Prenolepis imparis ( Say, 1836 )

Williams, Jason L., 2016, Taxonomic revision and phylogeny of the ant genus Prenolepis (Hymenoptera: Formicidae), Zootaxa 4200 (2), pp. 201-258 : 222-227

Prenolepis imparis ( Say, 1836)

( Figs 72–82 )

Formica imparis Say, 1836: 287 (q. m.). Syntype queen(s?) and male(s?), (no specific locality provided) (depository unknown) [not examined]; Wheeler, 1930a: 16 (w.). Syntype worker(s?), (no specific locality provided) (depository unknown) [not examined]. Wheeler & Wheeler, 1953: 142 (l.); Hauschteck, 1962: 219 (k.). Combination in Prenolepis: Mayr, 1886: 431 . Prenolepis nitens americana Forel, 1891: 94 (m.). Syntype male(s?), UNITED STATES: (no specific locality provided) (depository unknown) [not examined]. Synonymy by Emery, 1893a: 635; Dalla Torre, 1893: 178 (here confirmed).

Formica wichita: Buckley, 1866: 169 (w.). Syntype worker(s?), UNITED STATES: (no specific locality provided) (depository unknown) [not examined]. Synonymy by Dalla Torre, 1893: 178; Wheeler, 1930a: 15 (here confirmed).

Prenolepis imparis minuta Emery, 1893a: 636 (w. m.). 3 syntype workers, UNITED STATES: District of Columbia, 1.iv.1888 ( MSNG: CASENT0905673) [examined]; ( MCZC: MCZ-ENT00025592) [examined]. Syntype male(s?), (no specific locality provided) (depository unknown) [not examined]. Synonymy by Creighton 1950: 414 (here confirmed).

Prenolepis imparis pumila Wheeler, 1930a: 21 (w. m.). 2 syntype workers, UNITED STATES: North Carolina, Raleigh ( MCZC: MCZ-ENT00021680) [examined] . 1 syntype male, same locality as syntype workers ( MCZC: MCZ- ENT 00021680 ) [examined] . 2 syntype males, North Carolina, Raleigh ( MCZC: MCZ-ENT00543330) [examined]. Synonymy by Creighton 1950: 414 (here confirmed).

Prenolepis imparis testacea Emery, 1893a: 636 (q. m). Syntype queen(s?) and male(s?), UNITED STATES: (no specific locality provided) (depository unknown) [not examined]. Wheeler , 1905: 390 (w.) . 4 syntype workers, UNITED STATES: District of Columbia ( MCZC: MCZ-ENT00025593). Synonymy by Creighton 1950: 414 (here confirmed).

Prenolepis imparis californica Wheeler, 1930a: 23 (w. q. m.). 10 syntype workers, UNITED STATES: California, Stanford University ( MCZC: MCZ-ENT00543319, MCZ-ENT00543321, MCZ-ENT00021677) [examined] . Syntype queen, same locality as syntype workers ( MCZC: MCZ-ENT00543320) [examined] . Syntype male, same locality as syntype workers ( MCZC: MCZ-ENT00021677) [examined]. Synonymy by Wheeler & Wheeler, 1986: 14 (here confirmed).

Prenolepis imparis arizonica Wheeler, 1930a: 22 (w. q. m.). 4 syntype workers, UNITED STATES: Arizona, Ramsey Canyon ( MCZC: MCZ-ENT00021676) [examined] . 1 syntype queen and 3 syntype males, same locality as syntype workers ( MCZC: MCZ-ENT00543315) [examined]. syn. nov.

Prenolepis imparis colimana Wheeler, 1930a: 24 (w.). 18 syntype workers, MEXICO: Volcan de Colima ( MCZC: MCZ- ENT 00543322 , MCZ-ENT00543323, MCZ-ENT00543324, MCZ-ENT00543325, MCZ-ENT00543326, MCZ- ENT 00021678 ) [examined]. syn. nov.

