﻿A revision of the North American genus Proctorus (Coleoptera, Curculionidae, Ellescini) with descriptions of two new species

﻿Abstract The rarely collected North American endemic genus Proctorus (Coleoptera, Curculionidae, Ellescini) has hitherto contained two described species, P.armatus LeConte, 1876 and P.decipiens (LeConte, 1876). Here, Proctorus is revised and two new species, namely P.emarginatussp. nov. and P.truncatussp. nov., are described. Lectotypes for P.armatus and P.decipiens are designated from known syntypes. All four species in the genus are associated with Salicaceae, but, in addition to differences in external and genital morphology, there is also evidence of differing host plant usage between the species. A photographic key to the four species is provided to facilitate identification.

The purpose of this paper is to revise Proctorus and describe two new species, P. emarginatus sp. nov. and P. truncatus sp. nov., from North America.

Materials and methods
Specimens were borrowed from public and private insect collections as well as collected in the field. Institution names and associated acronyms used in this work are presented below: Specimens were dissected using standard protocols and genitalia were cleared in a water + KOH solution. The sexes were associated primarily by collection event (i.e., same day and locality). All examined specimens have Unique Specimen Identifier (USI) labels attached that read in the form: JHLRSA_PROC_###. All images were taken using a Leica Z16 APOA camera and LAS images stacking software (Leica Microsystems, Wetzlar, Germany).

Results
A taxonomic investigation of the genus Proctorus revealed the presence of an additional two species, namely P. emarginatus sp. nov. and P. truncatus sp. nov., with distinct external and genitalic (male) morphology. The fifth ventrite of males bear modifications (e.g., projections, carinas) that not only define the lineage more broadly, but also contain useful phylogenetic information and allow for unambiguous separation of males of the now four known species. Furthermore, there is some evidence of differing host plant usage between the species (see P. armatus species profile). Although females were dissected, no consistent differences in female genitalia were observed and thus females were largely identified by association with males taken during the same collection event (i.e., locality and date). Proctorus emarginatus is described here from three male specimens; the female remains unknown. This distinctive species is very rare, apparently restricted to northwestern North America, and has not been collected since 1988, when it was collected in the Northwest Territories. A photographic key to Proctorus along with profiles for each species are presented below. Diagnosis. Length 2.9-4.1 mm. Small, rounded, cuticle dark (black) or dark red and some species with dull orange, transverse stripe on elytra. Cuticle with coarse, white and/or yellow hair-like or more broad scales. Rostrum stout, roughly equal in length to pronotum, and often covered in scales up to antennal insertion. Eyes small and circular to oval, extending somewhat onto the rostrum medially. Antennae reddish with small, oval club. Pronotum as wide as long, coarsely punctate, scaled, and with or without prominent smooth, longitudinal midline. Scutellum not covered densely with bright white scales. Elytra oval in dorsal view, striae with large, deep punctures each bearing a scale. Punctures of elytral striae distinctly larger than those of pronotal disk. Interstrial regions of elytra with 2-4 irregular rows of scales. Fifth ventrite of male modified, with various projections and carinae. Fifth ventrite of female unmodified. Legs with femora toothed. Tarsal claws bearing basal tooth. Aedeagus rounded, subquadrate or emarginate at apex. Internal sac with hook-like sclerite. Diagnosis. Length 3.8-4.1 mm. Body (especially rostrum and femora) dark, although elytra often with orange stripe extending posteriorly from humerus. Protibiae of male dentate on inner edge. Elytra without clear, distinct x-pattern of white scales. Fifth ventrite of male with two prominent ventral projections apico-laterally which are connected by a transverse ridge; also with a single, smaller ventral projection positioned baso-medially. Apical tooth of metatibiae of male straight. Aedeagus in dorsal view slightly rounded to truncate, not emarginate or significantly expanded laterally.

