Crematogaster navajoa

Crematogaster navajoa nests at the base of desert plants or under logs.

Identification
Buren (1968) - The workers of navajoa have a strong resemblance to Crematogaster clara, a species which has a much more hygrocolic habitat in the southeastern states and is partially arboreal. Since the known ranges are separated by approximately 700 to 800 miles or more, there should be no basis for confusion. The two species may be separated in the worker by the definitely, even though not strongly, entirely punctate thorax in navajoa. Other differences are that the erect hairs and the pubescent hairs are much longer in navajoa than in clara and that the base of the epinotum lacks vermiculate rugae in navajoa whereas these are nearly always present in clara.

There are only two other species in North America which at all resemble navajoa. These are Crematogaster pilosa and Crematogaster patei; the former is known only from the Eastern coastal plains in swampy areas, and the latter from the gulf coast of Mexico in an unknown habitat.

C. navajoa differs from pilosa by having the pubescence appressed on the gaster and legs, and by the punctate rather than striate or longitudinally rugose thorax, and from patei by its nearly entirely smooth and shining head and by having the pubescence on gaster and legs appressed.

The workers of this species have abundant, long (about 0.25 mm), erect hairs on the pronotum and mesonotum, with somewhat fewer hairs on the dorsum of the propodeum and the propodeal spines. The side of the pronotum is finely sculptured with striae or poorly defined punctures, but mostly smooth and shiny. The side of the mesosoma and propodeum are covered with striae intermixed with punctures. (Mackay and Mackay 2002)

Key to western US Crematogaster

Distribution
Arizona and New Mexico.

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

Field Observations
Chris Yazzie - The habitat is pinyon trees, juniper trees, sage brush, cacti, small grass. The soil is very rocky. Found workers foraging under a pine tree, its nest went into the base of the trunk into the earth. The ants had a trail leading a foot away into another nest that was buried by fallen pine needles. Another trail went a couple of feet to a young pine tree that was about 3 feet high, in the upper branches of the pine, ants were tending aphids in multiple places under the tree limbs and branches. Colony had multiple queens. Reproductives present in the nest in late June.

Nomenclature

 *  navajoa. Crematogaster (Crematogaster) navajoa Buren, 1968b: 102 (w.q.) U.S.A.

Worker
Length, about 3.5 to 4.0 mm., an occasional specimen up to 4.5 mm.

Head slightly broader than long in most specimens, in largest workers distinctly broader than long; sides of head convex, rear border usually slightly concave. Cypeal border gently convex. Scapes rather variable in comparative length, this not always exactly correlated with head size, usually surpassing the hind corners by about two diameters, in largest workers scarcely surpassing the hind corners. Pronotal humeri only moderately developed throughout the size range, no oblique lateral pro-mesonotal impressions. Mesonotal median carina high and sharp on the front half or front two-thirds of the mesonotum. The height of this structure is especially noticeable in profile. Mesonotal declivity gently sloping in large workers, in small workers scarcely noticeable. Spines rather short, slender, and sharp, only weakly divergent, and often slightly convex on the outer sides seen from above, thus somewhat similar to the appearance in browni. Petiole of the usual trapezoidal shape, but this less strong than in most species, the anterior corners not strongly produced and the anterior borders, seen from above, sweeping obliquely caudad from the pedicel rather than being carried at right angles laterad. Postpetiole, however, very broad and well developed, very nearly as, or sometimes even slightly wider than the petiole; the hemilobes very well developed and globose, very convex laterally, and separated by a deep median sulcus; in profile they are moderately produced posteriorly.

Head mostly smooth and shining, with some shagreening on vertex and occiput. Mandibles and genae with usual strong striae, middle of clypeus usually without them. Thorax entirely but very shallowly punctate, subopaque. There are some weak irregular rugae often on the front of the pronotum and the humeri, and some weak irregular striae often on base of epinotum. Sides of pronotum punctate. Lower mesopleura punctate and also often with some weak striae.

Head with very few long erect hairs on dorsal surfaces, but beset with long erect pubescence on all surfaces including the scapes. Thorax with a band of very long, flexuous, erect hairs across the front of the pronotum, and several more pairs of long, erect hairs on dorsum and rear of mesonotum. Petiole and postpetiole with the usual posterior hair pairs long and flexuous and with some accessory hair pairs. Gaster with scattered long erect hairs. Pubescence on thorax and legs erect or suberect. Pubescence on dorsum of gaster long but entirely appressed.

Head, thorax, petiole, postpetiole, and appendages dark brown. Gaster black.

Queen
Large robust females 9-10 mm. in length with large heavy gasters often 5 mm. long and 3 mm. wide.

Head a little broader than long, with weakly convex sides and rear border. Scapes usually not quite reaching hind corners in full face view. Frontal furrow weak and scarcely noticeable. Neither eyes nor ocelli large or prominent. Mesoscutum as wide as long. Scutellum much wider than long. Spines short but sharp, a little longer than diameters of their bases. Metanotum often produced medially into a blunt process. Petiole as in the worker, without strong anterior corners. Postpetiole unlike that of the worker, trapezoidal, with nearly straight sides and wider in front than behind as in the females of many species.

Head entirely smooth and shining except for a large number of piligerous punctures and the usual coarse striae on mandibles, genae, and sides of front. Those on the genae carried slightly past the eyes. Median part of clypeus without striae. In lateral view, front half of pronotum strongly shagreened and roughened, posterior half smooth and shining. Mesopleura nearly entirely smooth and shining except for large piligerous punctures. Rear half of sides of mesosterum striato-punctate. Metapleura strongly striate. Base of epinotum irregularly striate or rugose. Sides of mesoscutum with some elongate piligerous foveolae as in Crematogaster browni, rest of dorsum of thorax with numerous piligerous punctures.

Head with moderately numerous, long, erect hairs on front but also beset with abundant long, flexuous pubescent hairs on all surfaces, including the scapes. These are especially noticeable in full face view on the genae in front of the eyes and on the rear border and corners of the head. Thoracic dorsal surfaces covered with very numerous erect hairs. The pubescent hairs are suberect on the thorax but are much shorter and less conspicuous than on the head. Dorsum of gaster with rather numerous erect hairs and moderately long suberect pubescent hairs. Legs with suberect to erect pubescence, long and flexuous only on the coxae and flexor surfaces. Concolorously very dark brown to black. Radius vein to the stigma dark brown. Stigma and remaining veins light brown to colorless.

Type Material
The type locality of this new species is 8 mi. E. of Seligman, Ariz., where I took numerous specimens under rocks on Aug. 11, 1957, and Aug. 16, 1958, in juniper-grassland. I have also captured this species near Rainbow Lodge in the Petrified Forest National Monument, Ariz. and the Painted Desert, Ariz., all specimens in these two localities captured at the bases and roots of sagebrush and other desert plants. No specimens could be found under the pieces of petrified wood or other rocks in these localties. I have chosen a worker from the Seligman locality to be the holotype and all the other specimens have been labeled as paratypes. Holotype and worker and female paratypes are to be deposited in the National Museum, and paratypes are to be deposited in the California Academy of Sciences, the Museum of Comparative Zoology and the American Museum of Natural History. I will retain a fairly large number of paratypes.

Etymology
All the records taken so far are from the Colorado Plateau in northern Ariz. and northwestern New Mexico, which corresponds roughly with the original home range of the Navajo Indian Nation, hence the name.