Nutritional profile of a novel artificial diet and the effect of photoperiod on the fitness parameters of reared Ruspolia differens

Abstract

The tettigoniid, Ruspolia differens, is a widely consumed grasshopper across Sub Sahara Africa (SSA), mainly where periodic large swarms occur during the rainy months. The present wild harvesting of this grasshopper species is not sustainable and limits the yearlong presence of these delicacies. One method to circumvent this is developing mass-rearing technologies for this nocturnal and omnivorous insect within SSA. However, to mass-rear this species on a large scale, the optimal diets and light regimes need to be established. Complete nutritional profiles of edible insect diets are rare. In our study, using a newly formulated artificial diet we assessed multiple performance traits for R. differens reared at two light regimes. A complete dark (<1 h light, 5:95 L:D) and 50% light (~12 h light, 50:50 L:D) from newly hatched nymphs to death of the adults. Proximate composition of this novel artificial diet was carbohydrates: 53.5%, crude protein: 21.0%, ash: 7.0%, fat: 5.0%, crude fibre: 4.5%. All essential amino acids and mineral elements were also present. It took on average 8-9 moults to reach adults in the light-reared insects as opposed to 6-7 moults for those reared in the dark. Adult longevity in the dark-reared insects was also significantly longer (37±3.7 days) compared to the light-reared ones (10±3 days). These findings strongly support the nocturnal behaviour of these bush crickets and suggest rearing them in a predominantly dark environment would seem a profitable venture, as fewer energy demands in terms of lighting are required. Such a diet, when fully optimised will facilitate automation and reduce labour for feeding them in mass-rearing programs.