Opening mechanism of the mouth of the hematophagous hemipteran, Triatoma infestans

A morphological study of the tips of the stylets in an haematophagous hemipteran has been performed with a scanning microscope in order to determine both the relative positions of the mouthparts during a meal, and the means by which the ‘functional mouth’ can open. If the stylets of Triatoma are examined following severance of the labium, differences in the morphology and relative position of the two maxillary tips are observed. When, prior to a meal, the insect explores the medium with its mouthparts, the tips of its maxillary stylet are united. By contrast, when the bug is pumping food the left stylet is retracted relative to the right stylet and its tip is bent outwards.We have studied the mechanics of the system which allows the tip of the left maxillary to rock, resulting in the opening of the alimentary canal. Finally, we have re-examined the stylet movements of dissected animals in the light of these new morphological findings.