Strumigenys macgowni, Booher, 2021

Booher, Douglas B., 2021, The ant genus Strumigenys Smith, 1860 (Hymenoptera: Formicidae) in western North America North of Mexico, Zootaxa 5061 (2), pp. 201-248 : 230-233

Strumigenys macgowni sp. nov.

Figure 39

Distribution. USA; in eastern USA occurs in Louisiana; in western USA occurs in Texas.

Holotype worker: USA, Texas, San Jacinto County, Big Creek Scenic Area , 30.51966 -95.08816 ± 1000 m, 16 October 1997, 80 ± 5 m, Collectors Jerry L. Cook & J. B. Martin (unique specimen identifier casent0747540) [ UGCA].

Paratype queen: Same as worker (unique specimen identifier casent0747059)[ CAS]

Holotype worker measurements: HL = 0.495; HW = 0.345; ML = 0.105; PW =; SL = 0.259; FL = 0.321; HT = 0.253; EL = 0.038; WL = 0.515; CI = 69.8; MI = 21.2; SI = 74.9.

Paratype queen measurements: HL = 0.585; HW = 0.409; ML = 0.113; PW = 0.295; SL = 0.295; FL = 0.403; HT = 0.321; EL = 0.093; WL = 0.635; CI = 70.0; MI = 19.3; SI = 72.0.

Diagnosis. Strumigenys macgowni is morphologically most similar to S. talpa group members ( Bolton 2000) but is differentiated from all other members by the shape and orientation of setae on the lateral margins and dorsum of clypeus. In S. macgowni , all the setae fringing the lateral and anterior clypeal margins are narrowly spatulate and are directed anteriorly or towards the midline, those on the clypeal dorsum are short simple setae that curve abruptly above their base and are directed apically towards the head. Strumigenys not belonging to the talpa group with similar dentition and also having posteriorly directed setae on the clypeal dorsum are differentiated by having setae fringing the clypeal border directed away from the midline or mandibles ( S. wrayi ( Brown, 1950) , S. reflexa Wesson & Wesson, 1939 , S. cloydi ( Pfitzer, 1951) , S. ornata Mayr, 1887 , S. dietrichi Smith, 1931 , S. boltoni ( Deyrup, 2006) , and S. apalachicolensis ( Deyrup & Lubertazzi, 2001)) .

Description of worker. Mandibles with basal lamella fully exposed in full frontal view followed by a short diastemmic gap longer than the first tooth; with four principle teeth, tooth one, two, and four being similar in size and tooth three slightly smaller. Principle teeth followed by two teeth that are slightly smaller than third principle tooth, four minute denticles, and terminating with an enlarged apical tooth. Clypeus 1.25 times wider than long and without a peripheral groove; in full frontal view the lateral and anterior margins are evenly convex; lateral margins weakly serrated due to weakly expanded cuticular areas projecting out from base of extending setae. Dorsal surface of clypeus narrowly domed when viewed from apex of mandible to back of head. Ventral postbuccal groove broad and shallow. Upper scrobal margin terminates past level of eye. Preocular carina well-developed, lateral margin straight and visible in full frontal view along entire length. Head in profile shallowly convex from vertex to clypeus; shallowly depressed at frontal lobes; clypeus slightly raised above area of frontal lobes and shallowly convex between posterior and anterior portions. Eye with four pigmented ommatidia. Scape slightly expanded past subbasal bend with a narrowly marginate anterior border; subcylindrical in shape.

In profile, pronotum shallowly convex meeting mesonotum at a broadly convex angle; mesonotum and propodeum evenly flat in profile without a distinctly impressed metanotal suture. Bulla of propodeal spiracle small and directed posteriorly. Propodeal teeth lamellate, pointed, and broadly triangular; subtended by a narrowed even-margined lamella (no indentations or lobes) that is about half as wide (0.028), as length of tooth (0.048).

Pilosity. Elongate flagellate setae limited to those present at apicoscrobal position, a pair at humeral angles, a pair on mesonotum just anterior of metanotal suture, a pair on anterior node of petiole, a pair on the anterior exposed disc of postpetiole, and several pairs on gastral tergites. A single pair of elongate flagellate setae on meso- and metabasitarsi.

