Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Image catalog (click here).
Range
Costa Rica to Amazonian Brazil, Peru.
Identification
This species shares most of the characters of crinosa relatives (face with sparse erect setae over short appressed pubescence, sparse erect setae on mesosomal dorsum, short upturned propodeal spines) but differs in the presence of long flexuous rather than short stiff setae on the pronotal humeri. Similar species are crinosa, torosa, rochai, and moelleri. With practice some general habitus characters differentiate it from these four. The propodeal spines are a bit thinner and longer and the size polymorphism less pronounced. The flexuous rather than stiff humeral setae differentiate it from the first three. Crematogaster moelleri also has flexuous setae on the mesosoma, but on moelleri all the setae on the mesosomal dorsum are long and flexuous, rather than just those on the humeri.
Description of worker
Color red brown to black; workers of relatively uniform size, lacking pronounced size polymorphism.
In face view head subquadrate, about as wide as long, with emarginate posterior margin; mandibles shiny, smooth or with faint striae; clypeus convex, smooth and shiny or more often with weak longitudinal rugulae that converge anteromedially; scapes just attaining posterior margin of head when laid back from insertions; terminal three segments of antenna gradually lengthening and broadening, becoming increasingly densely pubescent, terminal two segments very much larger, so that antennal club appears two-segmented; scapes with short appressed pubescence, sometimes subdecumbent, never erect, with no differentiated long erect setae; face with sparse appressed to subdecument pubescence and two short erect setae about midway between posterior border and posteriormost points of frontal carinae; malar spaces and space between eyes and antennal insertions with fine longitudinal striae, rest of face smooth and shining.
Promesonotal profile forming a single convexity, mesonotum slightly elevated posteriorly, dropping abruptly to propodeal suture; propodeal suture deep in dorsal view but not visible in lateral view due to lateral carinulae that bridge the suture, these carinulae with small denticle; dorsal and posterior faces of propodeum in same plane, sloping from propodeal suture to petiolar insertion, dorsal face a narrow anterior band with irregular rugulose sculpture, long posterior face smooth and shining; propodeal spines upturned, medium length, narrowly acute and spiniform; promesonotal dorsum with weak sculpture, usually with more or less longitudinally oriented rugulae or striae; side of pronotum smooth and shining, katepisternum weakly punctatorugose, often smooth and shining medially; side of propodeum largely smooth with faint longitudinal rugulae ventrally; pronotal humeri each with a long, relatively flexuous seta, two pairs of shorter, stiffer erect setae on mesonotum, occasionally a pair of short erect setae on dorsolateral propodeum; femora and tibiae with appressed to subdecumbent pubescence, no erect setae.
Petiole in lateral view subtriangular, sublucid, with faint microsculpture, ventral margin slightly concave, dorsal margin slightly convex; anteroventral petiolar tooth strongly developed, triangular, acute, curving ventrally; dorsal face of propodeum smooth and shiny, about as wide as long, sides convex, widest point of petiole about midlength; posterolateral tubercles each with a stiff erect posteriorly directed seta; postpetiole lacking ventral tooth, globular in dorsal view, about as long as wide, with about four erect posteriorly directed setae; fourth abdominal tergite smooth and shining, with sparse appressed pubescence and abundant long stiff flattened erect setae that are evenly distributed across tergite.
Measurements:
HL 0.580, 0.596, 0.848; HW 0.640, 0.643, 0.886; HC 0.619, 0.610, 0.881; SL 0.471, 0.481, 0.626; EL 0.137, 0.154, 0.208; A11L 0.218; A11W 0.123; A10L 0.105; A10W 0.091; A09L 0.056; A09W 0.067; A08L 0.044; A08W 0.057; WL 0.640, 0.631, 0.890; SPL 0.117, 0.104, 0.184; PTH 0.143, 0.126, 0.196; PTL 0.187, 0.166, 0.313; PTW 0.188, 0.193, 0.280; PPL 0.171, 0.180, 0.220; PPW 0.171, 0.168, 0.252; CI 110, 108, 104; OI 24, 26, 25; SI 81, 81, 74; PTHI 76, 76, 63; PTWI 101, 116, 89; PPI 100, 93, 115; SPI 18, 16, 21; ACI 1.05.
Description of Queen
A normal queen (dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum) with general shape, sculpture, and pilosity characters of the worker.
Natural History
Crematogaster erecta is a widespread species that occurs in a range of habitats including wet forest, seasonal dry forest, and thorn scrub. It seems to be more common in second growth or disturbed habitats than in mature forest. In Costa Rica it only occurs in the wet forests of the southern Pacific lowlands, on the Osa Peninsula and vicinity. Where it occurs it is abundant. Its nesting and foraging behavior is similar to C. crinosa and relatives, and it seems to be an ecological cognate to these.
Mature colonies are very large and may blanket the habitat, with no clear colony boundaries. These large polydomous colonies are sometimes clearly polygynous, with multiple dealate queens dispersed among nests, and other times large areas seem to have workers and brood only, or workers, brood and alate sexuals. In areas with large colonies, workers can dominate the vegetation during the day, with columns of workers streaming along vines, across shrubs, and up and down tree trunks. At Sirena guard station in Corcovado National Park, C. erecta is extremely abundant on the buildings themselves (where it is a house pest), on clothes lines, and in all the surrounding second growth vegetation. Workers form temporary bivouacs in almost any small plant cavity, and the colony takes the form of a vast network of columns connecting nodes of clustered workers in plant cavities. These nodes vary in size, from 2cm long dead twigs containing a dozen workers to large dead branchs with thousands of workers.
Colony founding seems to be claustral and single-queened, because I have multiple collections of lone foundresses from dead stems. Thus, polygyny in large colonies must be secondary, because pleometrotic foundress associations are not found.
Foraging is primarily diurnal. Foraging ceases at night, but workers will continue visiting a bait long into the night if it is discovered during the day and remains rewarding. At night the workers do not always return to a nest center. Instead they coalesce into the above mentioned nodes and scattered worker aggregations. Early in the morning dew-covered clusters of immobile workers occur throughout the habitat, slowly remobilizing as the sun rises and the environment warms up. Workers are omnivorous, recruiting to carbohydrate and protein baits, scavenging on dead or injured insects, and visiting extrafloral nectaries. They are aggressive around resources and will defend them from other insects. I once observed workers spend several hours cleaning a small lizard carcass, revealing that they will forage on carrion.
Synonyms
C. erecta Mayr 1866. Costa Rica to Amazonian Brazil, Peru.
= virgula Forel 1899. Costa Rica, Panama.
= projecta Santschi 1925. Surinam.
Figure 1. Workers of C. erecta attacking and "pestering" to death gregarious caterpillars of Heliconius hewitsoni in Corcovado National Park, Costa Rica. The Passiflora shoots upon which these larvae fed were sources of copious extrafloral nectar, and the ants seemed to be protecting their resource. The larvae were treated as intruders to be driven off rather than prey to be captured and returned to the nest.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Date of this version: 4 March 2003.
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