Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Image catalog, worker and queen, montage images (click here).
Images of lectotype (click here).
Range
Costa Rica, Colombia, Brazil (Espirito Santo, Rio de Janeiro).
Identification
Crematogaster evallans and the similar species C. acuta share a unique combination of characters: largely punctate face, erect tibial pilosity, and abundant clear to whitish (not amber, as in arcuata) long erect setae on the face and mesosomal dorsum. The two species may be distinguished by several characters, but perhaps the most discrete is the acute ventral postpetiolar tooth on acuta, contrasted with a bluntly rounded lobe on evallans.
Description of worker
Color dark red brown to black.
Head subquadrate, posterior margin emarginate, with compound eyes projecting beyond lateral margins in full face view; mandibles striate; clypeus emarginate anteriorly, convex, with faint microareolate surface sculpture and widely spaced weak rugulae that converge anteromedially; face punctate over much of surface, with variably developed anteromedian strip on face smooth and shiny; scape surface etched, subopaque; scape with abundant erect setae, setae as long as width of scape or greater; antennal club not well defined, terminal 3-5 segments gradually lengthening and becoming increasingly densely pubescent, often appearing distinctly 3-segmented; face with abundant long erect fine whitish setae, both on dorsal surface and projecting from sides; malar spaces and ventral surface of head with abundant short erect to suberect setae.
In lateral view, dorsal profile of promesonotum moderately convex, mesonotum differentiated from pronotum, projecting and forming elevated anterior boss; propodeal suture a deep crease medially, visible in dorsal view, but thin lateral carinulae bridge suture, such that in lateral view suture appears broad, shallowly impressed; dorsal and posterior faces of propodeum not well differentiated, together in nearly the same plane as mesonotal dorsum; propodeal spines thin, long, sharp; side of pronotum evenly punctate and medially impressed; anepisternum and katepisternum evenly punctate; side of propodeum faintly microareolate to smooth and shining, always with much weaker sculpture than side of pronotum and katepisternum; promesonotal dorsum uniformly punctate, sometimes overlaying faint traces of clathrate rugae; dorsal and posterior faces of propodeum faintly microareolate, often fading to smooth and shiny posteriorly; promesonotum and dorsal face of propodeum with abundant long whitish setae; legs with combination of abundant suberect and decumbent setae.
Petiole in side view subtriangular, uniformly punctate; anteroventral tooth a shallow, obtuse gibbosity, not produced or angulate; dorsal face rectangular, about twice as long as wide, smooth and shiny on anterior two thirds, grading to faintly microaerolate posteriorly; postpetiole with short, blunt ventral tooth, postpetiole in dorsal view subquadrate, wider than long, with longitudinal median sulcus, posterior margin emarginate; anterolateral margin nearly perpendicular to stem of helcium, node of postpetiole separated from helcium by a distinct sulcus; fourth abdominal tergite with faint microareolate sculpture; abundant erect long whitish setae on posterodorsal petiole, postpetiole, and fourth abdominal tergite.
Measurements:
HL 0.686, 0.634, 0.667; HW 0.742, 0.686, 0.693; HC 0.688, 0.631, 0.662; SL 0.664, 0.624, 0.655; EL 0.170, 0.152, 0.152; A11L 0.279; A11W 0.116; A10L 0.133; A10W 0.101; A09L 0.090; A09W 0.075; A08L 0.058; A08W 0.063; WL 0.791, 0.731, 0.758; SPL 0.202, 0.185, 0.188; PTH 0.193, 0.178, 0.182; PTL 0.277, 0.231, 0.241; PTW 0.213, 0.199, 0.195; PPL 0.198, 0.185, 0.189; PPW 0.292, 0.251, 0.254; CI 108, 108, 104; OI 25, 24, 23; SI 97, 98, 98; PTHI 70, 77, 76; PTWI 77, 86, 81; PPI 147, 136, 134; SPI 26, 25, 25; ACI 0.14.
Description of Queen
In lateral profile dorsal face of propodeum sloping obliquely from postscutellum, such that most of propodeum is posterior to scutellum (in contrast to normal queens, in which dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum); entire body, including scape, mandible, face, mesosoma, petiole, postpetiole, and fourth abdominal tergite smooth and shiny; propodeal spines long, acute; petiole and postpetiole robust, generally similar to worker in shape but completely lacking anteroventral petiolar tooth of any kind, and petiole relatively shorter, dorsal face only slightly longer than broad; appendages, dorsal surfaces of head, mesosoma, and postpetiole, and posterodorsal surface of petiole with abundant erect whitish setae; queens from Colombia, Dept. Magdalena relatively less pilose, with setae very sparse on fourth abdominal tergite; queens from Dept. Huila much more pilose, almost lanose over entire body, including fourth abdominal tergite; also, queens from Dept. Magdalena have relatively larger heads then queens from Dept. Huila.
Natural History
Crematogaster evallans is found in wet forest habitats. Like other relatives of C. acuta, it appears to have large colonies that are at low density and infrequently encountered. In Costa Rica I have observed it several times in Corcovado and Manuel Antonio national parks, usually as a rapid column of workers descending a tree and fanning out onto the ground or low vegetation. In one case I saw worn trails in the moss on a tree trunk, suggesting a large colony with regularly used trunk trails. I have seen only one nest, which was at a site near Santa Marta in Colombia, along a road edge. Multiple dead branches were lodged in a vine tangle about 4m high in a small tree. A large colony occupied all the dead branches. The branches had been hollowed out by termites, and abandoned termite carton filled the interiors. Workers and alate queens were thinly scattered throughout the branches. There were few large aggregations of workers, and few of the nests contained any brood. There was no obvious colony center, and it is likely that these branches contained only part of a much larger colony that occurred higher in the tree. The nests contained numerous inquiline beetles and at least one silverfish (Atelurinae).
Nothing is known of colony founding, but queens exhibit a morphology often associated with social parasitism.
Synonyms
C. evallans Forel 1907. Costa Rica, Colombia, Brazil (Espirito Santo, Rio de Janeiro).
= carbonescens Forel 1913. Brazil (Espirito Santo).
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Date of this version: 19 June 2003.
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