The Weevil Rostrum (Coleoptera: Curculionoidea): Internal Structure and Evolutionary Trends

Abstract

ABSTRACT The current classification of weevils has witnessed vast improvements at higher phylogenetic levels, though much remains unstable at the lower levels. In order to develop a more robust morphological character system for cladistic analysis of the higher lineages and to gain a comprehensive understanding of the structure of a hallmark feature of weevils, a comparative study was conducted of rostra throughout Curculionoidea. Semithin sections were made of the rostra of 36 exemplar genera representing all seven currently recognized weevil families, as well as 19 of 21 subfamilies within the largest family, Curculionidae, and internal structures were examined for phylogenetically informative characters. While the morphological diversity of rostral forms is impressive, general trends are apparent with respect to life-history traits and modes of feeding. Exploration of internal rostral morphology has yielded valuable but previously unexplored characters that greatly complement the external characters of this structure. Together, these features provide new insight for settling current incongruence at the higher levels of classification.