4.1. Insect Breeding

Mealworms (TM) are the larval form of the mealworm beetle, Tenebrio molitor, a species of darkling beetle. Darkling beetle is the common name of the large family of beetles Tenebrionidae. In nature, it lives where it is dark, warm, humid, and there are lots of decaying organic matter, i.e., under decaying pieces of bark of deciduous trees. Moreover, Tenebrio molitor is a pest of grain, flour, and food stores [69]. The life cycle of Tenebrio molitor is of variable length, from 280 to 630 days. Larvae hatch after 10–12 days (at 18–20 °C) and become mature after a variable number of stages (8 to 20), typically after 3–4 months, but the larva stage can last up to 18 months. Mealworms have short life cycles, and are easy to breed [69].

Superworms (ZM), Morio worms, or Zophobas, Zophobas morio (Fabricius, 1776) (Coleoptera: Tenebrionidae) are a globally recognized feed for reptiles. In the wild, superworms larvae occur in dead (diseased) trees, where they feed on this wood. It is a popular food insect due to its ease of breeding and nutrition. Recent research efforts indicate that this insect could also be used as a partial replacement of fishmeal for farmed tilapia [70]. The life cycle of Z. morio is like other beetles, as it has an egg, larva, pupa, and adult stage. Larvae are similar to mealworm larvae, although they are much larger and more fat.

Insects for described research were purchased at a local terrarium store (Wrocław, Poland). The feeding medium for the insect larvae consisted of 100% blue corn flour (BC) or potato starch (PS). Rearing of larvae was carried out in plastic containers (in triplicate for each of the food variants) at 26 °C for 10 days. For 500 g of insect biomass, 500 g of blue corn flour (BC) and potato starch (PS) were added, respectively. After 5 days, another 200 g of feed was added.

At the end of the ten-day growth period, the larvae were separated from the feeding media by manual sieving and immediately preserved by freezing at −28 °C. The larvae were weighed about 1 g into separate glass screw-cap containers and stored at −28 °C until analysis. The mean larval weight for mealworms was 0.13 g and for superworms was 0.51 g. The larvae were baked whole and were crushed before SPME analysis.