A COMPARATIVE STUDY OF THE PROVENTRICULUS OF ORTHOPTEROID INSECTS WITH REFERENCE TO ITS USE IN TAXONOMY

Abstract

The structure of the proventriculus in 115 species of orthopteroid insects (eight orders) is investigated.The Blattodea, Mantodea, and Isoptera have a conical proventriculus, with 6 or 12 longitudinal teeth. There are eight tubular gastric caeca. The Ensifera (Grylloidea and Tettigonioidea) have a globular proventriculus with a tubular neck. In the globular part are six longitudinal folds each bearing a series of appendages and separated from one another by partitions. There are two bulbous gastric caeca. The four families of the Caelifera have a tubular proventriculus. The Acrididae have six longitudinal plates in the proventriculus and six gastric caeca with anterior and posterior projections. The other three families have no plates in the proventriculus. The Tridactylidae have two gastric caeca, the Tetrigidae have six short, conical caeca, and the Cylindrachaetidae have six long, tubular caeca.The Phasmida have a tubular proventriculus with longitudinal, spine-bearing folds and a long flaplike oesophageal valve. In the Grylloblattaria the organ is globular with 12 longitudinal folds in the intima, and two ranks of 12 pyramidal teeth at its posterior end. The Dermaptera have a tubular proventriculus, flared slightly where it joins the crop. Internally there are six longitudinal folds bearing small scalelike projections, and a cushion of bristles at the anterior end of each fold. In the Plecoptera the proventriculus is tubular, with 14 longitudinal, spine-bearing plates on its inner surface. There are seven tubular gastric caeca.A 'phylogenetic tree' demonstrates the relationships of the groups studied, and a systematic key is prepared.