Hy]pera postica was first observed in Delaware on April 17, 1952, and has since spread rapidly throughout the State. It passes the winter in the adult, egg and, possibly, in the larval stage. Unusual weather in 1953 encouraged earlier spring-activity, but the peak of larval population occurred somewhat later than in 1954. The first new adults are produced in April; they continue to appear until late fall. Over-wintered adults were still present in small numbers toward the close of the season. Dispersal of adults to young alfalfa (less than 1-year-old) occurred from June on. Prior to that time, the weevil and its injury were absent from such plantings in 1953 but, in 1954, did occur in one case where conditions were favorable for early-spring invasion. More suitable conditions in young fields throughout summer and fall, irrespective of cutting dates, favored the expression of a 2nd generation, comprising possibly 2 broods; whereas older fields appeared to be less likely to sustain any pronounced new generation. The pest was not generally destruction in Delaware until the 1954 season. Heaviest damage was evident on the first growth in May, and was usually confined to fields 2 or more years old that previously had been infested. An early-spring application of dieldrin in 1953 gave satisfactory protection to the first growth. Control with this material and with heptachlor on the first growth was also effective in the 1954 experimental plots. No treatment was necessary on the 2nd growth. Yields were substantially higher in plots where control was attained. No important insect parasites were reared in Delawate from any stage of the weevil, and no predators were observed. In 1953, a fungus. Beauveria globulifera, caused heavy mortality under field conditions and in the laboratory where preliminary tests showed that it can be 100% effective. The same fungus was relatively unimportant in 1954.