Plagiognathus atricornis Knight, 1926: 9

SCHUH, RANDALL T., 2001, Revision Of New World Plagiognathus Fieber, With Comments On The Palearctic Fauna And The Description Of A New Genus (Heteroptera: Miridae: Phylinae), Bulletin of the American Museum of Natural History 2001 (266), pp. 1-267 : 46

Plagiognathus atricornis Knight, 1926: 9 (n. sp.).

DIAGNOSIS: Recognized by the relatively small size and pale coloration (fig. 6), entirely black antennae (fig. 15) with the second segment 1.4 times as long as the width of the head, the large dark eyes, and the narrow vertex being about one­third the total width of the head. Compared with chrysanthemi by Knight (1926), but that species always greenish and with antennal segment 2 mostly pale rather than entirely black. Similar in size and coloration of the body to cibbetsi , polhemorum , and ribesi , but those species with antennae mostly pale, occurring only in western North America, and always feeding on Ribes , whereas atricornis appears to breed exclusively on Betula nigra in eastern North America.

REDESCRIPTION: Male: Relatively small, nearly parallel­sided; total length 3.03–3.73, length apex clypeus–cuneal fracture 2.39– 2.64, width across pronotum 1.01–1.06. COLORATION (fig. 6): General coloration, including venter and appendages, pale, greenish; membrane pale to weakly fumose; veins of membrane pale; antennae black except for pale apical annulus on segment 1 (fig. 15); apex of labium infuscate; femora with some dark spots; dorsal tibial spines with dark spots at bases; tibiae dark at femoral articulation. SURFACE AND VESTI­ TURE: Dorsum weakly granular, smooth, moderately shining. Vestiture of dorsum composed primarily of recumbent, pale, simple setae with dark setae on lateral margins of pronotum and basal costal margin of hemelytra. STRUCTURE: Body flattened, moderately broad; eyes large, bulging, vertex nar­ row, occupying about one­third width of head; frons nearly straight across in dorsal view, clypeus not visible from above; anteocular distance 0.3 times diameter of antennal segment 1; head projecting below level of eye by 0.6 times diameter of antennal segment 1; labium reaching to apex of middle coxae. GENITALIA (fig. 21): Vesica sigmoid, appearing strongly twisted, base falling well below level of secondary gonopore; anterior spine somewhat contorted, much shorter and somewhat broader than posterior, both spines twisted and strongly angled relative to body of vesica.

Female: Elongate ovoid, eyes much small­ er and vertex relatively broader than in male. Total length 3.53, length apex clypeus–cuneal fracture 2.42, width across pronotum 1.08.

HOST: Betula nigra (Betulaceae) .

DISTRIBUTION: Known from Pennsylvania south to Georgia and west to Iowa and Missouri.

DISCUSSION: Sexual dimorphism in the head is much more pronounced in this species than in most Plagiognathus spp. The eyes in the male are very large and protuberant, with the vertex being relatively narrow. By contrast, the eyes in the female are smaller, not protuberant, and the vertex is relatively broader. Although there is no evidence that atricornis is not a native species, the vesica shows its greatest similarity to that of chrysanthemi .

SPECIMENS EXAMINED: USA.— Georgia: Clarke Co.: Athens, June 26, 1955, R. Davis, 13 (PDA). Iowa: Lee Co.: Donnellson, September 3, 1927, H. G. Johnston, 23 (USNM). Monroe Co.: Albia, July 15, 1927, Harris and Johnston, 1♀ (USNM). Maryland: Prince Georges Co.: Bladensburg, July 23, 1890, P. R. Uhler, 1♀ (USNM). Missouri: Newton Co.: Neosho, June 22, 1943, R. C. Froeschner, 13 (USNM). Pennsylvania: Dauphin Co.: Harrisburg, near Rockville, July 16, 1979, T. J. Henry, Betula nigra (Betulaceae) , 33 (PDA). Snyder Co.: Pt. Trevorton, July 26, 1918, J. G. Sanders, 2♀ (USNM); holotype male (USNM). West Virginia: Braxton Co.: Burnsville exit, Rt 79 along Little Kanawha River, June 23, 1979, A. G. Wheeler, Jr., Betula nigra (Betulaceae) , 23 (PDA).