Proctorus armatus
Notes on types. This species was described based on three specimens collected along the south side of Lake Superior. Two examined syntypes in the MCZC bear several types of labels. Both specimens bear a rectangular brown label reading "J.L. LeConte Coll.", a square red type label reading "Type 5224" and "Type 2 5224", and MCZC unique identifier labels (see specimens examined). One specimen also bears a rectangular brown label reading "Proctorus armatus Lec." and a rectangular white label reading "Jan.-Jul. 2005 MCZ Image Database". The location of the third (male) syntype specimen is unknown; however, the identity (i.e., P. armatus) of that specimen is clear, based on LeConte's original description. Here, we designate one of the known P. armatus syntypes (MCZ-ENT00005224) as a lectotype to fix the identity of this species.
Taxonomic comments. See same section for Proctorus truncatus.
Remarks. This species is likely most closely related to P. truncatus as males of both species bear a basomedial projection on the fifth sternite (lacking in other species; males only), have a straight metatibial spur (lacking in P. decipiens; only males), and are both large and dark in general form. Furthermore, examined specimens of P. truncatus and P. armatus were only collected from Populus when such data was recorded, whereas examined specimens of P. decipiens and P. emarginatus have only been collected from Salix species. Although more field data should be amassed to support this difference in host plant preference, an emerging pattern of differing host plant preference is apparent and supports the hypothesis that P. truncatus and P. armatus are closely related.
Etymology. The specific name refers to the truncate ventral projections on the fifth ventrite of males (compare with P. armatus which has long ventral projections).
Ecology. This species has been collected from Populus grandidentata Michx. and P. tremuloides Michx. The single record of a specimen (JHLRSA_PROC_267) from Pinus contorta Douglas ex Loudon is likely incidental.
Taxonomic comments. This species was long confused with the less common P. armatus from which it differs in the armature of the fifth ventrite (males), protibia dentation (males), genitalia (males), rostrum length (females) and overall body shape (both sexes). LeConte (1878: 620) wrote of P. armatus (two years after describing that species): "Several specimens of this curious insect were found at Marquette, and among them are ♂♂ in which the two processes of the apical edge of the fifth ventral segment are very short, and scarcely apparent, though the anterior tubercle or spine and the large excavation are as well developed as in the other specimens." Clearly, LeConte is referring to our new species P. truncatus; however, he apparently assumed that the differences in ventrite armature were cases of intraspecific variation in P. armatus as no additional species were described.   Diagnosis. Length 2.9-3.1 mm. Body (especially rostrum and femora) dark, although elytra often has orange stripe extending posteriorly from humerus. Protibiae of male not prominently dentate on inner edge. Elytra without clear, distinct x-pattern of white scales. Fifth ventrite of male with a single transverse ridge which peaks medially; without any baso-medial ventral projection. Apical tooth of metatibiae of male straight. Aedeagus with apex distinctly emarginate and with four prominent lobes (two on each side).
Etymology. The specific name refers to the apically emarginate body of the penis. Ecology. One specimen was collected from Salix. However, nothing else is known of the natural history of this species.
Remarks. This species is known only from northwestern North America (only Canada at present), and based on institutional collection records also represents one of the rarer weevils in Canada. The female of P. emarginatus is unknown.

Discussion
Proctorus represents a morphologically distinct monophyletic lineage that is endemic to North America. The specific armature on the fifth ventrite of males is unique to the genus within North America; however, we note that the males of the Old World species Dorytomus dorsalis (Linnaeus, 1758) also possesses similar structures. Although Proctorus is currently placed in the subtribe Ellescina with Ellescus (Alonso-Zarazaga and Lyal 1999; Anderson 2002;Bousquet et al. 2013;Caldara et al. 2014;Alonso-Zarazaga et al. 2017), the shared ventral armature in Proctorus and Dorytomus (subtribe Dorytomina) hints at a closer phylogenetic relationship between those genera than previously thought. Preliminary molecular work suggests that Proctorus represents a lineage sister to or nested within Dorytomus. However, improved taxon and gene sampling is required to improve branch support and determine which of those phylogenetic hypotheses is correct (unpublished data, Lewis and Anderson). Here, we take a conservative approach and continue to recognize the validity of Proctorus as members of that genus are morphologically separable from all Dorytomus species (including D. dorsalis) by tarsal claw morphology.
Although the species of Proctorus are easily distinguished by external and internal morphology, two species described here were long overlooked. This is likely due to the fact that specimens of the genus are rare in institutional collections. Indeed, P. emarginatus sp. nov. is only known from three specimens. Future studies of the genus should focus on surveying for the female of P. emarginatus and further investigating differing host plant usage amongst the species.