Larve di Hermetia illucens allevate su substrati agroalimentari: valutazione dei tassi di crescita e riduzione degli scarti. ​

This study has tested the growth rates of Hermetia illucens on various discards from local industries in Piedmont. The waste used were: egg, threshers, dried borlanda, yeast, whey, pulp, juices, mix of pulp and juices, rice husk and silvery film. Each diet also contained water. Six vessels (replicates) were considered for each experimental diet and the test started by distributing 100 larvae at six days of life for each vessel over 200 grams of substrate. To observe the growth rate of larvae, thirty specimens were weighed every four days. For each replica, 23 pupae were selected, closed inside transparent perforated trays, and transferred to the insect room, where they followed their natural metamorphosis until the flicker. The flies were then weighed and subjected to sex control, and, after death, the following operations were repeated. The data collected were analyzed using the statistical software IBM SPSS (P<0.05). Statistical analysis showed a similar effect of the D4 and D6 diets in terms of larval growth, as larval weights were almost overlapping. In contrast, the D2 larvae had significantly lower weights than the D4 and D6 diets. This is the result of a particularly liquid consistency of the D2 diet, so the larvae tended to escape, showing a rather poor level of adaptation. The larvae of this diet, in fact, struggled to gain weight, and, consequently, the larva-pupa time has lengthened remarkably compared to the other two diets. The pupae of the D2 diet had, moreover, a greater weight than the other two, due, reasonably, to the greater time spent by the larvae in the substratum, which has allowed to accumulate more nutrients for the stage of pupation. The flies in this diet, therefore, have recorded a greater weight and lifespan than the D6 diet. With regard to sex, the analysis showed that females had a greater weight than males; however, the latter showed a longer survival time. For the pupa-fly interval, on the contrary, there were no differences between males and females, analogous to the weight of the exuviae. In general, the present study has shown that Hermetia illiucens is highly adaptable to various substrates, but has shown that, in addition to the chemical properties of the substrate, physical properties should also be taken into account, in this case the water retention capacity of the ingredients. In fact, the D2 diet has led the larvae to a poor adaptability, pushing them to want to escape from the tank and making the following diet the least performing in terms of larval growth. At the same time, however, the insect has shown the ability to complete its cycle for all diets considered. The studies conducted on Hermetia illucens bred on food waste have a literature certainly wide. The main doubts and curiosities were widely investigated, often with more than positive results. This confirms the applicability of the use of the insect as a resource of the circular economy and makes insects a possible source of protein for farm animals, so demand is growing and available sources scarce. The present study confirms what has already been extensively investigated, namely the strong adaptability of this insect (Hermetia illucens), and properties of bioconverter.