Stigmatomma oregonense

Stigmatomma oregonense
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Amblyoponinae
Tribe:	Amblyoponini
Genus:	Stigmatomma
Species:	S. oregonense
Binomial name
	Stigmatomma oregonense; Wheeler, W.M., 1915 Specimen Label

Stigmatomma oregonensis is found in shaded, mixed coniferous forest, where it nests in large rotten logs. Colonies are polygynous and often rather diffusely distributed throughout the log. The principal prey appears to be geophilomorph centipedes. Alates emerge in August and September.

At a Glance

• Larval Hemolymph Feeding

Photo Gallery

Stigmatomma oregonense transporting a larva. Quincy, California. Photo by Alex Wild.
Workers, larvae and pupae. The central worker is piercing the integument of a larva in preparation for larval hemolymph feeding. Quincy, California, USA. Photo by Alex Wild.
Larval hemolymph feeding by a worker (queen in background). Quincy, California, USA. Photo by Alex Wild.

Identification

Worker: inner border of mandible straight; anterior clypeal margin straight; large Stigmatomma species (HW 1.21-1.40), with broad head (CI 0.94-1.01).

S. oregonense has sometimes been misidentified as Stigmatomma pallipes (Ward 1988). The two species differ in the shape of the clypeus and mandibles (see the identification key). California S. pallipes are smaller and have narrower heads than S. oregonense, but some eastern S. pallipes overlap with S. oregonense in these dimensions (Ward 1988).

Keys including this Species

Distribution

Southern British Columbia through northern California; coastal in the northern part of its range, moving away from the coast into the Sierra Madre in California (Ward 1988).

Latitudinal Distribution Pattern

Latitudinal Range: 50.1° to 38.57892°.


North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

Source: AntMaps

Distribution based on Regional Taxon Lists

Nearctic Region: Canada, United States (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Ward (1988) - California records of S. oregonense come from regions of mixed coniferous forest, mostly in the rich transition zone of the Sierra Nevada, dominated by conifers of the genera Pseudotsuga, Pinus, Libocedrus and Abies, together with maple (Acer) and oak (Quercus). Elevation records (where given) range from 580 m to 1740 m. At two localities (in Plumas and Tuolumne Counties) I discovered populous, multiple-queen colonies of S. oregonense, with abundant brood, under the bark of large, moist, rotten coniferous logs, in shaded forest. Remains of a geophilomorph centipede were seen in one cluster of larvae.

Laboratory colonies of S. oregonense, maintained in small plaster-of-Paris nests and established from polygynous colony fragments collected in the field, also readily accepted geophilomorph centipedes. The centipedes were captured, stung, dragged into adjacent brood chambers, and, in some instances, cut into several pieces which were fed upon by larvae. Lithobiomorph centipedes did not elicit such a strong reaction and were not dragged over to the brood pile. Workers and queens were observed to assiduously lick the surface and exposed cuts of geophilomorphs. On one occasion three freshly laid eggs appeared on a geophilo morph, 24 hours after capture. Nevertheless, I was unable to sustain healthy brood production in these laboratory colonies of S. oregonense. All such colonies experienced considerable larval mortality and declined in size, although several adults (one queen, four workers) were kept alive on a diet of small arthropods (mostly Drosophila) for 16 months.

One of the laboratory colonies of S. oregonense was started from a field collection of workers and cocoons in late July 1984. Alate queens and males eclosed in this colony between August 6 and 14, 1984. Dates of field-collected S. oregonense alates from California and Oregon span the period August 22 to September 18. An alate queen from Forest Grove, Washington Co., Oregon bears the annotation "4 p.m., swarm before rain", suggesting that S. oregonense alates may fly earlier in the day than those of Stigmatomma pallipes. Alternatively, queens of both species might simply be released before males.

Wild (Notes From Underground, on-line, 23 May 2005) provides an engaging and lavishly illustrated account of a captive colony. Workers killed centipedes by repeated stinging, then carried the prey back to the nest for a prolonged period of mastication (one to several hours). During this time the workers consumed any droplets of hemolymph that oozed from the centipede. Larvae were then piled onto the centipede. Queens, and occasional workers, fed on larval hemolymph, puncturing the larvae to do so. Larvae developed scars at the puncture sites but otherwise seemed unharmed. This non-lethal cannibalism increased when the colony ran out of centipedes.

Castes

Worker

Images from AntWeb


Worker. Specimen code casent0005433. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by UCDC, Davis, CA, USA.


Type of Stigmatomma oregonense. Worker. Specimen code casent0103326. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by MCZ, Cambridge, MA, USA.


