DESCRIPTION OF FIRST-INSTAR LARVA OF METRIUS CONTRACTUS ESCHSCHOLTZ (COLEOPTERA: CARABIDAE) WITH REMARKS ABOUT PHYLOGENETIC RELATIONSHIPS AND RANKING OF THE GENUS METRIUS ESCHSCHOLTZ

Abstract

AbstractThe 1st-instar larva of Metrius contractus Eschscholtz is described and illustrated. The larva differs from those of other Carabidae (except some species of ozaenines) by having the epipleurites of the 9th segment and the tergum of the 8th segment transformed into a plate and by having the urogomphi antler-like and located in a vertical plane. These character states support the hypothesis, based on published analysis of the adult structures, that the monogeneric tribe Metriini is closely related to the tribes Ozaenini and Paussini. The ranking of Metrius, Ozaenini, and Paussini is re-evaluated and it is proposed that these three groups be combined in one tribe, the Paussini (sensu novo). The tribe Paussini, thus constituted, is placed with the tribes Brachinini and Crepidogastrini in the subfamily Paussinae. The relationships of the subfamily are unclear, but it probably represents a primitive element of the Carabidae. Based on the available data on bionomics and larval morphology of paussines, it is suggested that larvae of Metrius live in rotten logs and depend for their survival on some kind of animal which they attract through a secretion released at the extremity of the abdomen. The kind of animal and the type of interaction between the animal and the Metrius larvae remain unknown.