Literature on grasshopper control published hetween 1930 and 1942 stressed the desirability of applying poisoned bait when grasshoppers begin their first main feeding period of the day. Such pubiications include those by Parker (1930). Parker, Walton, and Shotwell (1932), Criddle (1932). Ruggles and Aamodt (1938), and Bird (1940). Parker (1930) found that the lesser migratory grasshopper, Melanoplus mexicanus mexicanus (Sauss.), fed sparingly on baits at air temperatures between 55°F. and 63°F., more actively between 64°F. and 67°F., and most actively between 68°F. and 78°F. A rapid decrease in feeding occurred when air temperature rose above 80°F. or the soil surface temperature above 113°F. Much the same relationship held also for the clear-winged grasshopper, Cammula pellucida (Scudd.). On the basis of such observations it was decided chat an air temperature of 68°F. might be classed as optimum for beginning the application of bait. Parker did not, however, indicate the degree of mortality resulting from such feeding; the other writers gave no experimental data.