Prenolepis imparis coloradensis Wheeler, 1930a: 22 (w.). 17 syntype workers, UNITED STATES: Colorado, Cheyenne Mt. ( MCZC: MCZ-ENT00021679, MCZ-ENT00543327, MCZ-ENT00543328, MCZ-ENT00543329) [examined]. syn. nov.

Prenolepis imparis veracruzensis Wheeler, 1930a: 24 (w.). Holotype worker, MEXICO : Veracruz, Maltrata Altaluz , 05.x.1924 ( MCZ: MCZ-ENT00021681) [examined]. syn. nov.

Worker diagnosis. Obtusely angled propodeum with flat dorsal and posterior faces ( Fig 19 ); entire cuticle smooth and shiny; ectal surface of mandibles with deep longitudinal striations.

Most similar species. P. nitens

Morphology. Worker. Measurements (n=105): CMC: 16–18; EL: 0.23–0.33; EW: 0.19–0.24; HL: 0.74–0.98; HLA: 0.43–0.48; HLP: 0.25–0.34; HW: 0.71–0.98; IOD: 0.48–0.57; LF1: 0.22–0.29; LF2: 0.11–0.15; LHT: 1.01– 1.15; MMC: 1–5; MTW: 0.40–0.52; MW: 0.24–0.36; PDH: 0.28–0.39; PMC: 3–6; PrCL: 0.41–0.52; PrCW: 0.26– 0.33; PrFL: 0.78–0.98; PrFW: 0.17–0.21; PTH: 0.37–0.42; PTL: 0.33–0.40; PTW: 0.24–0.34; PW: 0.48–0.61; SL: 0.88–1.22; TL: 2.94–4.51; WF1: 0.06–0.09; WF2: 0.06–0.08; WL: 0.95–1.42; BLI: 122–153; CI: 90–101; EPI: 140–179; FLI: 185–208; HTI: 120–133; PetHI: 121–130; PetWI: 83–90; PrCI: 58–70; PrFI: 20–24; REL: 27–35; REL2: 28–36; REL3: 46–59; SI: 115–140.

Light to dark brown with head and gaster sometimes darker than mesosoma; entire cuticle smooth and shiny; abundant decumbent setae on scapes and legs; erect macrosetae on head, mesosoma, and gaster; head about as broad as long and square in shape with rounded posterolateral corners and a straight posterior margin; compound eyes moderately large and convex, but do not surpass the lateral margins of the head in full-face view; torulae overlap with the posterior border of the clypeus; anterior border of clypeus with a pair of prominent anterolateral lobes ( Fig 42 ); mandibles with 5–7 teeth (usually 6) on the masticatory margin; ectal surface of mandibles with deep longitudinal striations; in profile view, propodeum is obtusely angled with a flat dorsal face ( Fig 19 ); dorsal apex of petiole scale is sharply angled and forward-inclined ( Fig 53 ).

Queen. Measurements (n=9): EL: 0.42–0.48; HL: 1.26–1.44; HW: 1.38–1.55; SL: 1.36–1.55; TL: 7.05–8.33; WL: 2.49–3.08; BLI: 175–199; CI: 105–117; REL: 31–38; REL2: 30–34; SI: 97–103.

Much larger and distinctly lighter in color than male; light to medium brown; abundant short, erect macrosetae on head, mesosoma, and gaster; entire cuticle covered in dense pubescence; head broader than long and square in shape; three ocelli present; compound eyes large and convex, barely surpassing the lateral margins of the head in full-face view; antennae with 12 segments; scapes long, surpassing the posterior margin of the head; mandibles with 6 teeth on the masticatory margin; ectal surface of mandibles with longitudinal striations; mesosoma large to accommodate flight muscles and without a constriction; small collar-like pronotum; large and strongly convex shelf-like mesonotum; petiole is forward-inclined and triangular, as seen in worker; dorsal apex of petiole scale is sharply angled.

Male. Measurements (n=10): EL: 0.31–0.45; HL: 0.66–0.82; HW: 0.72–0.89; SL: 0.54–0.75; TL: 3.16–4.16; WL: 1.30–1.65; BLI: 165–191; CI: 102–110; REL: 47–57; REL2: 43–54; SI: 75–89.

