Nervous control of the mechanical properties of the abdominal wall at feeding in Rhodnius.

Recent work has shown that the mechanical properties of insect cuticle can change suddenly (Cottrell, 1962; Bennet-Clark, 1962). In the larva of Rhodnius it was found that the abdominal endocuticle rapidly becomes extensible when the insect starts to feed (Bennet-Clark, 1962); the abdomen can then expand greatly to accommodate the large meal of blood. Bennet-Clark suggested that this plasticization of the cuticle is to be attributed to the appearance in the haemolymph of some factor absorbed from the blood meal through the gut wall. Cottrell (1962) showed that the process of expansion of the newly emerged adult CalUphora, which involved a similar increase in extensibility of certain parts of the cuticle, was under nervous control. Later work on Rhodnius has shown that the properties of the abdominal cuticle in this insect can also be affected by the nervous system (Maddrell, 1962; Nunez, 1963 a, b). This paper is an attempt to reconcile the various findings of work on Rhodnius and to describe more fully the way in which the mechanical properties of the abdominal cuticle are controlled in Rhodnius.