Dorymyrmex grandulus

A small Dorymyrmex species that occurs in woodland and adjacent open areas.

Identification
Trager (1988) - A small dusky yellowish brown to dark brown species. Forel (1922) described specimens of this this species as a variety of Nylanderia parvula.

Superficially, D. grandulus resembles a depauperate Dorymyrmex medeis (=Dorymyrmex smithi), but has proportionately smaller and narrower head with occipital border weakly convex and propodeal cone sharp with narrow base.

Distribution
Trager (1988) - Known from Alabama, northern Florida, and the eastern seaboard states north at least to the New Jersey Pine Barrens. The true range of this ant may be much more extensive. I have seen similar Dorymyrmex specimens collected in Michigan and New York, but have not had the opportunity to study them carefully. Buren (personal communication) felt that Michigan specimens he saw were "probably different", but sensing his caution, I prefer to leave open the question of their conspecificity with D. grandulus.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.

Biology
Trager (1988) - Until I serendipitously discovered the types of D. grandulus, Buren had intended to describe this species as new with a name referring to its frequent occurrence in woodland openings. Specimens from Georgia are labeled "pine-oak on clay"; however most series have been collected in sandy soils. One series was from sand dunes, and the level of development of the vegetation was not indicated, and I made one collection of this species at the edge of a temporary pond in full sun, many meters from the nearest tree. The types were collected by Forel without a habitat notation, but he also collected Nylanderia faisonensis at the type locality; the latter is a species of mesic woodlands.

Nomenclature

 *  grandulus. Prenolepis (Nylanderia) parvula var. grandula Forel, 1922: 98 (w.) U.S.A. Trager, 1988: 24 (q.). Combination in Paratrechina (Nylanderia): Emery, 1925b: 222; Creighton, 1950a: 409; in Conomyrma: Trager, 1984b: 64; in Dorymyrmex: Shattuck, 1992c: 85. Junior synonym of parvula: Creighton, 1950a: 409. Revived from synonymy and raised to species: Trager, 1984: 64. See also: Johnson, C. 1989b: 192 (in key).

Trager (1988):

Worker
HL 0.63-0.90 (0.82), HW 0.53-0.75 (0.67), SL 0.63-0.91 (0.85), EL 0.16-0.23 (0.22), FL 0.55-0.80 (n.a.), WL 0.83-1.18 (1.13), HTL 1.46-2.08 (1.95), CI 80.0-87.3 (82.0), SI 110.3-130.0 (126.9), OI 22.7-28.6 (26.8), FI 80.8-93.6 (n.a.), TI 124.0-140.0 (138.0). N =21. Lectotype selected and measured by Roy R. Snelling, LACM; deposited in Forel collection Museum d'Histoire Naturelle, Geneva, Switzerland.)

General form and characters as in figures, and in key.

Head shape variable, ranging from that shown in figures to more nearly straight-sided and convergent toward occipital border (this variation may be found in any large nest series of D. grandulus and has no relationship to overall body size); head usually widest across eyes; promesonotal profile often as in figure, but often contiguous faces of pro- and mesonota higher and more arched; rarely mesonotal profile strongly arched, obliterating usual angle (one will not be able to take such specimens through key but other specimens from same series will have the normal conformation); propodeal profile reminiscent of that of Dorymyrmex medeis (=Dorymyrmex smithi), but basal face of propodeum 2 or more times as long as base of propodeal cone (only I to 2 times as long in C. medeis) and cone is generally sharper-tipped than in D. medeis; propodeal cone often appears inclined forward.

Mandibular striation similar to that of Dorymyrmex bureni in extent, but consisting of 3 or 4 coarser striae with 1-2 finer striae adjacent to each of these; tessellation coarser than in D. bureni, thus cuticle shinier, but this obscured by longer pubescence.

Color of D. grandulus varying from piceous to yellowish brown; often clypeus and thorax a little yellower, and occasionally (teneral?) both head and thorax yellowish; mandibles yellow to brown; legs about the color of gaster; D. grandulus usually has a "mousy" color due to the obscuring of the cuticle by longer than average (for the genus), grayish pubescence.

Queen
HL 1.20-1.25, HW 1.23-1.28, SL 1.09-1.15, EL 0.40-0.43, TW 1.18-1.30, WL 2.38-2.45, HTL 3.58-3.70, CI 95.4-103.7, SI 84.4-93.2, OI 32.0-34.4, TWI 93.8-107.8, TI 194.4-204.2. N =6

Head a little broader than long: sides weakly convex or faintly angular, converging slightly toward occipital border, more strongly so toward clypeus; outer margin of eyes close to or reaching sides of head; occipital border about as broad as clypeus; thorax usually notably broader than head.

Sculpture coarser and pubescence longer than in worker, thus queen notably duller; color uniform dark brown or with head and thorax a little lighter and more reddish.

Type Material
Lectotype and 1 paratype: North Carolina, Duplin Co.: Faison, A. Forel, 1921.

Etymology
The adjective grandulus is the diminutive form of Latin grandis (large). Dr. Forel (1922) noted that this species was somewhat larger than the species with which he mistakenly believed D. grandulus to be conspecific, Nylanderia parvula.

References based on Global Ant Biodiversity Informatics

 * Annotated Ant Species List Ordway-Swisher Biological Station. Downloaded at http://ordway-swisher.ufl.edu/species/os-hymenoptera.htm on 5th Oct 2010.
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 * MacGown J. A., and R. Whitehouse. 2015. A preliminary report of the ants of West Ship Island. A report submitted to the Gulf Islands National Seashore. Mississippi Entomological Museum Report #2015-02. 9 pp.
 * MacGown, J.A and J.A. Forster. 2005. A preliminary list of the ants (Hymenoptera: Formicidae) of Alabama, U.S.A. Entomological News 116(2):61-74
 * MacGown, J.A. and T. Lockley. Ants of Horn Island, Jackson County, Mississippi
 * Shattuck S. O. 1994. Taxonomic catalog of the ant subfamilies Aneuretinae and Dolichoderinae (Hymenoptera: Formicidae). University of California Publications in Entomology 112: i-xix, 1-241.
 * Trager J. C. 1988. A revision of Conomyrma (Hymenoptera: Formicidae) from the southeastern United States, especially Florida, with keys to the species. Florida Entomologist 71: 11-29
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