Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Image catalog (click here).
Range
USA (Florida), Mexico, Guatemala, Belize, Costa Rica, Venezuela.
Identification
The combination of punctate face, appressed tibial pilosity, and normal propodeal spines (as opposed to spines that are reduced to denticles or tubercles) uniquely identify this species in Costa Rica.
Description of worker
Color red brown, gaster and face darker than rest of body.
Mandibles shiny, longitudinally striate, striae faint to pronounced; face with conspicuous microaerolate sculpture over most of surface, with a smooth shiny strip medially, extent of medial strip variable; scapes with abundant long subdecumbent to suberect pubescence, lacking differentiated long, erect setae; antennal club 2-segmented; clypeus shiny with 2-4 longitudinal rugulae; face with dense stubble of 30-40 short, stiff, erect setae; ventral surface of head smooth and shiny with sparse suberect to subdecumbent pilosity.
In lateral view, dorsal profile of pronotum, mesonotum, and propodeum forms continuous curve, dorsal and posterior faces of propodeum in same plane, sloping to petiolar insertion; propodeal spines projecting posterodorsally; pronotal dorsum with clathrate sculpture forming a lattice of longitudinal and transverse carinae with smooth and shiny interspaces; mesonotal dorsum with low, longitudinal carinulae laterally, microareolate sculpture medially; propodeal suture impressed medially but not visible in side view because lateral mesonotal carinulae continue onto dorsal face of propodeum; mesonotal carinulae have slight tooth at propodeal suture; dorsal face of propodeum very short, only visible in dorsal view, differentiated from posterior face by transverse carina, dorsal and posterior faces with faint microaerolate sculpture; propodeal spines short, thin, and sharp; side of mesosoma mostly microareolate/punctate, with variable degree of weakening of sculpture on side of pronotum, becoming entirely smooth and shining in some cases; setae on mesosomal dorsum stiff, relatively short, of variable length, longest approximately 0.14mm long, dorsum of pronotum with anterior row of four setae, anterolateral and posterolateral dorsum of mesonotum (at propodeal suture) each with a seta; propodeal spine with one long seta at base, subequal in length to spine; additional shorter setae dispersed among primary setae; legs with appressed to subdecumbent pubescence and no erect setae.
Petiole in side view trapezoidal; side densely microareolate/punctate; with acute anteroventral tooth; dorsal face subquadrate, about as wide as long, faintly microareolate or smooth and shining; posterodorsal face short, densely microareolate; posterolateral tubercles each with two stiff setae; postpetiole in dorsal view subrectangular, wider than long, with slight posterior emargination; postpetiole with small anteroventral tooth; dorsum and sides with microareolate sculpture; with 4-6 stiff erect setae; fourth abdominal tergite with very faint, areolate microsculpture, shiny, with about 50 stiff erect setae evenly dispersed over surface.
Measurements:
HL 0.593, 0.555, 0.622; HW 0.633, 0.608, 0.657; HC 0.584, 0.542, 0.611; SL 0.539, 0.511, 0.546; EL 0.161, 0.145, 0.162; A11L 0.242; A11W 0.119; A10L 0.116; A10W 0.109; A09L 0.061; A09W 0.065; A08L 0.041; A08W 0.067; WL 0.646, 0.580, 0.671; SPL 0.137, 0.116, 0.130; PTH 0.161, 0.150, 0.162; PTL 0.173, 0.163, 0.191; PTW 0.196, 0.166, 0.186; PPL 0.149, 0.124, 0.135; PPW 0.210, 0.173, 0.196; CI 107, 110, 106; OI 27, 26, 26; SI 91, 92, 88; PTHI 93, 92, 85; PTWI 113, 102, 97; PPI 141, 140, 145; SPI 21, 20, 19; ACI 1.75.
Queen
I have not observed the syntype queen of Wheeler's agnita, and I have seen no other queens of obscurata. Given the similarity of obscurata to steinheili, I assume it has queens like those of steinheili, which are normal queens (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 obscurata occurs in dry forest habitats and beach margins. Mark Deyrup recently discovered a nest in the Florida keys, where it is most likely a recent introduction. I have collected the species twice in Costa Rica, both collections from Santa Rosa National Park in the seasonally dry habitats of Guanacaste Province. One collection was made while collecting at night in second growth dry forest near the park administrative headquarters. An aggregation of workers was in a tree knot. The second collection was from Playa Naranjo, at the upper beach edge. Small necrotic spots in live stems of a small Gliricidia sepium tree (Fabaceae) contained aggregations of workers only, with no brood or sexuals. The collection was made in the late afternoon, and the workers were not foraging. Even when the cavities were disturbed, the workers remained quiescent, appressed to the walls. The types of Wheeler's agnita were collected in hollow twigs, and workers have been twice intercepted in U.S. quarantine stations, in both cases in Oncidium orchids from Guatemala.
Comments
Crematogaster obscurata is part of a complex of species that occurs throughout the Neotropics. It is essentially a darker version of C. steinheili Forel, a yellow species that occurs on many Caribbean islands. In South America, versions of this complex include victima F. Smith 1858 and victima cisplatinalis Mayr 1877. These South American forms differ only in small details of color, sculpture, and pilosity. One character the South American forms exhibit is that the pronotal dorsum is densely punctate beneath the clathrate sculpture, rather than shiny or weakly microareolate. The entire lineage favors xeric regions.
Synonyms
C. obscurata Emery 1895. USA (Florida), Mexico to Venezuela.
= agnita Wheeler 1934. Guatemala.
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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