THE CUTICULAR PATTERN IN AN INSECT, RHODNIUS PROLIXUS STAL

1. The cuticle on the abdominal tergites of Rhodnius larvae has a uniform pattern of stellate pleats. In the adult this pattern is replaced by an oriented one of transverse ridges resembling greatly elongated pleats. 2. Neither pattern results from the disposition of cells each with the potentiality for forming only part of it. The simplicity of the patterns suggests some simple mechanical cause operating over a large area. 3. The effect upon the adult of altering the orientation and relative position of pieces of larval integument has been used to study the mechanism of orientation of the pattern. 4. The orientation of the adult pattern is mediated through the epithelium, since rotation of the larval integument causes corresponding disturbances in the adult pattern. 5. The epithelium has a capacity for maintaining transverse continuity within similar levels in the axis. There is an axial gradient within each segment, the anterior showing greatest facility in maintaining continuity. 6. Pieces of transplanted integument unable to restore their continuity with the whole animal show a concentric pattern of ridges, as if the capacity for continuity had been satisfied by each level joining up with itself. 7. Such isolated pieces of integument moult but fail to grow normally, suggesting that continuity in the axial gradient of the whole animal is necessary for the quantitative control of growth. 8. Pieces of integument from different axial levels within a segment when juxtaposed influence the direction of displacement of the pattern according to their level. A transplant from the anterior stimulates the host ridges to maintain continuity posterior to it, and conversely.