Fig. 3. The increase in pteridine content (intensity averaged over all individuals of an age class, ± 2 s.e.m.; for N values, see Materials and methods) with known age in laboratory-reared D. serrata females (A) and males (B). Linear regressions though the average values for each sex displayed here indicated that pteridine content was closely associated with age in females (r²=0.917, F_1,16=175.8, P<0.001) and males (r²=0.760, F_1,15=47.6, P<0.001).