Fig. 5

Discrimination of Anopheles gambiae mosquitoes by age. Two groups (a and b) of Anopheles gambiae s.s (Kisumu strain) specimens of different ages were killed by freezing before REIMS analysis. Mosquitoes were raised on sugar solution, regardless of age. Differences between age groups were explored by PC-LDA and visualised using OMB (i) as well as R, in form of 3D models (using different linear discriminant combinations) (ii) and kernel density plots for each LD. The difference between classes in model a (built with 100 PCs in OMB and R) is only 24 h; nonetheless, a distinct group formation can be observed with chronological positioning within the 3D space, leading to a transition from younger to older samples. Model b (built with 88 PCs in OMB and 85 PCs in R), comprising young and old mosquitoes (2 groups each), revealed greater variance between the young classes than between the old. Sample numbers per class, model a: 0–1 day (n = 47), 2 days (n = 84), 3 days (n = 39), 4 days (n = 27), 5 days (n = 30); model: 0 days (n = 17), 1–2 days (n = 29), 12 days (n = 46), 13 days (n = 83)