Cornops aquaticum is a widely distributed semiaquatic grasshopper in the Neotropics. The development, feeding and oviposition of C. aquaticum take place on Pontederiaceae, especially on species of Eichhornia. Several aspects of the feeding of C. aquaticum are studied because is one of the most important herbivores of the highly invasive floating Eichhornia crassipes in native areas. The aims of this paper were:(1) to quantify the amount of E. crassipes consumed by C. aquaticum, (2) to determine the growth rate and the conversion efficiency of food ingested by this grasshopper, and (3) to determine the possible effect of consumption on E. crassipes productivity. Thirty individuals from each specific age class were used in the experiment: nymphs A, nymphs B, adult males and adult females. Insects were individually confined in plastic pots with a leaf of E. crassipes. We estimated feeding by individual, consumption index (CI), relative growth rate (GR) and efficiency of conversion of ingested food to body substance (ECI). The impact of C. aquaticum consumption on E. crassipes floating meadows was assessed with the abundance of the grasshopper, and the available data on primary production of the host plant at the study site. Food intake of C. aquaticum was 11.23% of plant productivity. Food consumption, growth rate and food conversion efficiency of this grasshopper varied according to the specific age classes. Damage caused by C. aquaticum is high in comparison with the damage caused by other semiaquatic and grassland grasshoppers, however it is not enough to prevent the growth and coverage of native E. crassipes floating meadows because abundance of grasshoppers are realtively low and the growth rate and productivity of the host plant is high. Rev. Biol. Trop. 59 (3):

We assessed the damage produced by invertebrate herbivores per leaf lamina and per m2 of populations floating-leaf macrophytes of Neotropical wetlands in the growth and decay periods, and assessed if the damage produced by the herbivores should be taken into account in the estimations of plant biomass of these macrophytes or not. The biomass removed per lamina and per m2 was higher during the growth period than in decay period in Nymphoides indica and Hydrocleys nymphoides, while Nymphaea prolifera had low values of herbivory in growth period. During decay period this plant is only present as vegetative propagules. According to the values of biomass removed per m2 of N. indica, underestimation up to 17.69% should be produced in cases that herbivory do not should be taking account to evaluate these plant parameters on this macrophyte. Therefore, for the study of biomass and productivity in the study area, we suggest the use of corrected lamina biomass after estimating the biomass removed by herbivores on N. indica. The values of damage in N. indica emphasize the importance of this macrophyte as a food resource for invertebrate herbivores in the trophic networks of the Neotropical wetlands.

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the semiaquatic grasshopper Cornops aquaticum Bruner, which is highly specific of Eichhornia crassipes (Pontederiaceae), constitutes one of the most abundant herbivores in the neotropical wetlands and a possible biological control agent of this weed in south africa. the aims of this study were 1) to assess the performance of each age category of C. aquaticum on crop plants and the host plant E. crassipes; 2) to assess the feeding preference of this grasshopper on crop plants in the presence and absence of E. crassipes; and 3) to determine the presence of nymphs and adults of this grasshopper on crops and in the adjacent wetlands where Eichhornia plants are present. Crop plants included in this study were Zea mays, Oryza sativa, Saccharum officinarum and Ilex paraguariensis. the age categories of C. aquaticum population were nymphs a (instar i and ii), nymphs B (instar iii to Vi) and adults (females and males). to assess grasshopper performance on E. crassipes and crop plants, survival and oviposition were recorded during the no-choice tests. to evaluate feeding preference, choice tests with crop plants in the presence and absence of E. crassipes were performed. abundance of C. aquaticum in the crop patches and the wetlands vegetation was assessed using an entomological net. during the no-choice tests, high survival of most C. aquaticum individuals was observed on Z. mays and E. crassipes, except for nymphs a fed on Z. mays. Ovipositions were registered in E. crassipes, Z. mays and S. officinarum, but only eggs laid in E. crassipes were endophytic and viable. C. aquaticum showed high preference to E. crassipes, whereas Z. mays and S. officinarum were the preferred plants in the choice test without E. crassipes. We did not find C. aquaticum individuals in the crop patches of Z. mays, O. sativa and S. officinarum, whereas abundance of this grasshopper varied between 28 and 62 individuals captured per minute on Eichhornia floating meadows near these cultivated areas. Our results confirm the high specificity of C. aquaticum to E. crassipes because eggs laid on crop plants are not viable and nymphs a have no possibilities of surviving when fed on these plants. Finally, we recommend carrying out choice tests and field samplings throughout the whole native range of C. aquaticum.