Type of Stigmatomma oregonense. Worker. Specimen code casent0172805. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by MCZ, Cambridge, MA, USA.

Queen

Images from AntWeb


Type of Stigmatomma oregonense. Queen (alate/dealate). Specimen code casent0172806. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by MCZ, Cambridge, MA, USA.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

oregonense. Stigmatomma pallipes subsp. oregonense Wheeler, W.M. 1915b: 389 (w.q.) U.S.A. (Oregon, Washington).
- Type-material: 13 syntype workers, 4 syntype queens.
- Type-localities: U.S.A.: Oregon, Marion (P.J. Schmitt), U.S.A.: Washington, Olympia (T. Kincaid).
- Type-depositories: AMNH, MCZC.
- [Stigmatomma pallipes subsp. oregonense Wheeler, W.M. 1910g: 561. Nomen nudum.]
- Combination in Amblyopone: Brown, 1960a: 169;
- combination in Stigmatomma: Yoshimura & Fisher, 2012a: 19.
- Subspecies of pallipes: Essig, 1926: 869; Creighton, 1940b: 7; Creighton, 1950a: 34; Smith, M.R. 1951a: 782.
- Status as species: Brown, 1960a: 169, 183, 192 (in key); Smith, M.R. 1967: 346; Smith, D.R. 1979: 1335; Wheeler, G.C. & Wheeler, J. 1986g: 17 (in key); Ward, 1988: 105; Lattke, 1991c: 6 (in key); Bolton, 1995b: 62; Lacau & Delabie, 2002: 40 (in key); Ward, 2005: 25.
- Distribution: Canada, U.S.A.

Taxonomic Notes

This species was described as a subspecies of Stigmatomma pallipes; it was raised to species by Brown (1960), who felt that the morphological differences between S. pallipes and S. oregonense were consistent enough to indicate that the two forms were probably separate species. Brown's intuition was validated by Ward (1988), who showed that the two forms occurred together in part of northern California.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Slightly larger than the typical pallipes; head somewhat shorter; antennal scapes longer, so that their reflected tips reach the lateral margin of the head two-thirds the distance from the anterior to the posterior corners; eyes distinctly larger; teeth on the anterior border of the clypeus smaller and more numerous (9 to 10). Petiole from above as broad as long, with convex sides. In the typical form it is distinctly longer than broad, with rather straight, subparallel sides. Sculpture, pilosity and color as in the type.

Queen

(dealated). Closely resembling the worker; eyes much larger than in the typical pallipes.

Type Material

Olympia Washington, Kincaid 1949. Museum of Comparative Zoology

References

Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 62, catalogue)

Branstetter, M.G., Danforth, B.N., Pitts, J.P., Faircloth, B.C., Ward, P.S., Buffington, M.L., Gates, M.W., Kula, R.R., Brady, S.G. 2017. Phylogenomic insights into the evolution of stinging wasps and the origins of ants and bees. Current Biology 27, 1019–1025 (doi:10.1016/j.cub.2017.03.027).
Brown, W. L., Jr. 1960a. Contributions toward a reclassification of the Formicidae. III. Tribe Amblyoponini (Hymenoptera). Bulletin of the Museum of Comparative Zoology 122: 143-230 (page 169, Combination in Amblyopone, and raised to species)

Ward, P. S. 1988. Mesic elements in the western Nearctic ant fauna: taxonomic and biological notes on Amblyopone, Proceratium, and Smithistruma (Hymenoptera: Formicidae). J. Kans. Entomol. Soc. 61: 102-124 (page 105, see also)

Wheeler, W. M. 1915b. Some additions to the North American ant-fauna. Bull. Am. Mus. Nat. Hist. 34: 389-421. (page 389, worker, queen described)

Yoshimura, M. & Fisher, B.L. 2012. A revision of male ants of the Malagasy Amblyoponinae (Hymenoptera: Formicidae) with resurrections of the genera Stigmatomma and Xymmer. PLoS ONE 7(3):e33325 (doi:10.1371/journal.pone.0033325).

References based on Global Ant Biodiversity Informatics

Creighton W. S. 1940. A revision of the forms of Stigmatomma pallipes. American Museum Novitates 1079: 1-8.
Mallis A. 1941. A list of the ants of California with notes on their habits and distribution. Bulletin of the Southern California Academy of Sciences 40: 61-100.
Parson G. L., G Cassis, A. R. Moldenke, J. D. Lattin, N. H. Anderson, J. C. Miller, P. Hammond, T. Schowalter. 1991. Invertebrates of the H.J. Andrews Experimental Forest, western Cascade Range, Oregon. V: An annotated list of insects and other arthropods. Gen. Tech. Rep. PNW-GTR-290. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 168 p.