POPULATION-GENETICS AND GENE VARIATION IN PRIMARY AND SECONDARY SCREWWORM (DIPTERA, CALLIPHORIDAE)

Allozyme variation in screwworm, Cochliomyia hominivorax (Coquerel), a nd secondary screwworm, C. macellaria (F.), populations from northwest Costa Rica was examined. Variability was observed in 11 of 13 enzyme loci and frequency of the most common allele was <0.95 for 5 loci in s crewworm. In secondary screwworm, 12 of 13 loci were variable and the frequency of the most common allele was <0.95 for 6 loci. Expected het erozygosities were 0.149 and 0.160 for screwworm and secondary screwwo rm, respectively. Goodness-of-fit statistics for Hardy-Weinberg equili brium and Wrights F statistics indicated that both species are panmict ic with no evidence of population substructuring. Nei's genetic distan ces were 0.000-0.001 for intraspecific comparisons and 0.899-0.916 for interspecific comparisons. The data indicate a high level of gene flo w between populations within each species.