Description of the larva of Mitosynum vockerothi Campbell, 1982, with remarks on the adult male genital morphology (Coleoptera, Staphylinidae, Oxytelinae)

Abstract The previously unknown larva of Mitosynum vockerothi Campbell, 1982, is described and illustrated. Adult male terminalia and genitalia are illustrated with line drawings. Adults of this species exhibit little difference in size or external morphology between males and females.


Introduction
The genus Mitosynum Campbell, 1982, includes a single species that is endemic to New Brunswick, Canada (Herman 2001, Webster et al. 2012. The description by Campbell (1982) was based on two female specimens, with the habitus illustrated by a line drawing, but genital morphology was not discussed, no measurements of the adults were provided, and the larva was unknown. The first color habitus photo appeared in Makranczy (2006). A subsequent contribution included new records for the genus and species, plus a color image of the adult and the first black and white photographic images of the aedeagus (Webster et al. 2012). The genus is now included in the tribe Syntomiini Böving & Craighead, 1931(Khachikov 2012. The former Deleasterini Reitter, 1909 included six genera (Platydeleaster Schülke, 2003, Deleaster Erichson, 1839, Syntomium Curtis, 1828, Mitosynum Campbell, 1982, Euphanias Fairmaire & Laboulbène, 1856and Oxypius Newton, 1982 and was treated as the Euphaniini Reitter, 1909 by Bouchard et al. (2011), the latter name originally proposed at a higher rank and therefore being of priority. This assemblage of genera is heterogenous, as it includes three monobasic genera and their morphological diversities are poorly mapped, and none were ever revised. Khachikov (2012) speculatively modified the tribal classification, based on a few dissections made on common Palaearctic representatives. This involved breaking up the aforementioned assemblage into three different tribes. This system is at best considered tentative and more analyses are required based on additional characters to test the new hypothesis, with the inclusion of the exotic taxa and assessing the variabilities of the wider distributed, non-monobasic genera. Within the former group of six genera, the larvae of Deleaster Erichson, 1839 and Syntomium Curtis, 1828 are known, but the only complete description is provided for Oxypius Newton, 1982, an Austral endemic relict (Newton 1982). In this contribution, we provide a description of the previously unknown larva of Mitosynum and male genitalia that will be useful for a future more detailed analysis of the above tribal classification. In addition, we provide measurements of various structures of the adult not included in the original description.

Material and methods
One larval specimen of M. vocherothi, not mentioned by Webster et al. (2012) was collected along with the nine adults reported in that paper. No other Oxytelinae were found at the site and habitat where the larva was found, a large hummock of Sphagnum and Polytrichum commune Hedw. near a pond margin (Webster et al. 2012). The specimen bears the characteristic metallic luster of the adults ( Fig. 6; see Figure 1 in Webster et al. 2012 for comparison with the adult), leaving little doubt about the correct assignment of the larval specimen. It is unlikely a mature larva, as the size is significantly smaller than that of the adults. However, due to the rarity of this species, we describe the larva here. Based on two male, two female, and four unsexed adult specimens, we also describe and discuss some genitalia features of the adult male and provide measurements of some key structures not included in the original description by Campbell (1982).
The larval specimen was originally dry mounted but subsequently cleared and examined in glycerol following a protocol established in Makranczy (2016). Adult genitalia drawings were made after embedding them into Euparal mounting medium on small plastic slides that were pinned with the specimens according to Makranczy (2006). As the aedeagus is very similar to that in Deleaster Erichson, 1839, the illustration technique used by Cuccodoro and Makranczy (2013) was applied. Drawing was done with a Jenalab (Carl Zeiss, Jena) compound microscope and drawing tube (camera lucida). For color habitus photography, a Nikon D4 camera with Mitutoyo PlanApo 5x ELDW lens was used, and layers montaged with ZereneStacker.
The examined specimens are deposited in the Canadian National Collection of Insects, Arachnids, and Nematodes, Ottawa, Canada (CNC), the Hungarian Natural History Museum, Budapest, Hungary (HNHM), and the private collection of Reginald Webster, Charters Settlement, New Brunswick, Canada (RWC). Male terminalia and genitalia. Sternite VIII apex in males almost truncate but with rounded corners. Tergite IX with strongly developed but short ventral strut. Tergite X strongly attached (Fig. 1). Aedeagus (Figs 2-5) very strongly sclerotized, dark. Apical opening processes of median lobe strong and elongate. Parameres elongate and rounded at apices. Apical part of paramere (Fig. 3) with a couple of very short peg-like setae. Internal sac with a sclerotized, symmetrical sclerite (Figs 4, 5).
The apical opening processes of the aedeagus and parameres very strongly resemble those in Deleaster Erichson, 1939. The presence of a few very short peg-like setae (Fig. 3) on the apical part of paramere was not previously known in Oxytelinae. The distinct, symmetrical inner sclerite is the first observation of this character within the six genera of Deleasterini sensu Makranczy (2006).