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Ruspolia differens (Serville) (Orthoptera: Tettigoniidae), also known as the ‘edible grasshopper’, ‘African edible bush-cricket’, and ‘nsenene’, is regarded as one of the most promising edible insect species that can be used for food, particularly in Sub-Saharan Africa. However, there is insufficient information on suitable diets and their effects on survival, adult weight, fecundity, and developmental time of this species, which are preconditions for large-scale production. In this study, we experimentally evaluated the effects of 12 diets (wheat bran, rice seed head, finger millet seed head, soya bran, maize bran, fresh maize comb, millet flour, chicken feed egg booster, simsim cake, sorghum seed head, powdered groundnut, and germinated finger millet), that are known to be accepted by R. differens, on their growth and reproductive parameters. The survival rate, developmental time, and adult weight varied considerably on the various diets. The highest nymphal survival rates, shortest development times, and highest adult weights were recorded for both sexes when fed fresh maize comb and germinated finger millet diet. Lifetime fecundity of females fed on germinated finger millet also was, on average, more than twice higher compared to other diets. The present study demonstrated that relatively inexpensive and locally available germinated finger millet, fresh maize seed (at the silking stage on the comb), sorghum seedhead, and finger millet seedhead could be successfully used to rear and sustain populations of R. differens. Our findings contribute to the future design of an effective mass-rearing system for this economically important edible insect.

The edible katydid, Ruspolia differens (Serville), is an economically and nutritionally important insect species that is common and widespread in Africa. Currently, there are aims to develop mass-rearing methods suitable for this species, but a critical first step would require a suitable oviposition medium to ensure economic and easy production of eggs with high hatchability. The objective of the present study was to determine the oviposition preference and egg hatchability in different oviposition media. Based on preliminary testing of a wide range of different materials, two oviposition media, namely, artificial (folded plastic cloth) and natural medium (leaf sheath of Pennisetum purpureum Schumach attached to a stem), were selected for a detailed experiment. A two-choice laboratory experiment was conducted in which R. differens females were able to select between the folded plastic cloth (one side covered with short fleece) and a leaf sheath of P. purpureum (wrapped in polyester fiber). The results show that R. differens laid almost three times more eggs on the plastic cloth (mean ± SE, 169.3 ± 18.0) than on the natural substrate, P. purpurem (69.0 ± 13.9). However, the hatchability (overall mean% ± SE, 56.5 ± 4.7) of eggs in the two media did not differ. Folded plastic cloth, therefore, provided a more effective medium for egg laying by R. differens, and is thus a promising oviposition medium for getting natural populations to start laying eggs in future mass rearing.

There are increasing interests in rearing edible insects in Africa, but information on how the feeds modify their fatty acids is largely lacking. In this work, the influence of artificial diets on the fatty acid contents and composition in the edible Ruspolia differens (Serville, 1838), in Uganda was assessed. R. differens was reared on the mixtures of six gradually diversified diets of two, three, four, six, eight and nine feeds. The diets were formulated from rice seed head, finger millet seed head, wheat bran, superfeed chicken egg booster, sorghum seed head, germinated finger millet, simsim cake, crushed dog biscuit pellet and shea butter. Fatty acid methyl esters were prepared using direct transesterification method, and analysed using gas chromatography. The contents of saturated, monounsaturated and polyunsaturated fatty acid differed significantly among the diets. The more diverse diets resulted in increased content of the polyunsaturated fatty acids. The n6:n3 ratio differed significantly among the diets and between the sexes, with R. differens fed on the four-feed diet having a higher n6:n3 ratio than those fed on other diets. Also, the fatty acid composition differed significantly among the diets, and diet diversification corresponded with the proportions of polyunsaturated fatty acids, especially linoleic acid. Overall, our results demonstrate that higher levels of essential fatty acids can be achieved by rearing R. differens on highly diversified diets. These findings are important in informing the design of future mass-rearing program for this edible insect.

