Crematogaster snellingi Longino 2003

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker lateral view

worker face view

Image catalog (click here). Includes images of holotype.

Range

Costa Rica.

Identification

The combination of (1) shiny face with erect setae, (2) subquadrate dorsal face of petiole, (3) erect tibial pilosity, (4) dark coloration at least on head and abdomen, (5) relatively long upturned propodeal spines, and (6) acute to right-angle anteroventral propodeal tooth uniquely characterize this species. It can be confused with limata and relatives but differs in the more subquadrate, less tapering dorsal face of petiole and the relatively upturned spines. In some ways it is like a small, darkly colored sumichrasti.

Description of worker

Color varies from dark red brown to variously bicolored (see Variation); workers monomorphic in size.

Mandibles striate; clypeus with two longitudinal carinulae at anterior margin, anterior margin gently convex; head longer than wide, with posterior margin rounded laterally, weakly impressed medially; antenna with terminal two segments enlarged to form a club, third segment from end somewhat enlarged, blurring distinction between two and three-segmented club; scapes with abundant long erect setae of variable length, some longer than maximum scape width; when scapes laid back from antennal insertions, they barely surpass margin of vertex; face smooth and shining; face covered with an even covering of shorter curved setae and longer straight setae, setae flexuous to somewhat stiffened, light to dark amber (see Variation), no appressed pubescence; in face view abundant setae project from lateral and posterior margins.

Pronotum in lateral profile convex, rounding into flat dorsal face of mesonotum, posterior face of mesonotum short, dropping to propodeal suture; propodeal suture deep in dorsal view but partially obscured in profile due to lateral carinulae that bridge the suture; propodeum with or without differentiated dorsal face (see Variation); propodeal spines long, spiniform, upturned; pronotal dorsum smooth and shining or in robust specimens with traces of longitudinal carinulae; dorsal face of mesonotum with strong lateral carinae, terminating posteriorly at angular juncture with carinulae extending down posterior face and across propodeal suture; medial mesonotum concave, smooth and shining; dorsal face of propodeum, when differentiated, with longitudinal carinulae; posterior face flat to concave, smooth and shining; side of pronotum smooth and shining; katepisternum and side of propodeum shining, largely smooth with traces of feeble carinulae around margins of katepisternum; a pair of long setae on pronotal humeri (0.28mm), pairs of setae on anterolateral mesonotum, posterolateral mesonotum, and dorsolateral propodeum midlength between spines and propodeal suture, these three pairs subequal in length (0.15mm), anteromedian pronotum with a pair of setae that are variably developed, often shorter than mesonotal setae and slanted posteriorly, shorter setae variably dispersed on mesosomal dorsum, including on propodeal spines; mesosomal setae light to dark amber, flexuous; tibiae with abundant erect to subdecumbent setae, of variable length, some tibial setae subequal to maximum width of tibia.

Petiole in side view trapezoidal, smooth and shining, with rounded anteroventral tooth; dorsal face of petiole smooth and shining, longer than wide, varying in shape, with sides that gradually taper toward petiolar insertion or sides that are subparallel to level of petiolar spiracles then more abruptly tapering to insertion; posterolateral tubercles with 2-3 amber setae; postpetiole anteroventrally angulate or in robust specimens somewhat developed as subacute tooth; postpetiole in dorsal view globular, longer than wide, somewhat teardrop shaped, with 6-8 amber setae; fourth abdominal tergite smooth and shining, with abundant long flexuous to somewhat stiffened suberect amber setae, no appressed pubescence.

Variation:

Workers from the Peľas Blancas Valley on the Atlantic slope are dark red brown, gradually becoming lighter yellow on tarsi and antennal club. Workers from elsewhere on the Atlantic slope and from Carara on the Pacific slope tend to have the mesosoma, petiole, postpetiole, and legs lighter red brown, with head and gaster darker brown. Workers from sea level on the Osa Peninsula have the mesosoma, petiole, and postpetiole light red-brown, head slightly darker, gaster much darker, and the legs and tips of antennae almost yellow. The yellow coxae sharply contrast with the red brown mesosoma.

Workers from montane habitats are generally more robust. In some cases the mesonotum is somewhat raised anteriorly, meeting pronotum at an angle. The anteroventral postpetiolar tooth is more developed. The dorsal face of the propodeum is more differentiated and sculptured with longitudinal carinulae. The dorsal setae of head, mesosoma, and fourth abdominal tergite are dark amber. Workers become less robust and lighter colored at low elevations, reaching an extreme in workers from coastal forests of the Osa Peninsula. Workers from the Osa and from the Peľas Blancas Valley are quite distinct, but seem to be connected by a series of intermediates.

Measurements:

Holotype: HL 0.507, HW 0.542, HC 0.489, SL 0.448, EL 0.137, WL 0.598, SPL 0.116, PTH 0.135, PTL 0.180, PTW 0.137, PPL 0.147, PPW 0.146, CI 107, OI 27, SI 88, PTHI 75, PTWI 76, PPI 99, SPI 19.

Other specimens: HL 0.507, 0.602, 0.639; HW 0.545, 0.636, 0.650; HC 0.496, 0.582, 0.592; SL 0.448, 0.535, 0.576; EL 0.141, 0.149, 0.154; A11L 0.218; A11W 0.101; A10L 0.111; A10W 0.095; A09L 0.052; A09W 0.061; A08L 0.043; A08W 0.055; WL 0.591, 0.698, 0.722; SPL 0.113, 0.158, 0.161; PTH 0.150, 0.182, 0.175; PTL 0.201, 0.228, 0.221; PTW 0.151, 0.178, 0.190; PPL 0.137, 0.146, 0.168; PPW 0.160, 0.194, 0.191; CI 107, 106, 102; OI 28, 25, 24; SI 88, 89, 90; PTHI 75, 80, 79; PTWI 75, 78, 86; PPI 117, 133, 114; SPI 19, 23, 22; ACI 1.98.

Natural History

Crematogaster snellingi occurs in lowland and mid-montane wet forest habitats on both sides of Costa Rica. It is an infrequently collected species and I have never found a nest. Most collections are scattered foragers found on low vegetation at night. I have encountered diurnal foragers only when they are visiting extrafloral nectaries. In Corcovado, I once attracted a few workers to baits of mixed honey and vegetable shortening placed out on the ground at night. I also have obtained workers in Winkler samples of sifted leaf litter from the forest floor.


Literature Cited

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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