Browsing by Author "Roininen, Heikki"

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    Diet acceptance and preference of the edible grasshopper Ruspolia diferens (Orthoptera: Tettigoniidae)
    (The Japanese Society of Applied Entomology and Zoology, 2018-02-23)  Malinga, Geofrey M.; Valtonen, Anu;  Lehtovaara, Vilma J.; Rutaro, Karlmax; Opoke, Robert; Nyeko, Philip; Roininen, Heikki
    The edible grasshopper Ruspolia diferens (Orthoptera: Tettigoniidae) gathered seasonally from the wild is a highly valued and an economically important edible insect, particularly in East Africa. To reduce the pressure on wild populations, a sus tainable mass production technique needs to be developed. Unfortunately, however, basic biological know-how on feeding habits of R. diferens is poorly understood, which poses a constraint on the development of mass-rearing technology. Here, we evaluated the acceptance and feeding preference of R. diferens for 16 cultivated or processed foods using no-choice and multiple-choice laboratory bioassays. The results indicated that adult R. diferens can eat a wide variety of foods but does not necessarily accept all the foods equally. Furthermore, our experiments showed that R. diferens has high ability to select diet among those available. The order of decreasing preference was wheat bran > germinated fnger millet > rice seed head > fnger millet seed head > chicken feed egg booster > sorghum seed head. Finally, our study indicated that sex and color morph are not associated with the order of acceptance and preference of diets in R. diferens. These results show potential foods that could be utilized for developing future mass-rearing methods for R. diferens.
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    Performance of the African edible bush-cricket, Ruspolia differens, on single and mixed diets containing inflorescences of their host plant species
    (Entomologia experimentalis et applicata, special issue: insect production, 2020) Malinga, Geoffrey M.; Valtonen, Anu; Hiltunen, Minna; Lehtovaara, Vilma J.; Nyeko, Philip; Roininen, Heikki
    The African edible bush-cricket, Ruspolia differens (Serville) (Orthoptera: Tettigoniidae), is an eco nomically valuable insect in sub-Saharan Africa. For its mass-rearing, suitable diets that can sustain its performance need to be identified. This study aimed at finding inflorescence diets of 10 host plant species and their mixtures that result in the highest R. differens production. We reared newly hatched nymphs to adults on inflorescences of single host species, and also on a gradient of five diversifying dietary mixtures consisting of one and mixtures of two, three, five, and seven host plant species. For the single host-plant diets, the developmental time was shortest on Pennisetum purpureum, Chloris gayana, and Brachiaria ruziziensis (approximately 63 days), whereas the fresh weight was highest on B. ruziziensis and P. purpureum (approximately 0.383 g). Survival was highest (>65%) on C. gayana, P. purpureum, B. ruziziensis, Setaria sphacelata, and Sporobolus pyramidalis, and lowest on Panicum maximum, Hyparrhenia rufa, Cynodon dactylon, and Paspalum scrobiculatum (<40%). With respect to diet mixtures, the developmental time was significantly shorter (on average 16 days shorter), and survival was higher, in the most diversified diets compared to the least diversified diets. The contents of polyunsaturated fatty acids and fatty acid composition did not differ significantly among the diets. However, the content of monounsaturated fatty acids differed significantly among the diets and there was a significant diet*sex interaction. From the applied point of view, based on our results, for maximal weight and survival plus fast development, we recommend rearing on P. purpureum, C. gayana, B. ruziziensis, and S. sphacelata, and on dietary mixtures of inflorescences. These findings are important in designing large-scale rearing programs for this species.