Much smaller and distinctly darker than queen; dark brown; abundant long, erect macrosetae on head, mesosoma, and gaster; entire cuticle covered in dense pubescence; head broader than long and oval in shape; three large ocelli present; compound eyes very large and convex, surpassing the lateral margins of the head in full-face view; antennae with 13 segments; scapes very short, barely surpassing the posterior margin of the head; mandibles with a single apical tooth on the masticatory margin; ectal surface of mandibles with longitudinal striations; mesosoma large to accommodate flight muscles and without a constriction; small collar-like pronotum; large and strongly convex shelf-like mesonotum; petiole is forward-inclined and triangular, as seen in worker; dorsal apex of petiole scale is sharply angled; genitalia oriented ventrally; parameres elongate, roughly triangular, and curved medially; ental surface of parameres flattened; digiti are long and slender and follow the penis valve as it curves ventrally; cuspi are broad, triangular, and very short relative to the rest of the genitalia; parameres are covered in dense very long, erect macrosetae; edges of cuspi are covered in short, erect macrosetae; 9th sternite is large and broad.

Notes. This species bears a strong morphological resemblance to P. nitens but has a different distribution and a more slender mesosoma at the mesonotal constriction ( Fig 19 ). Several key differences can also be seen in male genitalia between P. imparis and P. nitens (see notes under P. nitens ).

This species has a wide distribution and shows high morphological variation in the worker caste. As a consequence, many synonyms have been created with descriptions based on variation in color, size, and minor differences in propodeum shape. We treat them here as all being a single species with a high degree of intraspecific variation. Examination of male external genitalia from across the range revealed no notable differences.

Microgynous queens were observed by Alex Wild (personal communication, September 9, 2015) in the Sierra Nevadas, California in October, 2001. Two specimens were collected by Wild, one of which was examined for this study (USNMENT00755072). The other can be found on www.AntWeb.org (CASENT0005430). These queens appear to be P. imparis , but are much smaller and were observed flying in the fall rather than early spring. While it is possible that this is an entirely new species, perhaps even an inquiline, based on its size, it is also possible that these individuals are microgynous ( Rüppell & Heinze 1999) P. imparis queens. With only two specimens available and little morphological difference from P. imparis observed more evidence must be found in order to describe them as a new species.

Other material examined. Specimens from hundreds of localities across the United States and Mexico.

Figures

FIGURES 72 – 74. Prenolepis imparis worker USNMENT 00755082. Lateral, full-face, and dorsal view of the body.

FIGURES 75 – 82. Prenolepis imparis reproductives. 75, queen in frontal view; 76, queen in lateral view; 77, male in frontal view; 78, male in lateral view; 79 – 82, male genitalia (dorsal, ventral, ventral close-up of digitus and cuspus, and lateral parameres).

FIGURES 15 – 27. Illustrations of mesosoma shapes (profile view) observed in all Prenolepis species. 15, P. angularis; 16, P. darlena; 17, P. fisheri; 18, P. fustinoda; 19, P. imparis; 20, P. jacobsoni; 21, P. jerdoni; 22, P. mediops; 23, P. melanogaster; 24, P. naoroji; 25, P. nitens; 26, P. shanialena; 27, P. subopaca.

FIGURES 38 – 50. Illustrations of clypeus shapes (full-face view) observed in all Prenolepis species. Apparent differences in width of torulae are artifacts of specimen orientation. In some species the torulae are oriented more laterally. 38, P. angularis; 39, P. darlena; 40, P. fisheri; 41, P. fustinoda; 42, P. imparis; 43, P. jacobsoni; 44, P. jerdoni; 45, P. mediops; 46, P. melanogaster; 47, P. naoroji; 48, P. nitens; 49, P. shanialena; 50, P. subopaca.

FIGURES 51 – 56. Illustrations of petiole shapes (profile view) observed in Prenolepis species. 51, P. darlena; 52, P. fustinoda; 53, P. imparis (typical shape seen in most Prenolepis species); 54, P. jacobsoni; 55, P. jerdoni; 56, P. subopaca.