On the significance of changes in pterothoracic sternal morphology within the Vilernae (Ommatolampinae, Acrididae)

Abstract

The Nicarchi (sensu Descamps 1976) are a group of flightless genera within the Vilernae, characterized by living on trunks of trees and by a series of mostly adaptive morphological features. They also have relatively wide thoracic sternal interspaces. It is shown here that this last is due to two processes: development of relatively wider thoraces and reduction in the size of the sternal lobes. The latter correlates with loss of flight and of the wings, as shown by a series of genera from within the Vilernae, and is associated with the atrophy and/or loss of the indirect flight musculature. A probable selective advantage of both processes is to increase the space available for the crop, the major organ of food storage and digestion.