Pachybrachis relictus Fall, 1915

Barney, Robert J., 2018, Definition and Revision of the Atomarius Species-Group of North American Pachybrachis Chevrolat (Coleoptera: Chrysomelidae: Cryptocephalinae), Including Descriptions of Nine New Species, The Coleopterists Bulletin 72 (1), pp. 9-74 : 29

10. Pachybrachis relictus Fall, 1915 ( Fig. 10 , Map 2A)

Pachybrachys relictus Fall 1915: 424 . Wilcox 1954: 391 (taxonomy).

Pachybrachis relictus: Downie and Arnett 1996: 1319 (catalogue); Barney 1984: 141 (regional species list); Riley et al. 2003: 163 (catalogue); Clark et al. 2004: 161 (plant associations).

Type Material. Fall’ s male type, herein designated as lectotype and labeled “Frmghm. / Mass. / Frost [printed, white paper] // VIII-14-07 [handinked] // 6 // TYPE / relictus [hand-inked, white paper] // Type 24976 [hand-inked, red paper] // H. C. FALL / COLLECTION // LECTOTYPE 24976 / Pachybrachys / relictus Fall 1915 / R. J. Barney 2017 [printed, red paper]”, was examined, photographed, and dissected ( Fig. 10 ) .

Redescription. Male. Yellow, with dark brown to fuscous punctures, standard maculae diffuse; L = 1.97–2.28 mm (mean = 2.13 mm, n = 10); W = 1.02–1.18 mm (mean = 1.10 mm, n = 10); L/W = 1.84–2.09 (mean = 1.94, n = 10). Head: Slightly wider than thoracic apex, HW = 0.69–0.77 mm (mean = 0.72 mm, n = 10); eyes moderately separated, IOD = 0.18–0.21 mm (mean = 0.19 mm, n = 10), IOD/HW = 0.25–0.29 (mean = 0.27, n = 10); face yellow with dark brown to black, W-shaped macula connecting the vertex and bases of antennae and up to base of upper lobes of eyes, punctation dense, antennae yellowbrown, almost reaching elytral declivity. Pronotum: Yellow, dark brown to black M broadly diffuse, leaving small, scattered, yellow spots, incomplete punctation to side margins, PL = 0.62–0.71 mm (mean = 0.66 mm, n = 10); PW = 0.90–1.04 mm (mean = 0.93 mm, n = 10); PL/PW = 0.69–0.73 (mean = 0.71, n = 10). Elytra: Confused punctures in basosutural region, striae impressed, especially posteriorly and laterally, irregular in middle, marginal interspace mostly impunctate. Pygidium: Dark brown to black with 2 oval, yellow maculae. Venter: Dark brown to black, upper sides of last ventrite yellow. Legs: Dark brown to black with standard yellow spots. Genitalia: Median lobe in en-face view with wide, parallel-sided shaft, gently rounding to terminus, with sclerotized, lateral basal plates and reduced PRL. POL, best seen in the lateral view, with ALA deflexed near 60°. Base wide, with mid-keel or ridge eventually narrowing at ALA. Long setae present along edges of deflexation, but no denticles present at ALM ( Fig. 10 ). Thirty-nine males from 14 states and provinces were dissected.

Female. As in male, except L = 2.07–2.46 mm (mean = 2.26 mm, n = 9); W = 1.15–1.31 mm (mean = 1.23 mm, n = 9); L/W = 1.77– 1.91 (mean = 1.84, n = 9); HW = 0.71–0.84 mm (mean = 0.79 mm, n = 9); IOD = 0.23–0.32 mm (mean = 0.28 mm, n = 9).

Remarks. Fall (1915) believed that P. relictus was a widely dispersed species in the northeastern USA, being found from New York to Tennessee. Dissection of many males in the MCZ-FALL and MCZ collections, each bearing a Fall identification label, revealed a mixture of four species: true P. relictus from Massachusetts (as compared to the lectotype); P. gibsoni from Massachusetts (labels often read “ relictus var (?)”, some with same label as lectotype); P. mcmeansi from Massachusetts and Tennessee; and P. luctuosus from New Jersey. This illustrates the difficulty in separating Pachybrachis specimens from the same collecting event to species, pre-dissection, even for an expert like Fall.

Distribution. Pachybrachis relictus is found in the northeast from Québec and Maine to Indiana and South Carolina. New state records are confirmed for four states: Michigan, New Hampshire, North Carolina, and South Carolina (Map 2A).

Biological Notes. A label cited a specimen collected from Quercus sp. in Ontario.

Specimens Examined. See Appendix 10.

Figures

Fig. 10. Pachybrachis relictus, lectotype. A) Dorsal habitus, B) Lateral habitus, C) Face, D) Pygidium, E) Median lobe of aedeagus, lateral view, F) Median lobe of aedeagus, en-face view.