Food ingestion and digestive enzymes in larval Aedes aegypti and Ae. albopictus (Diptera: Culicidae).

Frequency of the labral brush movements of first, second, and fourth instars of Aedes aegypti (L.) and Aedes albopictus (Skuse) was studied comparatively in the laboratory. A frequency of 197 strokes per min for the first and second instars was observed in the former species compared to 118 strokes per min in the latter species. A faster ingestion rate of algal cells also was observed in first and second instars of Ae. aegypti (mean 57.5 cells per s) compared with first and second instars of Ae. albopictus (mean 22.4 cells per s). The digestive enzymes chymotrypsin (EC 3.4.21.1) and trypsin (EC 3.4.21.4) were more active in the peritrophic membrane (including food contents) than in the midgut epithelium of both species. Chymotrypsin activity in 11-d-old third and fourth instars of Ae. albopictus was 28 times higher than in the corresponding stadia of Ae. aegypti, indicating that the former species may have a superior enzymatic process for digesting food proteins.