Proceratium crassicorne

Wesson & Wesson (1940) between 1934 and 1939 within 45 miles from Jackson (Ohio) collected crassicorne four times in dry soil, in open woods under stones or moss. These authors collected a colony of crassicorne comprising 30 workers, a dealate female, about 8 males, 2 cocoons, 5 naked pupae and a few small larvae from the soft portion of a rotten log. (Baroni Urbani and de Andrade 2003)

Identification
A Proceratium species belonging to the silaceum clade, similar to silaceum but differing from it, in the worker, gyne and male, by the sculpture less impressed, in the worker and gyne by the frontal carinae narrower and by the hairs of type (1) denser on the gaster, in the gyne only by the eyes smaller (≤ 0.17 mm instead of ≥ 0.19 min).

Workers and queens have a high, more or less rectangular petiole (in lateral view), distinguishing them from Proceratium pergandei, Proceratium compitale, Proceratium californicum, Proceratium creek, Proceratium chickasaw and Proceratium mexicanum. The mesosoma is evenly convex in lateral view, unlike that of Proceratium croceum. This species is similar to Proceratium silaceum, differing in the density of hairs on the gaster, especially the second gastral tergite. As each hair emerges from a small puncture, the disc of the second gastral tergite appears closely punctate, with most of the punctures only one or two puncture-widths apart when seen under a diffuse light, such as that of a flourescent bulb. The tergite of P. silaceum is sparsely punctate, with most punctures separated by several puncture-widths.

Distribution
Known from New York south into northwest Florida, west into Missouri and Arkansas.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.



Biology
The habitat of this species is hardwood forest, including ravines of the Florida Panhandle. The diet is certain to be the eggs of arthropods, especially spiders, as reported for the similar species Proceratium silaceum. Actually, it is not clear which of the dietary records for P. silaceum (Brown 1958a, 1958b) apply to that species and which apply to P. crassicorne, as Brown only recognized one species, which he called P. silaceum.

Nomenclature

 *  crassicorne. Proceratium crassicorne Emery, 1895c: 265, pl. 8, fig. 9 (w.) U.S.A. Smith, M.R. 1928b: 244 (q.); Wheeler, G.C. & Wheeler, J. 1952a: 137 (l.); Baroni Urbani & De Andrade, 2003b: 426 (m.). Junior synonym of silaceum: Creighton, 1950a: 40; Brown, 1958g: 248. Revived from synonymy: Baroni Urbani & De Andrade, 2003b: 422.

Taxonomic Notes
When Creighton (1950) synonymized Proceratium silaceum and Proceratium crassicorne, he included a detailed commentary on the illusory nature of the supposed differences in the shape of the petiole in the two species. In spite of this, there really does seem to be a small but consistent difference in the petiolar profile, with P. crassicorne less narrowed above than P. silaceum. In addition, the petiole of P. crassicorne is less shining at the base of the petiolar scale, the basal carina of the petiolar scale is less developed, the petiole is more pubescent, especially the anterior face near the base. The frontal carinae of P. crassicorne project more above the surface of the head and are less expanded than in P. silaceum.

Baroni Urbani and de Andrade (2003) - We considered Proceratium crassicorne as a valid species and not a synonym of Proceratium silaceum as proposed by Creighton (1950) since the characters listed in the diagnosis to separate the two species are consistent within all the material that we studied. The study of the male genitals of both species reveals small but significant differences between crassicorne and silaceum, i.e. the shape of the stipes and of the subgenital plate. Since, as already noted by Emery (1895), the two coexist in narrow sympatry, there seems to be no other alternative to consider them as valid, separate species. In the present paper we report additional records of both species from the same locality (e. g. in Tennessee).

Worker
Baroni Urbani and de Andrade (2003) - Head slightly longer than broad with the sides gently diverging posteriorly. Vertex in full face view gently convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae closer to each other than in silaceum. Lateral expansions of the frontal carinae less broad than in silaceum, slightly raised, diverging on the two anterior fourths, gently converging on the third fourth and subparallel on the last fourth. Frontal area gently concave, posteriorly with a median, longitudinal carina prolonging backwards. Head anterolaterally with a variably marked longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a deep sulcus. Eyes visible as a dark dot below the integument, small and placed on the middle of the head sides. First funicular joint slightly longer than broad. Funicular joints 2-10 broader than long. Last funicular joint slightly longer than the sum of joints 7-10. Scapes short of the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 7-8 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma in side view weakly convex on the two anterior thirds, gently sloping on the posterior third. Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Area between the basal and declivous faces of the propodeurn gently concave dorsally and variably carinate. Each side between the basal and declivous faces of the propodeum with a tooth. Declivous face of the propodeum gently sloping posteriorly. Sides of the declivous face of the propodeum carinate. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular. Anterior border of the petiole straight and anterolaterally narrowly marginate. Ventral process of the petiole lamelliform and pointed posteriorly. Postpetiole in dorsal view with the sides diverging on the anterior half and gently convex on the posterior half. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently convex posteriorly in side view. Constriction between postpetiole and gaster impressed. Gastral tergite I about 1/3 longer than the postpetiole and convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs moderately elongate. All tibiae with a pectinate spur. Spurs of fore legs without basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 1/4 shorter than the hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head, mesosoma, petiole and postpetiole minutely punctate, reticulorugose, the reticulation and the rugosities larger on the sides of the head, the rugosities absent on the petiole and postpetiole. First gastral tergite smooth and with minute piligerous punctures. Legs punctate.

