for individuals reared on the diets at 27°C ranged from 40 to 43 d with the larval stage lasting 22–24 d. We observed >96% larval survivorship to the prepupal stage and 21–27% adult emergence. Females accounted for 55–60% of emergent adults across treatments. Specimens reared on each diet were reduced in size, longevity, and calorie content in comparison to specimens from the wild population. Males within diet treatments and field-collected specimens were significantly smaller than females and emerged 1–2 d before females. Additionally, males reared on the diets and provided water lived for 9 d, whereas females lived for 8 d. This information indicates the diets might be used for rearing soldier flies. However, further refinement is needed to produce adults similar to those found in nature.

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.

Evaluation of Body Conformation, Composition, and Density as Traits for Indirect Selection for Dress-out Percentage of Channel Catfish

Abstract Channel catfish, Ictalurus punctatus, were processed and carcass traits such as head length, head width, body depth, girth, lipid percentage, head percentage, viscera percentage, specific gravity and body density evaluated as predictors and alternative traits for indirect selection of dressing percentage in live fish. Age, size, and sex had influence on the importance of these variables for predicting dressing percentage. Viscera percentage had the greatest phenotypic association with dressing percentage. No traits that could be measured from live fish were found that would predict viscera percentage. Body density had phenotypic correlations of -0.64 and -0.61 with dressing percentage in females and males, respectively, and was the best measurement for predicting dressing percentage in live catfish.

Susceptibility of Black Soldier Fly (Diptera: Stratiomyidae) Larvae and Adults to Four Insecticides

Abstract Dosage-mortality regressions were determined for black soldier fly, Hermetia illucens (L.), larvae fed cyromazine or pyriproxifen treated media. Cyromazine LC50s 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 λ-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.

Influence of Brood Fish Size on the Breeding Performance of Channel Catfish

Abstract Influence of the size of 5-year old brood channel catfish (Ictalurus punctatus) on spawning success, spawn weight, hatchability, swim-up interval, and growth of fry and fingerlings were investigated in a 2-year study. Brood fish that differed in body weight by one standard deviation were classified into three size-classes, large (LG), medium (M), and small (S). Brooders were pair-mated in individual pens and egg masses were artificially incubated. Fry and fingerlings hatched from individual egg masses were reared together as sibling groups in indoor tanks for 40 weeks. Mathematical relationships between parental size catfish and the traits of their offspring were determined by regression analysis. Chi-square analysis indicated that the size of the pair-mated brood fish was associated with spawning success. An increase of 1 kg (2.2 lbs) in body weight of male brooders was associated with a decrease of 15-21% in spawning success. Female size-classes significantly influenced spawn weight and number ...

Persistency of Hot Brands and Their Effects on Growth and Survival of Fingerling Channel Catfish

Abstract Fingerling channel catfish (Ictalurus punctatus) were hot branded at 20 and 30 weeks of age (mean weights, 6.7 and 26.5 g, respectively). Of the fish branded at 20 weeks of age, 97% retained readable brands for 20 weeks; of those branded at 30 weeks, 96% retained readable brands for 18 weeks. When the fingerlings of each group were compared with unbranded controls at 54 weeks of age, no significant differences were found in percent survival. At this age, the fingerlings branded at 20 weeks weighed significantly less than did the controls. No difference was found between fingerlings branded at 30 weeks and their controls. Channel catfish reared in warm-water, high-density culture systems should probably be branded no earlier than 30 weeks (or a mean weight of about 27 g). They should be rebranded no later than 16 weeks after the initial branding.

Comparison between sequential and concurrent matings of two females and one male channel catfish, Ictalurus punctatus, in spawning pens

Abstract In selective breeding of channel catfish, it is desirable to mate, in the same breeding season, each one of a large number of males to more than one female. This experiment compared sequential and concurrent matings of two females and one male in 36 individual spawning pens. The number of females that spawned in the former group was higher (74%) than in the latter (57%); the numbers of males spawning in each group were similar (135 vs 130%, respectively). These differences are associated with (1) a higher female mortality in concurrent (30%) than sequential matings (3%), and (2) a smaller difference in frequencies of double-spawning males (40 vs 47%, respectively). It was concluded that neither the sequential nor concurrent methods tested could satisfy the needs of selective breeding, even though the former method was closer to this objective.