1. The mating system of Mediterranean fruit flies (Ceratitis capitata,
Diptera: Tephritidae), is based on male leks that form on the foliage
of trees, Following observations that not all males participate in le
ks, the hypotheses that (a) small males are absent from leks and (b) m
ales with inadequate nutrient reserves are unable to participate in le
ks were examined. 2. The size and weight of lekking males (n = 183) an
d resting males captured at the same time in the vicinity of leks (n =
148) were established. In addition, using biochemical techniques, the
amounts of sugar, glycogen, lipid and protein in each individual were
established quantitatively. 3. There was no significant size differen
ce between lekking and resting males. However, lekking males were sign
ificantly heavier and contained significantly more Sugars and protein
than resting males. 4. In conclusion, leks are exclusive, and only mal
es with adequate nutritional reserves may join. Thus, in this species,
reproductive success is closely linked to foraging success.