Pachybrachis calcaratus 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 : 20-21

3. Pachybrachis calcaratus Fall, 1915 ( Fig. 3 , Map 1A)

Pachybrachys calcaratus Fall 1915: 389 . Knaus 1916 –1917: 262 (regional species list); Hicks 1947: 117 (regional species list); Wilcox 1954: 390 (taxonomy).

Pachybrachis calcaratus: Riley et al. 2003: 155 (catalogue); Clark et al. 2004: 158 (plant associations); Barney et al. 2013: 116 (taxonomy).

Type Material. Fall’ s male type, herein designated as lectotype and labeled “N.Ill. [printed, white paper] // Hinsdale / 6/21/93 [hand-inked, white paper] // 6 // TYPE [printed, white paper] / calcaratus [hand-inked, white paper] // M.C.Z. / TYPE 29920 [hand-inked, red paper] // H. C. FALL / COLLECTION [printed, white paper] // LECTOTYPE 29920 / Pachybrachys / calcaratus Fall 1915 / R. J. Barney 2017 [printed, red paper]”, was examined and photographed ( Fig. 3 ).

Redescription. Male. Yellow with fuscous maculae to almost black; L = 2.03–2.29 mm (mean = 2.14 mm, n = 10); W = 1.00– 1.19 mm (mean = 1.08 mm, n = 10); L/W = 1.89–2.05 (mean = 1.97, n = 10). Head: Not wider than thoracic apex, HW = 0.68–0.77 mm (mean = 0.73 mm, n = 10); eyes narrowly separated, IOD = 0.16–0.21 mm (mean = 0.18 mm, n = 10); IOD/HW = 0.22–0.28 (mean = 0.25, n = 10); face yellow with brown to black, W-shaped macula connecting the vertex and bases of antennae, and up to base of upper lobe of eyes, punctation dense, antennae yellow-brown, not reaching elytral declivity. Pronotum: Yellow, M-shaped macula dark brown to black, broadly diffuse; incomplete punctation to lateral margins; PL = 0.61–0.73 mm (mean = 0.68 mm, n = 10); PW = 0.92–1.06 mm (mean = 0.98 mm, n = 10); PL/PW = 0.67–0.73 (mean = 0.69, n = 10). Elytra: Yellow, coarsely punctate with fuscous maculae often broadly diffuse to become general color with small, scattered yellow areas; outer striae distinctly impressed. Pygidium: Black, with 2 oval, yellow maculae. Venter: Black, upper sides of last ventrite yellow. Legs: Dark brown to black, with standard yellow spots; protibia with subapical rectangular tooth on inner margin and long stout curved terminal spur ( Fig. 3 ). Genitalia: Median lobe in en-face view with OS appearing almost round, flattened with large basal plates, POL slightly extended and gently rounded with setae; in lateral view, a flat, broad keel is seen ( Fig. 3 ). Thirty-three males from 12 states were dissected.

Female. As in male, except terminal tibial spur much reduced, L = 2.10–2.50 mm (mean = 2.37 mm, n = 10); W = 1.17–1.33 mm (mean = 1.26 mm, n = 10); L/W = 1.79–1.90 (mean = 1.88, n = 10); HW = 0.76–0.90 mm (mean = 0.83 mm, n = 10); IOD = 0.24–0.30 mm (mean = 0.28 mm, n = 10); IOD/HW = 0.31–0.36 (mean = 0.33, n = 10).

Remarks. Pachybrachis calcaratus is one of only three Pachybrachis species known to have the sexual tibial spur character of the male, and the only species in the eastern USA. Pachybrachis texanus Bowditch and Pachybrachis uncinatus Fall share the tibial spur character, but are only known to occur in Texas and Arizona, respectively.

Distribution. This species is found from Minnesota and Michigan south to Louisiana and Florida. New state records are confirmed for seven states: Florida, Minnesota, Mississippi, Ohio, Oklahoma, South Carolina, and Texas (Map 1A). Of the specimens I examined, 81% were from three states adjacent to the Mississippi River: Illinois, Louisiana and Mississippi.

Biological Notes. Lythrum salicaria L. ( Lythraceae ) was listed on a specimen label from Ohio. In 1947, Milt Sanderson, of the Illinois History Survey , collected 77 specimens near the lectotype locale in northern Illinois and identified the host plant as “Host #103”. Unfortunately, his notebooks could not be found, and the plant remains unknown (Dmitry Dmitriev, personal communication) .

Specimens Examined. See Appendix 3.

Figures

Fig. 3. Pachybrachis calcaratus, 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.