PTERIN QUANTITY AND GONOTROPHIC STAGE AS INDICATORS OF AGE IN MUSCA-AUTUMNALIS (DIPTERA, MUSCIDAE)

Spectrofluorimetric methods were used to measure pterin quantities in the head capsules of adult face flies, Musca autumnalis De Geer. Quant ities at eclosion were greater in males than in females, and were prop ortional to the head capsule width in each sex. Pterin accumulated as a linear function of time at constant temperature, at rates of 3.8 rel ative fluorescence units per degree-day in males and 1.68 units in fem ales, both above a common base of 9.8 degrees C. A mark-release-recapt ure experiment revealed that pterin accumulated at a rate of 6.40 unit s per degree-day among males, twice as fast as in the laboratory. In c ontrast, accumulation among females was 1.35 units per degree-day, app roximating their laboratory rate. Gonotrophic age grading of recapture d females indicated median development rates corresponded with expecta tions based on earlier laboratory studies, but substantial variation a mong females led to imprecise estimates of chronological age. Calibrat ion curves for each sex are presented to estimate degree-day age from head capsule width and pterin content. The pterin age-grading method a llows the study of longevity of male face flies, and complements gonot rophic methods for the study of longevity and reproductive success of females.