Host plants of the non‐swarming edible bush cricket Ruspolia differens

Abstract

The edible Ruspolia differens (Orthoptera: Tettigoniidae) is a widely‐consumed insect in East Africa but surprisingly little is known of its host plant use in the field. We studied host plants used by non‐swarming R. differens for 15 months, in central Uganda. In particular, we assessed the use of host plant species with respect to host cover in the field and host parts used by R. differens , also recording their sex, developmental stages, and colour morph. Ruspolia differens were found on 19 grass and two sedge species and they were observed predominantly (99% of 20,915 observations) on seven grasses (namely, Panicum maximum , Brachiaria ruziziensis , Chloris gayana , Hyparrhenia rufa , Cynodon dactylon , Sporobolus pyramidalis , and Pennisetum purpureum ). Ruspolia differens was most frequently observed on the most common grass of each study site but P. maximum , and S. pyramidalis were used more frequently than expected from their cover in the field. Furthermore, R. differens were observed predominantly on inflorescences (97% of feeding observations) and much less frequently on the leaves (3.0%), stems (0.1%), and inflorescence stalks (0.1%) of grasses and sedges. Host use was not independent of sex, developmental stage, or colour morph. Panicum maximum was the preferred host of the youngest nymphs of R. differens . Overall, our findings indicate that a continuous supply of diverse grass resources with inflorescences is necessary for the management and conservation of wild populations of R. differens .

Performance of the African edible bush‐cricket, Ruspolia differens, on single and mixed diets containing inflorescences of their host plant species

“…Stapf (all Poaceae). All these species are known host plants of R. differens at our study location in Uganda (Opoke et al, 2019). In experiment 1, the diet treatments represented these 10 host plant species.…”

“…In experiment 2, diet treatments represented a gradient of five diversifying dietary mixtures of host plant species ranging from one to mixtures of two, three, five, and seven species (Table 1). The plant selection in experiment 2 was based on our earlier survey of potential food plants of R. differens used in the field in Uganda (Opoke et al, 2019). The gradient represents the hierarchy of use, whereby B. ruziziensis was the most used and B. ruziziensis and P. maximum were the two most used host plants in the field, respectively.…”

“…It is a multivoltine species which has distinct non‐swarming and swarming phases, with swarms occurring in East Africa during rainy seasons in November–December and April–May (Bailey & McCrae, 1978). The species is a facultatively oligophagous grass specialist, accepting and feeding on a wide range of grasses and some sedge species (Swaine, 1964; Bailey & McCrae, 1978; Valtonen et al, 2018; Opoke et al, 2019). In the field, R. differens was observed most frequently on the most common grass of each study site, with Panicum maximum Jacq.…”

“…In the field, R. differens was observed most frequently on the most common grass of each study site, with Panicum maximum Jacq. (Poaceae) being the preferred host of the youngest nymphs (Opoke et al, 2019). At present, communities collect these insects through wild harvesting which is seasonal and very unpredictable (Okia et al, 2017).…”

Growth performance and feed conversion of Ruspolia differens on plant‐based by‐product diets

“…The design of appropriate feeds is one of the key issues in developing mass‐rearing methods for this species. In the wild, R. differens is a selective grass‐feeder, preferring inflorescences over leaves (Opoke et al, 2019). In the laboratory, it accepts, for example, wheat, finger millet, rice, chicken feed, and sorghum, as well as many East‐African grasses (Lehtovaara et al, 2017; Valtonen et al, 2018; Malinga et al, 2018a,b).…”