The effect of adult density on the reproductive output and hatching performance of the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

Commercial availability of insect biomass for food and feed calls for the methodical investigation of all the complications that can deteriorate the insect farming efficiency. An appropriate stocking density is thus instrumental for the establishment of sustainable and cost effective insect farming protocols; high densities may lead to reduced insect fitness and reproduction, while low densities will result to a proportionally lower per capita yield. The present study deals with the estimation of the optimum adult density of the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), a species with great potential as food and feed source based on its high growth performance and reproductive output. However, limited data is available so far regarding the effect of adult density on its reproductive performance. Four different adult densities, ranging from 1.1 to 8.2 cm2 per adult, were evaluated in laboratory experiments in terms of reproductive output (number of eggs) and larval emergence for a period of 45 days of continuous oviposition. According to our results, the reproduction output, expressed as the cumulative number of eggs per adult and the cumulative larval hatching rate, was not affected by the adult densities tested here. Although high hatching rates that in most of the cases exceeded 85% were observed within the initial oviposition interval, these rates were in all treatments drastically reduced to 48-56% after 30 to 36 d. High adult survival (over 93%) was observed during the trial. In this experiment, the maximum reproductive output was observed in the highest density of adults that were left to oviposit continuously for a month. Data as such provide an opportunity to further exploit A. diaperinus in high-throughput production systems.