Ruspolia differens (Serville) (Orthoptera: Tettigoniidae) is a highly valued edible grasshopper species in Africa. However, the effects of plant diets on lipid content and fatty acid composition of R. differens are not well understood. We tested the effects of four diets on the total lipid content and fatty acid composition of R. differens. Sixth instar nymphs of R. differens were reared on one, and mixtures of two, three, and six natural plant inflorescences. Individuals collected from the field constituted a control treatment. We extracted lipids and analyzed the fatty acid methyl esters using gas chromatography–mass spectrometry. We analyzed if the total lipid content, body weight, and fatty acid composition differed among diets and between the sexes using two‐way ANOVAs and a PERMANOVA model, respectively. The total lipid content and weight of R. differens did not differ among the diets. The nine common fatty acids were palmitic (mean across treatments, 26%), oleic (22%), palmitoleic (18%), linoleic (13%), stearic (7%), myristic (6%), myristoleic (4%), α‐linolenic (2%) and arachidic acid (1%). The composition of fatty acids and the proportion of essential fatty acids significantly differed among the diets. The proportion of essential fatty acids was highest in the control treatment (21%) but low in less diversified (one to three feed) diets (12–13%). This study demonstrates that the fatty acid composition in R. differens can be influenced through diet. Thus, with dietary manipulations, using local plants in Africa, it is possible to produce R. differens with preferred high quality essential fatty acids for human consumption.

Ruspolia differens (Serville) (Orthoptera: Tettigoniidae, Conocephalinae) (its common names including ‘African edible bush‐cricket’, ‘edible grasshopper’, and ‘nsenene’) is an important source of food for humans in East Africa, but its ecology and biology are poorly understood. We explored the host plants of R. differens with a series of no‐choice and multiple‐choice laboratory experiments using 18 local common grass and sedge species in Uganda. In no‐choice experiments, the degree of acceptance differed significantly among the studied plant species, but in only three species were leaves rejected and in one species were inflorescences rejected. The pattern of acceptance among plant species was different in the local vs. swarming populations. Leaves were generally more accepted by the local population, whereas inflorescences were generally more accepted by the swarming population. Both leaves and inflorescences were more readily accepted by males than by females. According to the multiple‐choice experiments, R. differens preferred inflorescences over leaves. Our results demonstrate that R. differens is a facultatively oligophagous grass‐specialist, which has a clear preference for certain grass or sedge species (especially inflorescences), but it accepts many host plants if the preferred ones are not available. To preserve viable natural populations of R. differens in East Africa in the long term, our results draw special attention to the availability of grasslands where accepted and preferred host plants are available year‐round.

The edible grasshopper Ruspolia differens (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 sustainable mass production technique needs to be developed. Unfortunately, however, basic biological know-how on feeding habits of R. differens is poorly understood, which poses a constraint on the development of mass-rearing technology. Here, we evaluated the acceptance and feeding preference of R. differens for 16 cultivated or processed foods using no-choice and multiple-choice laboratory bioassays. The results indicated that adultR. differens can eat a wide variety of foods but does not necessarily accept all the foods equally. Furthermore, our experiments showed that R. differens has high ability to select diet among those available. The order of decreasing preference was wheat bran > germinated finger millet > rice seed head > finger 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. differens. These results show potential foods that could be utilized for developing future mass-rearing methods for R. differens.

Diet mixing is a common feeding habit among polyphagous insect herbivores and is believed to be advantageous for performance-related factors like growth, survival and oviposition. However, relatively little is known about the influence of artificial diet or their mixtures on the performance of edible insects. We examined the effects of artificial diet mixtures on the developmental and reproductive performance (survival, developmental time, fresh adult weight and female fecundity) of an edible grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae). We raised individuals from eggs and reared newly hatched nymphs to adult stage on six different dietary treatments consisting of a single diet, and mixtures of two, three, five, six and eight artificial diets. More diversified diets resulted in shorter development time and greater adult fresh weight and female fecundity compared to the single diet or less diversified diets. Even with slight diet diversification, survival to adult stage was greatly improved. Overall, these results highlight the potential of diet mixtures in achieving maximum adult weights and female fecundity and shortening development time, information which could be used when designing mass-rearing programs for this edible grasshopper.

