Crematogaster nigropilosa Mayr

Longino, J. T., 2003, The Crematogaster (Hymenoptera, Formicidae, Myrmicinae) of Costa Rica., Zootaxa 151, pp. 1-150 : 94-97

Crematogaster nigropilosa Mayr 1870

Plate 1, 5

Crematogaster nigropilosa Mayr , 1870a:405. Syntype workers: Colombia, Santa Fe de Bogota (Lindig) [ NMW] (examined). Mayr, 1887:624: description of queen from Santa Catarina, Brazil. Emery, 1922:136: combination in C. (Orthocrema) .

Range

Nicaragua to Bolivia, Brazil.

Description of worker (Costa Rica)

Color dark red brown to black.

Mandibles smooth and shiny; in full face view anterior margin of clypeus weakly convex; clypeus convex, shiny, with 4-5 thin longitudinal carinulae; face smooth and shiny; scapes with longitudinal carinulae and faint etching, subopaque, with a combination of abundant subdecumbent setae and abundant long erect setae, erect setae much longer than width of scape; terminal 4-5 segments of antenna gradually lengthening to form club, becoming increasingly densely pubescent, terminal two segments the largest and most conspicuous; face with abundant erect amber to black setae, often forming a dense brush on face; in full face view with a crown of dark setae projecting from sides and posterior margin of head posterior to eyes, sparse short curved setae projecting from sides of head anterior to eyes; ventral surface of head with sparse suberect setae.

In lateral view, pronotum rising above anterior collar to gently convex dorsal surface, mesonotum flat, strongly sloping, with anteriorly raised boss and well developed anterolateral tubercles, relatively long such that pronotum elevated above propodeum; propodeal suture deep medially, appearing shallow in lateral view because of pronounced lateral carinae that bridge suture; dorsal face of propodeum horizontal, well differentiated from and about as long as sloping posterior face; propodeal spines very large, broadly triangular at base, gradually tapering to outermost seta, beyond which spine more abruptly tapers to long, acute tip (size of spine beyond outermost seta highly variable); side of pronotum smooth and shiny; anepisternum smooth and shiny; katepisternum smooth and shiny medially, with microareolate sculpture around margins; side of propodeum smooth and shiny dorsally, faintly rugulose and microareolate ventrally; pronotal dorsum with about 7 thin longitudinal carinulae, interspaces smooth and shining; mesonotum with strong lateral carinae, converging posteriorly, medial space smooth and shining; dorsal face of propodeum with carinulae that are longitudinal anteriorly, sweep outward onto bases of propodeal spines, several curved transverse carinulae between spines at juncture of dorsal and posterior faces (specimens from the Osa Peninsula have weaker sculpture overall, pronotal carinulae nearly absent, dorsal and lateral faces of propodeum largely smooth and shining); posterior face smooth and shining; setae on mesosomal dorsum long, stout, blackish, on average 4 on anterior pronotum, 2 on anterior mesonotum, 2 (shorter) on posterior mesonotum, 2 on base of each propodeal spine, with variation of plus or minus a seta at each position; legs with abundant suberect pubescence/short pilosity, no long erect setae.

Petiole in side view trapezoidal, smooth and shiny or with faint microareolate sculpture; anteroventral tooth small but usually distinct, forming a right to obtuse angle; dorsal face elongate, tapering anteriorly, smooth and shiny or faintly microaerolate, with two long dark setae on each posterolateral tubercle; postpetiole with no ventral tooth, postpetiole in dorsal view globular, well separated from petiole by cylindrical anterior peduncle; fourth abdominal tergite smooth and shining; postpetiole and fourth abdominal tergite with abundant long erect dark setae.

Measurements

HL 0.716, 0.631, 0.814; HW 0.747, 0.653, 0.864; HC 0.680, 0.606, 0.810; SL 0.848, 0.709, 0.958; EL 0.160, 0.160, 0.182; A11L 0.334; A11W 0.124; A10L 0.171; A10W 0.113; A09L 0.081; A09W 0.080; A08L 0.070; A08W 0.067; WL 0.904, 0.731, 1.078; SPL 0.332, 0.242, 0.318; PTH 0.227, 0.158, 0.258; PTL 0.384, 0.301, 0.394; PTW 0.202, 0.154, 0.240; PPL 0.248, 0.178, 0.243; PPW 0.235, 0.199, 0.302; CI 104, 103, 106; OI 22, 25, 22; SI 118, 112, 118; PTHI 59, 53, 65; PTWI 53, 51, 61; PPI 95, 112, 124; SPI 37, 33, 29; ACI 1.60.

Queen (Costa Rica)

A normal queen (dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum, Fig. 1); head pilosity and sculpture characters as in worker; terminal 4 segments of antenna gradually enlarging to form club, the last two largest and most conspicuous; pronotal dorsum short, perpendicular, forming curving obtuse to sharp right angle with anterior collar, recessed beneath bulging mesonotum; propodeal spine broadly conical, short, with acute tip, 0-1 setae on side of propodeum anterior to spine; dorsal mesonotum and scutellum with abundant erect setae; tibiae with scattered long erect setae (in contrast to workers); petiole in lateral view similar to worker but more robust, shorter and taller; dorsal face of petiole subquadrate, sides straight to slightly convex, longer than wide, abruptly constricted anteriorly to narrow peduncle; postpetiole with no ventral tooth, in dorsal view subtrapezoidal, wider than long, widest anteriorly; postpetiole with abundant long setae of variable length; fourth abdominal tergite with even vestiture of abundant, stiff, moderate length erect setae; size characters as in Figures 4 and 5.

Biology

Crematogaster nigropilosa occurs in a wide variety of habitats and elevations, with the exception of extremely dry areas. It is common in low to mid elevation rainforests, and may be found in moist microhabitats in seasonally dry areas. Although most abundant at low to middle elevations, it also can occur at high elevation cloud forest sites where virtually no other ants are found. I collected a worker in a Winkler sample at 2400m elevation on Volcan Barva in Costa Rica, and Peck collected the species at 2600m in Chiriquí province, Panama.

Nests are often in soft bits of dead wood or small hollow plant stems. The nests are usually on the forest floor or within a few meters of the forest floor in shaded areas and understory. I have also seen nests in rotten stumps, in chambers in rotting walls of abandoned houses in rainforest, and occasionally in internodes of Cecropia saplings. Nests contain a worker population ranging from a few dozen to about 300. Ergatogynes are very common. Nests exhibit a range of reproductive structures. Some have a standard complement of workers, brood, and one colony queen. Others have the colony queen plus one or more ergatogynes. An example is a colony I collected in its entirety from two adjacent internodes of a Cecropia sapling. The colony contained one dealate queen, 28 alate queens, 11 adult males, 13 ergatogynes, 324 workers, and brood. Nests may be queenless, containing only workers, brood, and one or more ergatogynes. Often these queenless nests appear to be the only nest in the vicinity, with no indication of being part of a polydomous colony. Although most of the nests I have observed have been monogynous or lacking a queen, one nest collection from Venezuela was polygynous. A lab colony kept for about one year was comprised of workers and one ergatogyne. The colony continually produced males as the worker population gradually declined to extinction. Thus a queenless colony fragment is at least able to produce males.

Foragers may be found day or night. They occur on extrafloral nectaries and have been taken at tuna baits on the ground.

Comments

The combination of very long, divergent propodeal spines and appressed tibial setae uniquely identify this species. Crematogaster longispina has similar large spines, but the pilosity on the tibiae is erect.