Determining the ages of adult females of different members of the Simulium damnosum complex (Diptera: Simuliidae) by the pteridine accumulation method

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Abstract
A significant relationship between pteridine content of the head, fly age and fly size, which was independent of temperature, was found for adult females of Simulium sirbanum Vajime & Dunbar using flies maintained at different constant temperatures after eclosion. Similar relationships for flies maintained at varying temperatures within the species' natural ranges were obtained in experiments with the Beffa form of S. soubrense Vajime & Dunbar (sensu Post, 1986), S. sanctipauli Vajime & Dunbar (= S. soubrense sensu Post, 1986), S. squamosum (Enderlein), S. yahense Vajime & Dunbar and S. damnosum sensu stricto. Common slopes for the effects of age and size could be fitted to all these species. Relations between pteridine concentration in the head, fly size and age, with the common slopes but with species-specific intercepts, were used to estimate the age structure of wild-caught populations of the Beffa form of S. soubrense, S. squamosum and S. yahense. A dry season sample of S. squamosum was estimated to be older than a wet season sample. The mean age of the S. soubrense population, sampled one week after its presumptive breeding sites were treated with larvicides, was estimated to be 13.5 days. The maximum was 30.9 days and a frequency distribution of the estimates had distinct peaks, at three day intervals between 8 and 21 days. The significance of the results is discussed in relation to fly longevity and gonotrophic cycle lengths.