Pilosity as in Proceratium silaceum but with hairs of type (1) better covering the integument and hairs of type (2) slightly sparser and shorter.

Colour. Dark yellow to light brown with slightly lighter antennae and legs.

Measurements in mm and Indices: TL 2.74-3.03; HL 0.62-0.67; HW 0.58-0.64; EL 0.02-0.04; SL 0.41-0.44; WL 0.74-0.83; PeL 0.19-0.20; PeW 0.26-0.29; HFeL 0.44-0.49; HTiL 0.37-0.41; HBaL 0.28-0.31; LS4 0.30-0.35; LT4 0.62-0.69; CI 92.1-95.5; SI 64.5-66.1; IGR 0.48-0.54.

Queen
Baroni Urbani and de Andrade (2003) - Differing from the worker in the following details: eyes large but smaller than in silaceum, about 1/4 of the head length, composed by many facets and with ocular pilosity. Ocelli well developed.

Mesosoma robust and gently convex in side view. Parapsidal furrows marked. Scutellum with the sides converging posteriorly and with the posterior border subtruncate. Scutellum with a longitudinal ruga, the ruga sometimes prolonging only to the posterior half of the mesonotum but very superficial. Metanotum with a small tooth. Basal face of the propodeum almost flat laterally and concave medially.

Fore wings of our type 4, hind wings of our type 3 as defined in the description of the genus.

Colour. As in the worker but with a dark brown macula on the posterior part of the head, on the mesosoma and on the postpetiole.

Measurements in mm and Indices: TL 3.20-3.45; HL 0.63-0.68; HW 0.62-0.65; EL 0.15-0.17; SL 0.41-0.44; WL 0.90-0.98; PeL 0.20-0.22; PeW 0.31-0.35; HFeL 0.48-0.54; HTiL 0.40-0.43; HBaL 0.31-0.35; LS4 0.35-0.42; LT4 0.69-0.85; CI 95.6-98.4; SI 64.7-65.1; IGR 0.47-0.51.

Male
Baroni Urbani and de Andrade (2003) - Head slightly broader than long. Vertex in full face view broadly convex. Vertexal margin superficially carinate. Clypeus reduced, truncate and slightly longer than the antennal sockets. Frontal carinae thin, low and parallel. Frontal area with a subround tumulus anteriorly, concave posteriorly, the concavity convergent posteriorly. Ocelli large. Compound eyes large and placed mostly on the anterior part of the head sides. Scapes short of the anterior ocellus posteriorly. First funicular joint subequal to the second joint. Joints 2-12 longer than broad. Last funicular joint as long as or slightly shorter than the sum of joints 9-11. Mandibles edentate and only with a pointed apical tooth. Palp formula 5,2.

Mesosoma robust and convex in side view. Pronotum and anterior third of mesonotum almost perpendicular to the posterior two thirds of the mesonotum. Parapsidal furrows marked. Scutellum in side view convex; posterior border of scutellum round; dorsum of scutellurn with a longitudinal carina prolonging up to the mesonotum. Basal face of the propodeum weakly declivous and medially with a superficial incision prolonging to the anterior part of the declivous face. Sides between the basal and declivous faces of the propodeum subangulate. Declivous face of propodeum flat. Metanotum with a median, broad, spiniform tooth. Lower part of the propodeal lobes obtuse and upper part round and partially lamelliform. Propodeal spiracles small.

Petiole in side view with declivous anterior face, the node more convex and less scale-like than in silaceum,. Anterior border of the petiole laterally weakly marginate. Subpetiolar process small, triangular. Postpetiole anteriorly broader than the petiole; postpetiolar sides convex. Anterior border of the postpetiolar sternite with a superficial triangular "lip". Gastral tergite I convex in side view. Gastral sternite I large. Remaining gastral tergites and sternites weakly curved ventrally.

Legs as in the worker but more elongate. Hind basitarsi slightly shorter than hind tibiae.

Fore wings of our type 4, hind wings of our type 3 as defined in the description of the genus.

Sculpture. Head and mesosoma minutely and superficially reticulate-punctate and with short, irregular rugosities, the rugosities sometimes absent on the anterior half but marked and longitudinal on the posterior half of the mesonotum, the reticulation broader on the basal face of the propodeurn. Petiole, postpetiole and gaster smooth and with minute piligerous punctures. Legs smooth and minutely punctate.

Pilosity as in the worker but with the hairs of type (1) less dense.

Colour. Black with slightly lighter legs, antennae and mandibles.

Measurements in mm and Indices: TL 2.67-2.97; HL 0.50-0.55; HW 0.51-0.56; EL 0.24-0.28; SL 0.25-0.27; WL 0.86-1.00; PeL 0.19-0.20; PeW 0.22-0.25; HFeL 0.50-.057; HTiL 0.39-0.44; HBaL 0.35-0.40; LS4 0.35-0.41; LT4 0.60-0.70; CI 101.8-105.9; SI 48.1-5 1.0; IGR 0.57-0.59.

Type Material
District of Columbia, USA. Type material: two syntype workers labelled: "Corcoran Hill, D.C., July 26-9, no. 175, Proceratium crassicorne, n. sp.", in ; ten workers same data as the syntypes and probably belonging to the type series, but not examined by Emery, 2 workers in and 7 workers in  (all USNM pins labelled as Cotypes no. 53577), examined.