Strumigenys lucky, 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 : 227-230

Strumigenys lucky sp. nov.

Figure 38

Distribution. USA; Illinois, Iowa, Minnesota, and Wisconsin.

Holotype worker. USA, Minnesota, Houston Co.: Winnebago Creek , 31 May 1941, Collectors Jerry L. Cook & J. B. Martin (colony 275), bottom specimen mounted on pin with pinned identifier code ( MCZC-ENT 00683064 )[ MCZC].

Paratypes. Three workers and two queens from the same colony (colony 275) all with same collections data as type; one worker, top specimen mounted on same pin as type (MCZC-ENT00683064)[ MCZC]; two workers mounted on the same pin (MCZC-ENT00683065) [ MCZC]; two dealate gynes (MCZC-ENT00683066, MCZC-ENT 00683067 ) [ MCZC] .

Holotype and paratype measurements (n=4): HL = 0.531 –0.562 (0.546); HW = 0.394–0.41 (0.402); ML = 0.097–0.1 (0.099); PW = 0.264 –0.273 (0.269); SL = 0.261 –0.299 (0.281); FL = 0.355 –0.399 (0.369); HT = 0.294 – 0.318 (0.31); EL = 0.033 –0.051 (0.044); WL = 0.557 –0.584 (0.568); CI = 72.4–75.1 (73.7); MI = 17.3–18.6 (18); SI = 66.1–74.4 (69.9).

Paratype queen measurements (n=2): HL = 0.594 –0.598 (0.596); HW = 0.432 –0.433 (0.433); ML = 0.092 – 0.109 (0.101); PW = 0.325 –0.339 (0.332); SL = 0.299 –0.308 (0.304); FL = 0.351–0.41 (0.381); HT = 0.344 –0.352 (0.348); EL = 0.117 –0.121 (0.119); WL = 0.674 –0.693 (0.684); CI = 72.2–72.9 (72.6); MI = 15.4–18.4 (16.9); SI = 69.2–71.1 (70.2).

Diagnosis. Of species occurring in the western USA, only four have spatulate to spoon-shaped setae on the free margins of the clypeus curving away from the midline, S. reflexa , S. missouriensis Smith, 1931 , S. pulchella Emery, 1895 , and S. lucky . Strumigenys lucky is most morphologically similar to S. missouriensis (I believe to be a complex of species requiring taxonomic treatment) but can be separated from the S. missouriensis complex by head pilosity. Strumigenys lucky has long flagellate hairs at apicoscrobal position and at the vertex margin of head. In S. missouriensis these hairs, if present, are shorter stiff and straight; varying in shape from simple to apically expanded; and may not be much longer than the background pilosity. Strumigenys reflexa have setae that curve away from the midline of the head at the nearest point where the outer mandibles and clypeus meet, in S. lucky and S. pulchella , these setae curve towards the midline or are directed ventrally. Strumigenys lucky can be separated from S. pulchella by teeth dentition, in S. pulchella the first two teeth are nearly equal in size with the third tooth smaller than the first two. In S. lucky , the first (excluding first denticle if present) and third tooth are nearly equal in size with the second tooth smaller.

Description of worker. Mandibles with a triangular flattened lamella that is slightly smaller in length than the first basal tooth. Basal lamella followed by a diastemmic gap that is longer than the first basal tooth. Masticatory margin with seven principle teeth followed by four evenly sized denticles and terminating with an enlarged apical tooth. Counting from base of mandible, principle teeth alternate in size with teeth two, four and six being similarly sized and smaller than teeth one, three, five, and seven. Elongate teeth one, three, five, and seven decreasing in size from tooth one to tooth seven, with tooth seven being only slightly larger than tooth six. Similar to ananeotes , some specimens have a minute denticle present before the first principle tooth. Clypeus about 1.1–1.3 times wider than long; with an extremely narrow peripheral groove with the lower anterior margin extending beyond dorsal anterior margin and visible as a narrow translucent cuticular projection in full frontal view; in full frontal view continuously convex over lateral and anterior free margins. Ventral postbuccal groove broad and shallow. Upper scrobal margin weakly marginate; terminating just past level of eye. Preocular carinae well developed with straight lateral margins; posterior portion obscured by scrobal margin in full frontal view.

Head in profile flat from vertex to clypeus. Clypeus slightly raised above area of frontal lobes with a shallowly convex area between them. Eye with 2–4 pigmented ommatidia. Scape slightly expanded past subbasal bend and narrowly marginate along anterior border. In profile, dorsal outline of pronotum and mesonotum flat, angulate at their junction; propodeum weakly convex and separated from mesonotum by a shallow and slightly impressed metanotal suture. Propodeal teeth lamellate, pointed, and broadly triangular; subtended by an uneven lamella, narrowing strongly to about midlength then expanding to a length about the same size as the propodeal tooth just above bulla of metapleural gland.

