Bioassays for the optimization of Hermetia illucens (L.) egg laying in a prototype of industrial plant

The black soldier fly Hermetia illucens (L.) (Diptera: Stratiomyidae) presents a particular interest for the feed and food industry as its larvae have the capacity to convert quickly and efficiently large quantities of organic waste or byproducts into a protein biomass rich in fats. Although the information on larvae development is abundant, the necessary knowledge of adult biology to produce large amounts of eggs remains a great challenge. This work represents a part of a regional project (ValoriBio, Emilia Romagna, Italy) where one of the main outputs is the construction of a pilot plant for H. illucens mass rearing, which includes a module for adult rearing. Therefore, a specific custom-made climatic chamber was developed and it consisted in a thermally insulated container (1m3 volume), with a transparent window bearing a light-emitting diode (LED) lights source (UV, green and blue LEDs) on top. Temperature and humidity were controlled through a Peltier cooler/heater system, an ultrasound humidifier and several humidity-temperature digital sensors. An exterior electronic board connected to a touch screen was developed to control and record the rearing parameters. The biological parameters used to establish the functionality of the prototype were the patterns of oviposition, the egg weight and adult longevity. Bioassays were conducted in tree types of climatic chambers at 27°C ± 0,5°C and 70 ± 5% relative humidity considering as treatments the use of different light sources (fluorescent tubes, white LEDs and the UV-green-blue combination of LEDs) and the flies diet (water and sugar, just water or nothing). The results allowed to identify the better conditions to obtain the highest amounts of eggs in the shortest time.