Redescription of Stenolophus thoracicus Casey (Coleoptera, Carabidae, Harpalini), a valid species

Abstract Stenolophus thoracicus Casey is revalidated. The species is redescribed based on a study of the syntypes and of several conspecific specimens from eastern North America. The species differs from the other eastern species of the subgenus Agonoleptus in having the metasternum shorter and the wings reduced to tiny stubs. The dorsal habitus and median lobe of the aedeagus, along with the structures of the internal sac, are illustrated.


Introduction
, in his comprehensive monograph of the carabids of Canada and Alaska, synonymized Stenolophus thoracicus Casey with S. conjunctus (Say) pointing out, however, that the microsculpture on the pronotum of the female "type" was considerably stronger than normal. A study of Casey's syntypes revealed that the specimens are in fact specifi cally distinct from those of S. conjunctus. Th e purpose of this paper is to redescribe S. thoracicus and to discuss the structural diff erences between S. thoracicus and the other eastern species of the subgenus Agonoleptus Casey.
Th e holdings of the following collections were studied: Buff alo Museum of Science, New York (BMSC), California Academy of Sciences (CAS), National Collection of Insects, Arachnids  Type material. Lectotype (♂), designated by Lindroth (1975: 143), in USNM labelled: "Mo / ♂ / Casey bequest 1925 / thoracicus Paratype USNM 48052 / Lectotype thoracicus Csy by C.H. Lindroth." Casey's collection includes six other specimens under the name S. thoracicus (one ♀, fi ve ♂), each labelled later as "paratype." Th e unit tray bears a label "type missing Lindroth 73." It seems that the Casey's collection included another female specimen, labelled as "type," that Lindroth studied before 1968. Description 1 . Coloration. Clypeus and labrum reddish; frons reddish-brown to reddish-black; antennomeres 1 and 2 yellow, antennomeres 3-11 slightly darker, brownish-yellow; pronotum entirely yellow to reddish-yellow; elytra reddish-brown to reddish-black, with base, intervals 1 and lateral margins paler, more or less yellowish to reddish; elytral epipleura yellow; legs entirely yellow. Microsculpture. Frons with isodiametric meshes, meshes indistinct or almost so in the male, faint but distinct in the female; pronotum with linear microlines, microlines indistinct or almost so in the male, distinct in the female; elytra with markedly transverse meshes, meshes well impressed in both sexes. Head. Clypeo-ocular line evident, complete (i.e., reaching medial edge of eye). Pronotum. Proportionally wide, LP/WP = 0.73-0.79 (mean = 0.76; n= 10); maximum width clearly anterior to middle; anterior angle markedly protruding; basal impression shallow, almost indistinct in some specimens; basal bead reaching just beyond level of basal impression. Elytra. Striae impressed, shallow but deeper toward apex, impunctate; intervals fl at. Th orax (ventral side). Metasternum, short, length behind mesocoxa about 0.7 that of metacoxa along same line. Male genitalia. Median lobe with apex hooked; internal sac with two large U-shaped sclerotized structures and a small "scaly body" near middle.

1
For character states of the subgenus Agonoleptus, see Lindroth (1968: 921), as "the conjunctus group." Geographical distribution. Th is species ranges from east-central Vermont to southeastern North Dakota, southwardly to northeastern Kansas, Tennessee, and northeastern Virginia (Fig. 3). We have seen specimens from the following localities.   Wing condition. Nine specimens were dissected and their wings were reduced to tiny stubs. Considering the size of the metasternum, the species is very likely constantly brachypterous.
Note. Stenolophus thoracicus belongs to the subgenus Agonoleptus Casey which includes six other species-group taxa: S. conjunctus (Say), S. rotundicollis (Haldeman), S. rotundatus LeConte, S. parviceps (Casey), S. unicolor Dejean, and S. unicolor dolosus Casey. Th e last three-named taxa are found in southwestern United States and are not further dealt with. Th e other taxa occur sympatrically with S. thoracicus east of the Rocky Mountains, although one of them, S. conjunctus, also extends to the West Coast.
Adults of S. thoracicus diff er most notably from those of the three other eastern species of the subgenus in having the metasternum shorter and the wings highly reduced. For comparative purpose, the ratio of the metasternal length behind the mesocoxa and the metacoxal length measured along the same line varies between 1.0 and 1.2 in S. conjunctus, S. rotundicollis, and S. rotundatus. In addition, the pronotum is more narrowed posteriorly on average.
Adults of S. conjunctus diff er from those of S. thoracicus also in having the microsculpture on pronotum indistinct in both sexes and the elytral microsculpture less impressed. Th e apex of the median lobe of the aedeagus is proportionally longer, not hooked, and the internal sac has two slightly curved sclerotized structures (see Lindroth 1968: Fig. 446a).
Adults of S. rotundicollis diff er from those of S. thoracicus also in having the pronotum darker, brownish-red to reddish-brown (except narrowly around the edges) and the microsculpture on pronotum and elytra more deeply impressed. Th e apex of the median lobe is hooked but the internal sac contains two small U-shaped and one slender, straight sclerotized structures (see Lindroth 1968: Fig. 446c).
Adults of S. rotundatus diff er from those of S. thoracicus also in having the pronotum darker, reddish-brown to piceous (except for anterior and posterior margins), and more convex, the clypeo-ocular line clearly more deeply impressed, the anterior angles of the pronotum less protruding, the medial elytral striae deeper, and the pronotum and elytra without microsculpture. Th e apex of the median lobe is hooked, more bluntly so than in S. thoracicus and S. rotundicollis, and the internal sac has one large U-shaped and one straight sclerotized structures (see Lindroth 1968: Fig. 446b).