The behaviour of Rhodnius prolixus (Stål) during the imaginal ecdysis

Abstract

The behaviours during the imaginal ecdysis in Rhodnius prolixus (Stål) have been distinguished into three phases. The first phase is characterized by cessation of locomotion coupled with activity of localized regions such as the head or legs (rubbing and wiping). During the second (preecdysial) phase, behaviours such as rubbing and wiping continue with the addition of bursts of locomotor activity and head bobbing. In the third (ecdysial) phase, physical emergence from the exuviae occurs. The three phases differ in their degree of stereotyping. All behaviours which commence after the onset of air swallowing (late preecdysis) are stereotyped both in performance and in the sequence in which they occur. Prior to air swallowing the individual behaviours are stereotyped in performance but not in sequence. Argument is presented that the second and third phases are each initiated by a separate "decision." The first "decision" probably results from sensory information gained during the performance of the first phase and determines competence to proceed with the preecdysial phase. The second "decision" irreversibly commits Rhodnius to the ecdysial attempt and is made during the preecdysial phase prior to the onset of air swallowing. The second "decision" may evoke the stereotyped behavioural sequence observed throughout the ecdysial phase.