EMERGENCE PATTERNS OF DELIA-RADICUM (DIPTERA, ANTHOMYIIDAE) POPULATIONS FROM NORTH-CAROLINA AND NEW-YORK

Cabbage maggot, Delia radicum (L.), populations from North Carolina (F letcher and Scaly Mountain) and New York (Geneva and Highland) were su rveyed to detect differences in the emergence pattern of flies from ov erwintered pupae. Populations from all locations consisted of differen t proportions of early- and later-emerging individuals. However, popul ations from New York consisted predominately of early-emerging individ uals (greater-than-or-equal-to 90%), whereas populations from North Ca rolina were composed of a higher percentage of later-emerging individu als. Emergence patterns of F, progeny from crosses between early- and later-emerging flies from Scaly Mountain demonstrated that emergence t raits were genetically controlled. D. radicum phenology studies in Nor th Carolina suggested that temporal isolation of the two types was hal ted by an extended period of aestivation during the summer months, whi ch subsequently allowed the two populations to interbreed during the a utumn months. The relative proportion of early:late emergers appears t o be unstable over time, which may be due to differential mortality fa ctors operating when populations are temporally isolated or due to dom inance or recessive factors governing earliness or lateness, or both.