STUDIES ON THE FUNCTIONAL ANATOMY OF THE INTESTINES OF HETEROPTERA

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Abstract
Recent studies on the physiology of the malpighian tubules of insects have indicated that they play only a minor role in osmotic regulation. The major part of this function is now thought to be performed by glandular structures in the hind‐gut. The Heteroptera are of especial interest from this viewpoint, since they are a group in which a wide range of food choice occurs, so that species can be found which are adapted to either extreme of osmotic stress, from dry seed diets to the water superfluity of sap sucking. A comparative study of intestinal anatomy and histology was undertaken, in the hope that correlations between structure and dietary water content would be revealed, and in particular to elucidate the mechanism of water disposal in the sap‐sucking forms (which lack the specialized filter chamber of Homoptera). The first part of this paper describes the results of this study, and a case is made out for the interpretation of the gastric caeca possessed by sap‐sucking species as water excretory organs. In the second part, the phenomenon of intestinal discontinuity is shown to be widespread among the most specialized sap‐sucking Heteroptera, and its relationship to the water excretion theory of gastric caeca is discussed.