Efforts to promote sustainable production and processing of Ruspolia differens Serville (Orthoptera: Tettigoniidae) as a viable agribusiness model for enhancing food and nutrition security have gained momentum. However, the inexistence of rearing techniques adapted to this insect creates uncertainty regarding the effectiveness of up-scaling production. This study evaluated the effect of five temperatures (26, 28, 30, 32 and 34 °C) on egg development time, percentage hatchability and nymphal weight at hatching. It also evaluated the average weekly wet weight attained by R. differens and percentage survival during growth when reared at 30 °C on four different food plant diets. The diets composed of (1) star grass Cynodon dactylon (L.) Pers.; (2) wild millet Eleusine indica (L.) Gaertn.; (3) guinea grass Panicum maximum Jacq.; and (4) a mixture of the three food plants. The highest hatchability (89.33±3.06%) was observed for egg clusters that were not detached from the leaf sheaths and incubated at 30 °C. At the same temperature, the hatchability of eggs detached from the leaf sheath was 43.33±4.16%. The wet nymphal weight at hatching varied significantly across the different incubation temperatures. For eggs that were not detached from the leaf sheath, it ranged between 3.12±1.20 mg at 30 °C to 4.15±0.98 mg at 34 °C, while for eggs that were detached, it ranged between 2.96±1.14 at 32 °C to 6.0±2.0 mg at 26 °C. The highest wet nymphal weight (586.4 mg) and growth rate (10.47 mg/day) of adult R. differens after 8 weeks was recorded on wild millet, followed by the mixture of the three food plants (553.7 mg; 9.9 mg/day). Food plants significantly influenced survival of nymphs, with C. dactylon and P. maximum associated with the highest survival rate (53.3%). These findings are central to upscaling R. differens production.
The increasing demand for animal protein in sub-Saharan Africa has led to insects being considered an alternative protein source for food and feed. In Uganda, chicken mash, containing fish meal as the protein source is commonly used to rear crickets. However, fishmeal is an expensive protein source that is also human food. This study therefore aimed at establishing an alternative preferred (consumed in the highest quantity) plant leaf diet for raising the Modicogryllus conspersus cricket, and the most suitable temperature for hatchability and egg development. The effect of (a) three diets (cassava leaves + cocoyam leaves + milk weed leaves; cassava leaves + pumpkin leaves + wandering Jew; and cassava leaves + lablab + Cinderella weed) on growth; and (b) incubation temperature (26, 28, 30, 32, and 34 °C) on egg hatchability and egg development time were studied. Cassava, pumpkin and milk weed leaves were the most ‘preferred’ of the tested plant leaves. Egg development time was longer at lower temperatures, ranging between 7-14 days across a 26-34 °C temperature range. The highest hatchability (95%) was observed at 28 °C, below and above which hatchability decreased. The maximum nymph weight (1.58 mg) at hatching was observed at 26 °C and decreased with increasing egg incubation temperature. The plant leaf diet containing leaves with highest protein content (pumpkin, wandering Jew and cassava) led to the highest growth and growth rate comparable to the control diet (broiler chick mash). Temperature had a significant effect on egg development time (P<0.001) and nymph weight at hatching (P<0.001) while the food type significantly influenced growth (P<0.001) and moulting time. The possibility of formulating a nutrient balanced, cost-effective, compound feed for cricket production should be investigated.
Ruspolia differens (Serville) (Orthoptera: Tettigoniidae) is a delicacy in many African countries. It is commonly mass-harvested from the wild using light traps consisting of energy-intensive mercury bulbs which pollute the environment when poorly disposed. The catch is collected using open-ended drums which are inefficient in retaining the insects. The drums also collect nontarget insects including those that produce toxic chemicals (such as pederin) that cause severe burns to human skin. To prevent escape of trapped R. differens, trappers apply potentially hazardous substances like waste cooking oil on the walls of drums. Here, we modified the collection drum by fitting a funnel to retain R. differens; and partitioned it into three compartments with wire meshes of variable sizes to filter nontarget insects. Additionally, we replaced mercury bulbs with light-emitting diode (LED) bulbs which are energy-efficient. We evaluated the performance of the modified R. differens trap (modified drums and LED bulbs) compared to the current collection drums and mercury bulbs. The catch of R. differens in the modified drums was comparable to that of current drums. Nontarget insects were significantly filtered from the catch collected in modified drums compared to the current drums. Further, LED bulbs of 400 W trapped a comparable quantity of R. differens as 400 W mercury bulbs, but with less than half the consumption of electricity compared to the mercury bulbs. We concluded that modified R. differens light traps have better energy-use efficiency and ensure safety to collectors, processors, and consumers.
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