Flow patterns around gills of pupal net-winged midges (Diptera: Blephariceridae): possible implications for respiration

Abstract

Dye studies of water flow around pupae of species of Blephariceridae show that the pupa and gills act as a "bluff body" and produce matched pairs of vortices, or regions of low pressure, downstream of the gills. Solenoidal vortices are also produced at the bases of the gills, as is reversed flow between the two gills. Bubbles of air produced from the gill plastron of live pupae are considered to be the result of decreased solubility of air in water in the low-pressure regions associated with the gills. We conclude that the pupal gills of Blephariceridae, Simuliidae, and probably other aquatic insects are designed to make use of regions of low pressure for respiratory purposes.