No abstract

iMelanoplzrs mexicanzrs mexicanus (Sauss.), from time of hatching, was fed on wheat (Renown) grown in nutrient solutions of varying nitrogen content. Some wheat was produced with an average nitrogen content of 6.16% (dry weight), some with 4.29Yq, and some with 3.33%. Survival and development were greatest on the high nitrogen wheat, least on the low. On the low nitrogen wheat no individuals developed beyond the last nymphal instar. Neither weight of adults nor the sex ratio was affected by the various foods. Females fed on wheat with a high nitrogen content laid more eggs but the viability of the eggs was not affected.

It has been demonstrated that changes in the composition of a plant influence the insects that feed upon the plant (Lipke and Fraenkel, 1956). The quantitative composition of plants can be changed by the use of fertilizers (Mulder, 1950; Rennie, 1956), and populations of insects feeding on the plants may increase or decrease (Daniels, 1957; Adkisson, 1958; Joyce, 1958). These changes in numbers of insects have been attributed to such factors as changes in nitrogen, protein, and carbohydrate content (Evans, 1938; Fritzsche et al., 1957) or various mineral constituents (Creighton, 1938).

No abstract

The long-held belief that grasshoppers are to a large extent omnivorous and, as Wolcott (1936) states, “like cows, feed on any kind of vegetation”, is slowly giving place to the view that they are much more restricted feeders. Their habit of nibbling at almost anything, particularly when they are present in large numbers, probably led to this erroneous concept. More recent work such as that of Rubtzov (1931), Criddle (1933), and Isely (1938, 1944, 1916) stresses the fact that many species of grasshopper confine their feeding to a group of related plants, and a few species to a single plant.