Morphological and molecular identification of Carpophilus dimidiatus (Coleoptera: Nitidulidae) associated with stored walnut in Northwestern Argentina

The beetle genus Carpophilus (Coleoptera: Nitidulidae: Carpophilinae) includes important stored-product pest species, many of which are widespread worldwide and often difficult to identify using external morphological features. The present research work provides the identification of Carpophilus dimidiatus (Fabricius), infesting walnut in production areas in Catamarca Province, Northwestern Argentina, these being new host and distribution records for the province. It was based on both morphological and molecular information. In order to ensure accuracy and facilitate further studies requiring recognition of taxonomically challenging species of Carpophilus, a revised morphological diagnosis of C. dimidiatus is provided and illustrated with photos of habitus of adult male and female and of relevant external and genital characters, including comparative notes to allow distinction of this species from other similar nitidulid beetles. For molecular identification of C. dimidiatus, sequencing of the 5′ and the 3′regions of the mitochondrial cytochrome c oxidase I (COI) gene was performed. Fragments of 658 bp and ∼800 bp, respectively, are made available as additional diagnostic tools. Phylogenetic analyses were also done on the barcode fragment of COI of several Carpophilus species and outgroup taxa, available in genetic databases, with results confirming the species identity.