Pilosity. Elongate subflagellate, flagellate, or looped setae present at apicoscrobal position, as pair straddling the midline near the posterior margin of head, at humeral angles, straddling the central portion of pronotal dorsum, and at anterior dorsolateral corners of mesonotum. Outer surfaces of meso- and meta- tibia and basitarsi with a single flagellate seta. Two pairs of shorter subflagellate or apically looped setae present on dorsum of petiolar node, three pair present on exposed disc of postpetiole, and three to four rows of 1–3 pairs of setae on first gastral tergite.

Clypeus with lateral border fringed with three to four pairs of spatulate setae that curve ventrally; anterior border between mandible insertions with a pair of similar setae that curve away from the midline. Setae on dorsum of clypeus are shorter than those on anterior margin, slightly less expanded, and with most directed laterally away from the midline of head; setae closer to lateral margins curve away from the midline and those located more centrally tend to curve posteriorly towards the back of head. Setae on dorsum of head spatulate at apices; longer and more shallowly curved than those on the dorsum of clypeus; directed towards the midline; those anterior to vertex are more expanded at apices than those posterior to vertex. Setae along upper anterior scrobal margin narrowly spatulate at apices; seta at subbasal bend longest and directed anteriorly away from anterior margin of scape the one or two setae following this seta curve towards base; all other setae curve towards apex of scape. Mesosoma ground pilosity limited to a few short reclinate simple setae on the pronotum. Shorter evenly curved simple setae cover surface of petiolar node and legs, ground pilosity absent from exposed disc of postpetiole and first gastral tergite.

Sculpture. Clypeus and head reticulopunctate with a small smooth patch in frontal area between frontal lobes; scrobal area reticulopunctate. Dorsum of mesosoma punctate without a distinct medial carina. Sculpture on declivitous face of propodeum limited to weakly reticulopunctate sculpture on upper half. Anterior edge of metanotal suture with a thin transverse cuticular ridge. Surface of petiolar node reticulopunctate. Petiolar node punctate. Exposed disc of postpetiole without sculpture and shining. First gastral tergite with basigastral costulae extending between 1/4 to 1/3 the length of the first gastral tergite and without any other sculpture.

Spongiform appendages. Spongiform cuticular processes well developed; as a lateral process on petiolar node; as a ventral curtain of peduncle of petiole that is shallowly to deeply impressed medially; 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 that is usually at least twice as deep as the maximum length of exposed disc in profile view.

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, can be diagnosed by dentition and clypeal pilosity, and can be keyed out.

Etymology. Named after midwestern-born myrmecologist Andrea Lucky to recognize the contributions she has made to myrmecology, for her integration of citizen science into fundamental research, for being a strong advocate for women in myrmecology, and as an award-winning teacher and student mentor. The name ‘lucky’ is given as a proper noun in the nominative case used in apposition. The orthography of an eponym is unchangeable and does not depend on the generic name in which the epithet is used.

Comments. This species has the most northern range of any Nearctic species and is known from a few collections taken in four neighboring states (Wisconsin, Minnesota, Illinois, and Iowa). However, in at least one locality (in Waukesha, Wisconsin), this species has been collected multiple times by young myrmecologist Anthony Prothero who provided the only natural history account of S. lucky in personal communications. Prothero found them in a ‘forest’ which used to be a prairie. The forest is almost completely dominated by invasive Buckthorn trees, but random clearings hold many prairie plants. He has located several partial colonies of a few workers and an occasional queen, always under rocks and most commonly during or recently after rain. He expects they are nesting in soil cavities beneath rocks or other debris. The soil in these areas is mostly silt/clay mix.

This species has been misidentified as S. missouriensis , likely due to similarities of clypeal pilosity and shape, for this reason and because they overlap in the eastern portion of S. lucky’ s range I have included S. missouriensis in the key but not the synopsis of species in the western region.

Nontype material examined: two workers mounted on same pin, USA, Illinois, Cook Co.: Sag Canal Area , spring 1954, Collectors H. S. Dybas & C. H. Seevers, specimen identifier (MCZC-ENT00683071) [ MCZC] ; one worker, USA, Iowa, Story Co.: Ames, 16 Apr 1941, Collector W. F. Buren, unique specimen identifier ( MCZC-ENT 00683068 ) [ MCZC] ; one worker, USA, Iowa, Story Co.: Ames, 20 Apr 1940, Collector W. F. Buren, unique specimen identifier (MCZC-ENT00683070) [ MCZC] .

Nontype worker measurements (n=4): HL = 0.521 –0.553 (0.538); HW = 0.395 –0.403 (0.400); ML = 0.094– 0.11 (0.100); PW = 0.253 –0.275 (0.264); SL = 0.258 –0.293 (0.280); FL = 0.335 –0.357 (0.348); HT = 0.296 –0.307 (0.303); EL = 0.035 –0.045 (0.042); WL = 0.526 –0.565 (0.541); CI = 72.3–75.8 (74.3); MI = 17.2–19.9 (18.6); SI = 64–73.3 (70.1).

Figures

FIGURE 38. Holotype worker of Strumigenys lucky [MCZC: MCZC-ENT000683064 (bottom specimen)]. Photographed by Michele Esposito (AntWeb.org 2021).