D3151: Reproductive niche of the black soldier fly, Hermetia illucens, expands as flies age

According to Shelford’s Law of Tolerance, each organism is only able to reproduce optimally within a complex set of environmental conditions. For the black soldier fly, Hermetia illucens, although these optima are generally known, their interactions are not due to the reductive nature of experimentation. Therefore, the reproductive niche of the black soldier fly was modeled using zero-inflated regressions in multi-dimensional parameter space. The effects of environmental covariates on reproductive success (mating, oviposition, egg weight, hatch) were considered simultaneously, as was their interaction with cohort demography (age-distribution, sex-ratio, sex-specific mortality).

In zero-inflated models, data are divided into sub-models: the first representing the probability of a reproductive event occurring, and the second predicting factors which increase its probability. For the black soldier fly, this is biologically relevant because not all individuals successfully reproduce, and those that do, often do so at differential rates.

Results: Qualitative analysis of model behavior indicates cohorts of young flies (initially 1-4 d-old) are more selective about the conditions under which they will reproduce compared to cohorts which contain old flies (initially 1-16 d-old); but when they do reproduce, they do so more frequently. Most interestingly, the models also predict the highest level of mating to occur in conditions which parallel those of their native Neotropical environment, despite never intentionally subjecting the flies to these conditions. These findings are important for those considering how methods for industrial production can be modified for this species. Future research aims to improve the training data set, to model cage-level processes.