Strumigenys pilinasis Forel 1901

Booher, Douglas B., 2019, Taxonomic clarification of two Nearctic Strumigenys (Hymenoptera: Formicidae), Zootaxa 4664 (3), pp. 401-411 : 402-405

Strumigenys pilinasis Forel 1901

( Figure 1 )

Strumigenys clypeata var. pilinasis Forel 1901 , 45:339. Lectotype worker (here designated from a unique syntype): Washington, D.C. (Forel) [MHNG, CASENT0909339, AntWeb.org image examined]. Raised to species: Wesson & Wesson, 1939: 109. In Strumigenys (Cephaloxys) : Emery, 1924: 325; in Strumigenys (Trichoscapa) : Smith, 1947: 587; in Smithistruma: Smith, 1951: 827 ; Brown, 1953: 60; in Pyramica: Bolton, 1999: 1673 ; in Strumigenys: Baroni Urbani & De Andrade, 2007: 126 .

Strumigenys ohioensis Kennedy & Schramm, 1933: 98 , figs. 1, 2. Holotype worker: Ohio, Miegs County, Tuppers Plains (Schramm) [MCZC, examined]. Description of queen, male: Brown, 1953: 87. In Strumigenys (Cephaloxys) : Wesson & Wesson, 1939: 108; in Strumigenys (Trichoscapa) : Smith, 1947: 587; Creighton, 1950: 308; in Smithistruma: Smith, 1951: 828 ; Brown, 1953: 87; in Pyramica: Bolton, 1999: 1673 ; in Strumigenys: Baroni Urbani & De Andrade, 2007: 125 . New Synonym.

Strumigenys (Cephaloxys) manni Wesson & Wesson, 1939: 97 , pl. 3, fig. 3. Holotype worker: Ohio, Pike County, near Sinking Spring [MCZC, examined]. Junior synonym of ohioensis: Smith, 1951: 828 ; Brown, 1953: 87. New Synonym.

Diagnosis. Strumigenys pilinasis is one of the most easily diagnosed Nearctic Strumigenys and can be distinguished from all other North American species by the unique clypeal pilosity. Strumigenys pilinasis is the only species with simple coarse hairs extending from the lateral border of clypeus that are strongly J-shaped ( Figure 1a ). These hairs, although variable, have several to many inclined anteriorly at their bases, strongly curved along their mid-length, and directed posteriorly at their apices. These hairs are simple and coarse to extremely narrowly expanded, always more cylindrical than spatulate along their entire length. The brief description given below is in agreement with descriptive treatments of the junior synonyms S. ohioensis and S. manni ( Kennedy and Schramm 1933, Wesson & Wesson 1939, Bolton 2000).

Lectotype measurements. Measurements taken from images (AntWeb 2019).

HL = 0.577; HW = 0.400; ML = 0.123; PW = 0.280; SL = 0.297; TL = 2.120;

WL = 0.581; CI = 69; MI = 21; SI = 74.

Description. Head. Mandibles with basal broad triangular lamella, half of which is concealed by clypeus and half is visible in full frontal view; lamella followed by five principle teeth; counting from base of mandible tooth one, two, and four similarly sized and smaller than tooth three; tooth five as long or longer than first two teeth; tooth three being obviously longer than any other tooth. Clypeus slightly wider (0.223) than long (0.210) and narrowing anteriorly toward mandibles; nearly equal in width as distance between mandible insertions; anterior border between mandible insertions convex. Scape narrow and not expanded at subbasal bend; sharply bent just above condyle forming nearly a 90° angle. Scape nearly ¾ the width of head (SI = 74). Mesosoma in profile pronotum and mesonotum broadly convex; metonotal groove weakly impressed to absent; propodeum flat. Propodeal spine triangular and well formed (ca. 0.055 mm long) followed ventrally by a narrowing lamella along the declivitous face of propodeum.

Sculpture. Clypeus and head heavily punctate to reticulopunctate. Dorsum and side of pronotum with reticulopunctate sculpture similar to that on dorsum of head. Most of the side of mesonotum, pleurae, and propodeum shining with peripherally punctate sculpture. Dorsum of petiole with reticulopunctate sculpture, disc of postpetiole smooth and shining. Basigastral costulae well developed and extending nearly one third of the length of the first gastral tergite. The rest of the abdomen smooth and shining.

Pilosity. Hairs on lateral margins of clypeus J-shaped and pointing posteriorly at apices. Hairs on anterior margins variable and tending to curve ventrally. Hairs on clypeal dorsum variably oriented, but tending to arch anterolaterally, extending anteriorly at their base and curving laterally to posterolaterally along midlength. Hairs on scape similar in shape to clypeal dorsum and variably directed with some hairs directed toward base of scape, some directed ventrally, but most hairs arched anterolaterally and directed towards apex of scape. Head, mesosomal dorsum, dorsum of petiolar node, and exposed disc postpetiole with abundant arched coarse to narrowly expanded hairs. On the dorsum of head, these hairs are directed medially and on petiolar and postpetiolar nodes they are directed posteriorly. Differentiated elongate to flagellate hairs at humeral angles and basitarsi present and apparent in most non-type specimens, not apparent on type images. However, these hairs are easily abraded and are often missing and in the case of the type specimen the excess of glue covering the basitarsi obscure examination and are not important diagnostic characters for S. pilinasis .

Comments. Strumigenys pilinasis is a common eastern North American litter-dwelling ant that has been collected in contiguous states between Connecticut and Florida and west to eastern Texas and Oklahoma. Throughout its range, unlike S. brevisetosa , pilosity and morphology vary little—making it easily identifiable across its range. Of 9,013 databased records of Nearctic Strumigenys , in a database maintained by the author, S. pilinasis ranked fourth with 646 specimen records (unpublished data). In two studies of Strumigenys found nesting in empty fallen nuts in forests near Washington D.C. (near lectotype collection), S. pilinasis was by far the most common species ( Duffield & Alpert 2011, Booher et al. 2017).

Kennedy and Schramm provided an inaccurate illustration of S. ohioensis . They described and illustrated hairs projecting from the lateral borders of the clypeus that were relatively short and directed anteriorly, when in fact these hairs are variable and several to many are strongly J-shaped—being inclined anteriorly at their bases, strongly curved along their mid-length, and point posteriorly at their apices. In 1939, Wesson & Wesson described S. manni (new junior synonym S. pilinasis ) and it was the first description to accurately describe the key and unique distinguishing character of this species, the J-shaped clypeal pilosity. However, Wesson & Wesson did not realize S. manni was synonymous with S. ohioensis because they did not examine the type specimens of S. ohioensis and only relied on the original description and illustrative work ( Kennedy and Schramm 1933). Brown (1953) provided greater detail and a full accounting of this set of events when he listed S. manni as a junior synonym of S. ohioensis , but Brown did not examine the S. pilinasis holotype ( Brown 1953).

Figures

FIGURE 1. Holotype worker of Strumigenys pilinasis [MHNG: CASENT0909339] Photographed by Zach Lieberman, Ant- Web.org.