Date of Award

Winter 12-14-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Entomology

Advisor

Andrei Alyokhin

Second Committee Member

Allison Gardner

Third Committee Member

Edward Bernard

Abstract

Black soldier flies (BSF), Hermetia illucens (Linnaeus) (Diptera: Stratiomyidae) consume decaying organic waste as larvae (BSFL) and can be used for recycling a variety of biogenic wastes. BSFL can also be processed into value-added animal feeds, including those used in aquaculture. An overarching goal of this project was to obtain additional insights into BSF biology to improve their rearing and handling in future mass-production facilities serving Maine aquaculture.

We tested BSFL growth in the laboratory on seven seafood wastes from Maine fish processing facilities. Substrates potentially suitable for BSFL rearing included finfish trimmings, wet sea cucumber, dry quahog, and sea urchin. Crab meal produced large larvae in short time, but larval mortality was high. There were dramatic differences in seemingly similar materials, such as wet and dry sea cucumber or wet and dry quahog, highlighting the importance of thorough testing of specific substrates instead of extrapolating from published data.

We investigated antixenotic and antibiotic effects of finfish substrate inhabited by BSFL, which are important for hygiene in mass-rearing facilities. Green blow flies, Lucilia sericata (Meigen) (Diptera: Calliphoridae), were reluctant to colonize substrates previously inhabited by BSFL even after the latter were sifted out. When released into BSFL-containing substrates, the majority of L. sericata larvae emigrated. There was significantly lower enzymatic activity as measured by fluorescein diacetate in substrate inhabited by BSFL than in the control. Subsequent plating and enumeration of colony forming units attributed that to decline in bacterial abundance. Fungal abundance were not significantly different from the control when BSFL were present but increased after their removal. BSFL also altered the taxonomic composition of microbial communities in finfish substrate, as estimated by a diversity assay using bTEFAP® illumina sequencing with 20k reads of fungal ITS and 16s primers.

Migration of BSF prepupae is commonly exploited for self-harvesting biomass in commercial rearing facilities. We tested if harvesting larvae prior to the prepupal stage can produce larger larvae than those harvested as prepupae. Our results indicated that larvae were at their highest weight immediately before transition into prepupae. Therefore, the late larval instar before reaching prepupae can be considered as the optimal harvest period for larval biomass.

BSF are normally found in subtropical and warm temperate regions. Potentially, cold temperatures can also be used to manipulate the rate of BSFL development, which may be needed for obtaining certain life stages in mass-production facilities. We determined that BSFL were highly susceptible to freezing. Chilling at above-freezing temperature also had a significant negative effect. However, it was much smaller, especially for fifth instars. We do not anticipate that BSF will become an invasive species in Maine. Low temperatures may be used to manipulate development of the late instars, but at a cost of higher mortality.

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