ABSTRACT
In an earlier paper (Wigglesworth, 1933b) it was shown that the cuticle of the mosquito larva Aedes aegypti (= argenteus) is permeable to water only at the anal papillae, and that water is taken in continuously by these organs and excreted by the Malpighian tubules; observations which were confirmed by Pagast (1936). But a more important function of the anal papillae has recently been made clear by Koch (1938), who has shown that in larvae of Chironomus and Culex they absorb chloride ions. They are able to take up chloride from very dilute solutions (0·001 M) and behave in this respect like the skin of frogs and other fresh-water animals as demonstrated by Krogh (1937).
Marshall and Staley (1937) accord this insect specific rank under the name of Culex molestus Eorskal.
The Copenhagen tap water is a very hard water with a chloride content equivalent to 0·006 % NaCl.
The anal and ventral papillae of chironomids also vary in size with the water in which the larvae occur, but the conditions which determine these changes are not yet very well defined (Lenz, 1930).
These tropical species were examined during a visit to the Medical Research Institute, Kuala Lumpur, F.M.S., in 1934.
