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Table 6 Predictions of male An. gambiae age-grade as a function of their morphology, as obtained from the optimally performing breakpoints model. Text indicates whether males of a particular trait combination would be classified as being ≤ 4 days old (YOUNG), or older (OLD). Numbers in parentheses give the probability of males with a particular trait combination being in the 'OLD' age group, with the model categorizing all males with a probability of lower < 0.5 as being 'YOUNG', and 0.5 ≥ as being 'OLD'. Following this classification guide, the age status of 'YOUNG' and 'OLD' male An. gambiae should be correctly predicted on 81% and 95% of occasions respectively.

From: A reliable morphological method to assess the age of male Anopheles gambiae

Proportion of testis occupied by sperm reservoir Age class as predicted by the optimal model (BREAKPOINTS)
  Clear area absent Clear area present
≤ 30% YOUNG (0.26) YOUNG (0.04)
31%–60% YOUNG (0.31) YOUNG (0.05)
61%–90% OLD (0.93) OLD (0.62)
> 91% OLD (0.98) OLD (0.98)