Studies on the excreta of a grasshopper (Melanoplus bivittatus

THE methods hitherto employed in the study of the gross metabolism of insects have been based mainly on the changes in their content of physiologically important substances during development, and on the ability of the organism to grow on selected diets of known composition. There is a third method, extensively employed by mammalian physiologists, namely analysis of excreta; this, as Uvarov (1928) has pointed out, necessarily involves its correlation with the constitution of the food. Very few analyses of insect excreta, however, have been made, and those of any completeness are confined to species of unusually specialized food habits, i.e. the clothes moth (Babcock, 1912), (Hollande & Cordebard, 1926), and Rhodniusprolixus (Wigglesworth, 1931). The insect selected for this study was the grasshopper, Melanoplus bivittatus Say, an unspecialized phytophagous type, morphologically rather primitive; the diet used throughout the experiment consisted of head lettuce alone, with distilled water ad lib. 5000 individuals were raised from egg to adult on this diet, their excreta being frequently collected, freed of fragments of food and exuviae, an