Clypeus with lateral border evenly fringed with short narrowly spatulate setae that curve anteriorly towards mandible; anterior border between mandible insertions fringed with similar but slightly smaller setae that curve ventrally. Setae on dorsum of clypeus shorter than those on anterior margin, simple to slightly expanded, and bend to curve posteriorly towards the head. Setae on dorsum of head are nearly as long as eye (~0.035) and are simple to shallowly expanded; setae arise at base and are evenly curved with apices contacting head; those anterior to vertex curve medially and those posterior vertex curve towards vertex. Setae along upper scrobal margin curve sharply at base and are directed anteriorly following scrobal margin. Other than the single pair of elongate flagellate setae at apicoscrobal position, there are no differentiated standing setae anywhere else on head. Setae on scape simple and curved towards apex of scape. Note – the first seta on the leading edge of the left scape is slightly more elongate than flanking setae and is slightly more expanded, directed anteriorly.

Mesonotum ground pilosity similar to head, but more elongate. Dorsum of propodeum without any pilosity. Nodes of petiole and postpetiole with elongate posteriorly curved setae. First gastral tergite with three or four rows of flagellate setae and with scarce pilosity similar to those on the head present but limited to the lateral borders of tergite.

Sculpture. Clypeus heavily punctate; head reticulopunctate with a small smooth patch in frontal area between frontal lobes; scrobal area reticulopunctate. Dorsum of mesonotum punctate with a medial carina that more distinct than additional striae that flank it. Dorsum of propodeum lightly punctate medially with striate sculpture running laterally from base of propodeal tooth to metanotal suture; declivitous face with similar punctate sculpture. Side of pronotum and mesonotum without sculpture. Medial portion of side of propodeum free of sculpture, some reticulopunctate sculpture along posterior margin that borders the declivitous face. Anterior edge of metanotal suture with a shallowly raised transverse ridge. Surface of petiolar node reticulopunctate. Exposed disc of postpetiole without sculpture and shining. First gastral tergite with basigastral costulae extending 1/3 of first gastral tergite and without any other sculpture.

Spongiform appendages. Spongiform cuticular processes well developed; as a lateral process on petiolar node (0.088 long and 0.062 deep); as a ventral curtain of peduncle of petiole narrowing medially (maximum depth 0.055); as a lateral lobe on postpetiole connecting with posterior and anterior fringe that completely encircles exposed disc in dorsal view; and a ventral lobe of postpetiole (0.168 deep) that is much longer than the maximum length of exposed disc in lateral view (0.028).

Queen description. Other than morphological differences associated with queen caste e.g., larger size, larger eyes, size, and presence of ocelli, the queen matches worker description and can be diagnosed by dentition and clypeal pilosity.

Etymology. Named after prominent southeastern naturalist, self-taught myrmecologist, and artist, Joseph A. MacGown. MacGown has been instrumental in helping southeastern myrmecologists identify ants, obtain natural history information, and jumpstart their scientific careers (mine included). The name was created by adding the singular Latin genitive case suffix -i to the last name of a male person. The orthography of an eponym is unchangeable and not depend on the generic name in which the epithet is used.

Comments. At present, this species is known only from a queen and worker from the type locality in San Jacinto Co., Texas and a single worker collected in Sam Houston Jones State Park, Louisiana. However, as this species is easily confused with S. talpa , there are likely more specimens of this species lurking in collections and misidentified as such. The directionality, density, and shape of dorsal clypeal pilosity has not been a focal character in previous treatments of Nearctic Strumigenys but has provided clear morphological separations among many species in this study and can easily separate S. macgowni from S. talpa . Not much is known about this ant other than basic collection information on collection labels. The type specimens from Texas were Winkler extracted from litter in October at Big Creek Scenic Area, a densely forested hardwood and pine nature preserve in east Texas. The single Louisiana worker was collected in a pitfall trap in a forested area of Sam Jones State Park.

Nontype material examined: USA, Louisiana, Calcasieu Parrish, Sam Houston Jones State Park , 1 worker, 30.51966 -95.08816 ± 1000 m, 17 August 1987, el 80 ± 5 m, Collector W. MacKay #8971 (unique specimen identifier casent0799752) [ DBBC] .

Figures

FIGURE 39. Holotype worker of Strumigenys macgowni [UGCA: casent0747540]. Photographed by Michele Esposito (Ant- Web 2021).