Pachybrachis atomarius

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: 11-12

publication ID 10.1649/0010-065X-72.1.9

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Pachybrachis atomarius


atomarius   species-group

Group Diagnosis. Small species, males measuring 1.64–2.42 mm in length. Dorsum glabrous with coloration ranging from yellow mottled with

brown or black markings to black. Eyes of males closely to moderately widely separated (IOD = 0.09-0.37 mm); front without ocular lines. Protarsal claws of males not enlarged. Median lobe of male genitalia with basal plates simple (except for Pachybrachis stygicus Fall   ); DEO generally parallel-sided, often with an arrowhead-shaped distal end arising from a narrowing at the ALM, deflexed at a 30–90° angle, some with denticles at ALA); beard setae short in patches; pencilli absent.

Remarks. The atomarius   species-group, as proposed here, is an artificial grouping of small, yellow-brown-black-maculated species, primarily found in the eastern USA. A distinguishing characteristic of many species within this group is that the distal end of the median lobe is arrowhead-shaped, deflexed 30–90°, often with denticles, which may represent a natural speciesgroup. I propose the atomarius   species-group to include 24 Nearctic species: Pachybrachis archboldi Barney   ; Pachybrachis atomarius (F. E. Melsheimer)   ; Pachybrachis calcaratus Fall   ; Pachybrachis caroleae Barney   , new species; Pachybrachis cephalicus Fall   ; Pachybrachis charlotteae Barney   , new species; Pachybrachis confederatus Fall   ; Pachybrachis conformis Suffrian   ; Pachybrachis dixianus Fall   ; Pachybrachis erinae Barney   , new species; Pachybrachis gibbyi Barney   , new species; Pachybrachis gibsoni Barney   , new species; Pachybrachis jacobi Barney   , new species; Pachybrachis lodingi Bowditch   ; Pachybrachis luctuosus Suffrian   ; Pachybrachis matthewi Barney   , new species; Pachybrachis mcmeansi Barney   , new species; Pachybrachis osceola Fall   ; Pachybrachis parvus Fall   ; Pachybrachis quadrioculatus Fall   ; Pachybrachis relictus Fall   ; Pachybrachys stygicus Fall   ; Pachybrachis varians Bowditch   ; and Pachybrachis walteri Barney   , new species. Pachybrachis archboldi   , P. conformis   , and P. osceola   (only four known specimens from Central Florida and not included in key) were addressed in Barney (2016a) and will not be redescribed here.

Biology. Almost nothing is known of the biology of the members of the atomarius   species-group. Pinus spp.   ( Pinaceae   ), Quercus spp.   ( Fagaceae   ), Hypericum spp.   ( Hypericaceae   ), and many legumes ( Fabaceae   ) are among suspected host plants. The website The Plant List ( was used to verify species. Larvae and larval habitats are unknown.