Insulin-like immunoreactivity and molting in Rhodnius prolixus

Two prominent cells were observed when fifth stage Rhodnius female larval brains were stained with anti-insulin serum. The staining intensity of these cells varied during the instar, being lowest on Day 1 and Days 5 and 6 after feeding. Injection of anti-insulin serum into 5th stage larvae immediately after feeding and on Days 4 and 5 in females and on Days 5 and 6 in males prevented molting. Control antiserum had no effect on the molting process. Injections at other times during the instar had no effect unless serum was injected just prior to ecdysis. Control or anti-insulin serum injected at this time disrupted normal ecdysis. These results are discussed in terms of the control of the developmental program of the insect.