Edible insects have been suggested as an alternative and sustainable source of fats, proteins and vitamins for humans. However, their nutritional content may largely depend on the diets offered for insects. Diet-based manipulation of fatty acids in edible insects shows promise to possibly increase their essential and long-chained polyunsaturated fatty acid content and thus further enhance human diets. We reared the edible grasshopper, Ruspolia differens, under various diets with manipulated content of fatty acids, proteins and carbohydrates. The manipulated diets dramatically altered the insects’ content and composition of fatty acids, especially the content of polyunsaturated fatty acids. Dietary fatty acids were stored largely unaltered in insects. Artificial diets with high content of linoleic, α-linolenic, eicosapentaenoic or docosahexaenoic acids, increased the content of these fatty acids in the insect tenfold. The manipulated diets also affected the omega-6/omega-3 (n-6/n-3) fatty acid ratio and developmental performance. Lack of protein and fats in the diet prolongs the development and leads to lower final weight. To achieve required n-6/n-3 ratio for human consumption and to maximise biomass gain and weight, diverse diets with a source of n-3 fatty acids and protein should be used when rearing R. differens. These results demonstrate the potential for improving human nutrition in an effective and sustainable way by producing edible insects with designed nutritional content.

The responses of Afrotropical galling insects to habitat fragmentation are poorly understood. We studied the influence of fragmentation and fragment characteristics on communities of galling insects on Neoboutonia macrocalyx trees, in six forest fragments around Kibale National Park, Uganda. Insect galls were collected from six randomly cut tips of branches from each of 10 randomly selected trees in every forest five times over a 10-month period.Atotal of 6090 individuals representing five galler species were recorded. The species richness, density and community composition of gallers were significantly different among the forests. Continuous forest areas showed similar community characteristics but some fragments were similar to continuous forests and others differed from them. None of the fragment characteristics measured (size, host-tree density, distance from continuous forest boundary and from nearest neighbour) explained differences in community measures (species richness and density) of gallers. Ou...

Increasing anthropogenic disturbance in tropical rainforests is a major challenge to biodiversity conservation. The responses of herbivorous insect communities to habitat changes are not well understood. In this study, we investigated the resilience of galling insect communities associated with Neoboutonia macrocalyx (Euphorbiaceae) trees to logging in Kibale National Park, Uganda. Resilience was measured by comparing the species density, abundance and community structure of gallers in nine differently aged successional forests with those in adjacent primary forests. Insect galls were sampled from the canopy of 10 randomly selected trees in each successional stage, five times in a 10-month period. A total of 7219 individuals representing five galler species were recorded. No significant differences were found in the species density and overall density of gallers between the regenerating and primary forests. The mean tree height was positively correlated with the overall density of gallers. The community structure of gallers differed significantly among the successional stages, but exhibited no clear directional recovery trend. In addition, remarkable seasonal variations were observed in galler communities, with peak abundance being found in the wettest months. The results of the preset study indicate that specialist galling insects whose hosts are pioneer trees can recolonize successional sites rapidly and are resilient to the effects of selective and clear-cut logging in case primary or secondary forests with an established population of Neoboutonia host trees (source populations) are close by. Thus, recovering tropical forests can provide important habitats for galling insect biodiversity, highlighting the need to include them in management and conservation priority plans.

The effects of bottom-up forces on the community structure of tropical insect gallers and within species variation in gall morphotype assemblages are not well understood. We tested the roles of increased nutritional quality and density of host plants with respect to structuring the galling insect communities and gall morphotype assemblages on Neoboutonia macrocalyx trees in Uganda. Plant nutritional quality and resource concentration were manipulated with four levels of fertilization and the group size of trees, respectively. After applying these treatments in May 2011, gallers established naturally on experimental replicates. Five months later, we sampled gallers and recorded their numbers and the different morphotypes. We analyzed the effects of treatments on the structures of galler communities and gall morphotype assemblages. We recorded 5237 individuals, representing four galler species. One species, Cecidomyiid leaf galler, was represented by three morphologically distinct galls. Fertilization, host tree density and their interactions significantly changed the structures of galler species communities and gall morphotype assemblages. The results of the present study demonstrate the important role of bottom-up factors in structuring galler communities and the gall morphotype assemblages. These changes are likely caused by differential responses of different galler species and gall morphs to plant quality or quantity changes.