Pachybrachis m-nigrum (F. E. Melsheimer, 1847)

Barney, Robert J., LeSage, Laurent & Savard, Karine, 2013, Pachybrachis (Coleoptera, Chrysomelidae, Cryptocephalinae) of Eastern Canada, ZooKeys 332, pp. 95-175 : 119

Pachybrachis m-nigrum (F. E. Melsheimer, 1847) Habitus 8 ; Map 8 ; Figure 6c

Cryptocephalus m-nigrum F. E. Melsheimer, 1847: 170.

Pachybrachys intricatus Suffrian, 1852: 180.

Recognition.

Pronotum usually with thick, black, M-shaped marking; elytra yellow with variable black markings, but these usually leaving basal, lateral and sutural margins yellow, in addition to a basal and median yellow spots on each elytron ( Habitus 8 ); male size medium: length 2.59 ± 0.11 mm, width 1.42 ± 0.07 mm.

Distribution.

A typical eastern species distributed in the eastern half of the United States ( Riley et al. 2003). Its presence in the south of the eastern Townships, in Québec, corresponds to the northernmost limit of this species ( Map 8 ).

Material examined.

NEW BRUNSWICK: York Co., 15 km W of Tracy, off Rt 645, 45.6837°N, 65.8809°W, 22.vii.2007, red pine forest, sweeping foliage of Comptonia peregrina , R. P. Webster [1?, RWIC].

QUÉBEC: Châteauguay Co., Ormstown, 12.VII.1977, sweeping, E. J. Kiteley [1♀, CNC]; same data, except 30.VII.1978 [1♂, CNC]; Huntingdon Co., Covey Hill, 30.VI.1927, G. S. Walley [1♀, CNC]; same data, except 1.VII.1927, W. J. Brown [1♀, CNC].

Host plants.

An old record by Schwarz (1890) concerned Toxicodendron radicans (L.) Kuntze) ( Anachardiaceae ), but this was probably based on misidentified specimens of Pachybrachis tridens . Clark et al. (2004) reviewed the literature. More recently, Webster swept it from Comptonia peregrina ( Myricaceae ) ( Webster et al. 2012). Recent surveying in Kentucky barrens/prairies by Barney et al. (2011) cited Pachybrachis m-nigrum collected from and found to feed on St. John’s-wort, Hypericum dolabriforme Vent. ( Clusiaceae ) ( Barney and Hall (2011)).

Comments.

Based upon external morphlogy, these specimens appear to be Pachybrachis m-nigrum . However, extensive dissections of material from across the eastern half of the US reveal an externally similar species, but with a distinctly different aedeagus, from the midwestern states (Barney, unpublished data).

Figures

Figure 6. Pronotum: a reddish, with close-up of marginal bead, Pachybrachis bivittatus b mottled, Pachybrachis spumarius c with black M-mark, Pachybrachis m-nigrum d almost black, Pachybrachis nigricornis carbonarius.

Habitus 8. Dorsal habitus of Pachybrachis m-nigrum. Scale bar, 1 mm.

Map 8. The known distribution of Pachybrachis m-nigrum in eastern Canada. CL - Champlain Lake; SLR - St. Lawrence River.