INTRODUCTION. The South American weevil species complex Listroderes costirostris Schoenherr (“vegetable weevils”) is comprised of three species: L.costirostris, Listroderes difficilis, and Listroderes obliquus. Due to the morphological similarities between the females and the scarce males (parthenogenetic species), there is no consensus about whether they correspond to a single species or three valid ones. These species are agricultural pests of several crops in their countries of origin and where they were introduced.

METHODS. For the morphometric analysis, three structures or regions were considered: rostrum in frontal view (HF), rostrum in lateral view (HL), and pronotum in lateral view (PL), for a total of 135 females (45/ species). Landmarks and curve semilandmarks were established with TPSDig. Procrustes analysis, Principal Component Analysis (PCA), Canonical Variates Analysis (CVA), and discriminant analysis (DA) were performed in MorphoJ and Geomorph 4.2 in R. The structures were analyzed independently.

RESULTS. In the PCA, all species were differentiated only using the PL structure. In the CVA the species have significant differences (P< 0.0001) in all structures analyzed. The DA also showed significant differences between species in the three structures studied.

CONCLUSIONS. Concluding, the three species of the L. costirostris complex could be differentiated based on morphometrics. The structures of the head and pronotum are useful for this differentiation, mainly the lateral view of the pronotum. As a future step, we need to correlate the morphometric variation observed with the genetic divergence within this group.