Introduction

Abstract

The Staphylinidae is the largest family of beetles, consisting of more than 63,495 described species in 3762 genera worldwide (Newton, unpublished database, December 2017), and includes 1774 valid species recorded in Canada (Newton, unpublished database, December 2017). The Aleocharinae is by far the largest subfamily of rove beetles with 16,537 known species in 1310 genera and 62 tribes worldwide (Newton, unpublished database, December 2017). Aleocharinae is generally regarded as one of the most poorly known and most taxonomically challenging groups of Coleoptera worldwide. In Canada, there are 600 known species, and many species remain yet undiscovered including some that are undescribed. Aleocharinae constitutes at least 26% of all species within the family Staphylinidae. Rove beetles, including aleocharines, are useful as ecological indicators of changes in managed forests because of their highly specific microhabitat associations, response to disturbances, high local abundance and species, habitat, and trophic diversity, ease of collection, and availability of identification keys for many groups (Paquin and Dupérré 2002, Pohl et al. 2008, Venier et al. 2017, Klimaszewski et al. 2018). Usually, rove beetles represent a large proportion of the total abundance and species richness of organisms collected in pitfall traps, a sampling method frequently used to sample epigaeic arthropods. For example, Klimaszewski et al. (2005, 2007, 2008) reported that rove beetles were five times more abundant and three times more species rich than ground beetles, another taxon commonly used in the evaluation of impacts of forest management, in yellow-birch-balsam forests in Quebec. In another pitfall study of epigaeic fauna in the Cordilleran forests of western Alberta, the number of rove beetle species (including aleocharines) was two times greater and the number of specimens three times greater than that of carabid beetles (Langor, unpublished data). As well, rove beetles are present in high abundance and diversity in dead wood (Langor et al. 2008). Unfortunately, aleocharine assemblages are often neglected in biodiversity studies, including those that consider Staphylinidae, because of the difficulty in identifying many groups due to the dearth of comprehensive modern taxonomic treatments and identification keys and the labor-intensive need to dissect the genitalia of a large proportion of specimens to facilitate identification. However, we hope that this will change (at least in eastern Canada) with this publication that provides the necessary taxonomic keys for identification of 16 tribes, 97 genera and 407 species, complemented by high resolution imagery, including of genitalic structures that are highly diagnostic. This book is the first comprehensive treatment of the known species of Aleocharinae beetles distributed in eastern Canada (Ontario and eastwards). For each species we include a morphological diagnosis, distribution, and natural history. This work includes all commonly encountered aleocharines in eastern Canada and many uncommon and rarely collected species. We hope that these identification tools and information synthesis will inspire many new taxonomic and ecological studies of Aleocharinae throughout Canada. Additional work will help assess whether there are possible species at risk and will uncover the fascinating biology of this diverse and, often maddeningly, complicated group of beetles.