Daily mean number of eggs laid by the southern cattle tick (Acari: Ixodidae) compared with mean egg mass weight.

Among several methods used to estimate the efficacy of an acaricide is the Drummond adult test, based on formulas which permit the assessment of the reproductive capacity of treated female ticks in comparison with controls. A constant value of 20,000 is normally used in these formulas, because this figure approximates the number of larvae that will hatch from 1 g of eggs. In laboratory studies conducted on large numbers of ticks, egg counting is a time-consuming and fastidious operation. Therefore, in quantitative studies, sampling techniques are more convenient. The use of the weight of egg masses laid by ixodids is adequate because eggs congregate in clusters. Experimental results have demonstrated that the analysis of the mean daily weight of egg aliquots in comparison with actual counts, from the 1st to the 20th d of oviposition, did not permit rejection of the hypothesis that 20,000 would be a representative number of eggs contained in 1 g. When aliquots were weighed only on the 20th or the 30th d of the oviposition-incubation period, and the results were analyzed in comparison with egg counts, the value of 20,000 no longer was reliable to express the number of Boophilus microplus (Canestrini) eggs contained in 1 g.