The New Zealand (Aotearoa) endemic ground beetle genus Mecodema Blanchard 1853 (Carabidae: Broscini: Nothobroscina) is hyper-diverse with a total of a 103 described species and subspecies, that are divided into seven species groups. Of the four Aotearoa nothobroscine genera, Mecodema is the most geographically widespread with species found throughout the North and South Islands and several offshore islands, including Three Kings (Manawatāwhi), Poor Knights (Tawhiti Rahi), Little Barrier (Hauturu), and Great Barrier (Aotea), Chatham’s (Wharekauri), Stewart (Rakiura) and the Snares (Tini Heke) Islands. In this study we synonymise M. crenaticolle Redtenbacher, 1868 under M. crenicolle Castelnau, 1867, with all North Island specimens now recognised as M. crenicolle. We reinstate M. venator Broun 1883, and all South Island specimens formally known as M. crenicolle are now recognised as M. venator. Contrary to Britton, we discuss the synonym M. variolosum Broun 1903 collected in ‘Rotorua’ as the only North Island specimen of M. venator. Species descriptions were formed using 126 morphological external and internal (both male and female genitalia) characters. This study identified three new South Island species: M. kahurangi sp. n. (ducale group), M. tititea sp. n. and M. altum sp. n. (laterale group). Redescriptions of three previously known South Island Mecodema species (M. ducale, M. allani, M. laterale) and one North Island only (M. crenicolle) are included.
Fong et al. (Thu,) studied this question.