Unwelcome guests at farms breeding the black soldier fly, Hermetia illucens (L.) (Diptera Stratiomyidae)

Abstract

Livestock farms represent a source of attraction for other species, which find food resources on the animals themselves, in the food supplied to them, in their manure, etc. Insect farms too can suffer infestation by different organisms living on substrates or behaving as parasites and/or predators. Breeding of the black soldier fly (BSF), Hermetia illucens (L.) requires organic materials which are attractive for other arthropods (commensals, mycetophages, scavengers, etc.). During recent years, the breeding system adopted at the Di.Pro.Ve.S. of the Università Cattolica del Sacro Cuore, Piacenza (Italy), has suffered the presence of the following ‘pests’: Megaselia scalaris (Loew) (Diptera Phoridae), Muscina stabulans (Fallén) (Diptera Muscidae), Monomorium pharaonis (L.) (Hymenoptera Formicidae) and Caloglyphus berlesei (Michael) (Astigmata Acaridae). The use of fermented fruit, vegetables or of an artificial diet to induce egg laying proved to be attractive for small flies such as M. scalaris. This species also takes advantage of the aqueous sugar solution used to feed BSF adults. Infestations by M. scalaris are worrying because its larvae can compete efficiently with those of the BSF in substrate colonisation. Likewise, M. stabulans can be attracted by the substrates, even though this species has not shown the same levels of high competitiveness as the previously mentioned species. M. pharaonis was observed to prey on eggs and newborn BSF larvae. Lastly, infestations by the mite C. berlesei were detected when conditions for the larval development of the BSF were not optimal. This species could also be harmful for the workers involved in the breeding. The establishment of insect and mite populations inside BSF rearing boxes suggests that a careful analysis should be made based on the location of the breeding facility and a series of measures should of course be adopted when this kind of structure and activities are designed and realised.