Dorymyrmex flavus

In an Oklahoma study Roeder et al. (2018) found the CTmax (critical thermal maximum) for this species was 51.5 ± 0.5 C and the average worker mass was 0.216 ± 0.012 mg.

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

Biology
Snelling (1195) - This species has been recently collected in a park near Blythe, Riverside County, California. Since D. flavus appears to be absent over most of New Mexico and all of Arizona, it seems likely that this California record represents an accidental introduction. The county park near Blythe is on the banks of the Colorado River and is heavily used by travellers from other states. The ant is now abundant in that park but has not been collected elsewhere in California.

Nomenclature

 *  flavus. Dorymyrmex flavus McCook, 1879: 188, figs. a-c (w.) U.S.A. Johnson, C. 1989b: 190 (q.m.); Cokendolpher & Francke, 1985: 349 (k.). Combination in Conomyrma: Kempf, 1972a: 80; in Dorymyrmex: Shattuck, 1992c: 85. Subspecies of pyramicus: Mayr, 1886d: 433; Forel, 1911e: 285. Junior synonym of pyramicus: Creighton, 1950a: 348; of insanus: Snelling, R.R. 1973b: 5. Revived from synonymy, revived status as species and senior synonym of nigra: Johnson, C. 1989b: 187. See also: Snelling, R.R. 1995: 5.
 * nigra. Dorymyrmex pyramicus var. nigra Pergande, 1896: 871 (w.) MEXICO. Forel, 1912h: 36 (q.). Combination in Conomyrma: Kempf, 1972a: 79. Junior synonym of pyramicus: Creighton, 1950a: 348; of insanus: Snelling, R.R. 1973b: 5; of flavus: Johnson, C. 1989b: 187.

Type Material
Snelling (1995) - In selecting a lectotype specimen, Johnson had available to him a few specimens from Larissa, Cherokee County, Texas, a community that no longer exists. These specimens were labelled as "Dorymyrmex insanus var. flavus McC." in McCook's handwriting. Johnson assumed, perhaps correctly, that these were some of the original material examined by McCook. However, this is not absolutely certain, and it is entirely possible that these were specimens collected and identified at a later date. The note that the ants were "destroying cotton worms" would seem to suggest that they may, indeed, be original material. While McCook cited the distribution to be "Southern States," he did not specifically mention anyone state. Nor is there any reason to assume that McCook ever understood that there are other yellow species of Dorymyrmex in the southern states. Rather, it seems likely that with material from several states (implied by his statement on the distribution of D. flavus), McCook almost certainly had a mixed series.

As in the case of the neotype designation for D. insanus, Johnson did not use original orthography when designating his "lectotype": the specimen is labelled "Conomyrma flava (McCook)," rather than Dorymyrmex insanus var. flavus. I have examined with great care the few Larissa specimens that comprise the putative type series. There are a total of six specimens mounted on a single card on which were cut eight points; two specimens obviously now are lost, as indicated by the glue remnants on the two empty points.

The condition of these specimens is discouraging. When originally mounted, all were crushed against their respective points; gasters were uniformly flattened. Legs were "scrunched" up against and over the body, and the specimens are more or less covered by the adhesive material. In most specimens the heads are crushed and distorted. Finally, the specimens are dirty, with panicles of sand and other attached debris; the mouthparts cannot be studied because they are occluded by sand panicles and, in most specimens, glue as well. It is possible, however, to determine that the integument of the head and mesosoma is distinctly tessellate and moderately shiny.

These difficulties are true of all the Larissa specimens except the putative lectotype. In that specimen the head and body are not crushed; the gastral distonion is minor and limited to that resulting from normal drying of internal tissues. The specimen is not crushed flat against the point. The legs and antennae are fully visible, and no significant portions of the body are obscured by adhesive, din, or other debris; there is not a sand panicle to be seen anywhere on this specimen, including the mouthparts.

The "lectotype" differs radically from the other specimens on the card in one crucial character: in all the other individuals the mesonotal profile is obtusely angulate. Originally this feature was concealed, but I moved or removed legs so that the mesonotum was visible in all specimens. In the "lectotype" the mesonotum is nearly straight, exactly as in D. bureni.

Johnson's "lectotype" differs from the remaining specimens on the card in other features as well. The integument of the head and mesosoma is less sharply tessellate, hence shinier. Although difficult to determine in the other five specimens, the head of the "lectotype" is apparently both longer and relatively narrower; the antennal scape is proportionately longer. The psammophore is slightly nearer the oral cavity than the occipital foramen in the "lectotype" but slightly nearer the foramen in the others.

In short, in terms of preparation technique, physical condition, and morphological characteristics, the putative "lectotype" differs sharply from the other specimens with which it is now associated. In my opinion, it is conspecific with D. bureni and not with the other specimens on the card, all of which can be safely referred to D. flavus as that name has usually been interpreted. I can only conclude that Johnson's "lectotype" is, in fact, a specimen of D. bureni added to the card at a date later than the other specimens. As such, it is invalid and must be set aside.

At the same time, I do not believe it advisable to select a true lectotype from among the five authentic Larissa specimens, none of which is in sufficiently good condition that the important morphological characteristics are readily visible. Furthermore, while it is possible, even likely, that McCook had these specimens available when he described this ant, there is no way to prove that this is so.

The only obvious solution is to set aside all the Larissa specimens and to assume that no provable type material exists. It is then possible to designate a neotype that is consistent with McCook's original description and conforms to the visible morphological characteristics of the Larissa specimens. I have, therefore, selected as neotype a worker specimen collected 21 mi W Monahans, Ward Co., Texas, 6 June 1979, by O.F. Francke,].V. Moody, and F. W. Merickel; neotype is deposited in ; neoparatypes (8 females, 91 workers, 3 males) in, , , and USNM.

Worker
Snelling (1995) - Neotype, measurements (mm): HL 0.87; HW 0.74; SL 0.85; EL 0.27; TL 2.94. Indices and ratios: CI 85; SI 97; SI 2 114; 01 31; OMR 140; IOR 130.

Head broadest at level of eyes; in frontal view, sides gently and evenly convex, above broadly rounded onto venex; venex slightly convex in frontal view. Eye large, OMD about one-half as long as distance from eye summit to level of venex margin.

Promesonotal profile gently convex, mesonotum obtusely angulate behind. In profile, basal face of propodeum weakly sinuate; posterior tubercle erect and sharp, about as high as long; posterior declivity nearly straight.

Mandible shiny, costate for nearly entire length. Clypeus and lower face shiny, head distinctly shagreened and less shiny dorsally; mesosoma and gaster similar to upper one-half of head.

Front of head, above level of lower eye margins, with dense appressed pubescence; mesosoma (sparser on sides) and gaster similar. Erect setae as described for Dorymyrmex insanus, except pronotum without discal seta pair.

Color yellowish, head slightly reddish, and last three gastral segments medium brown; appendages yellowish, last flagellar segment brownish.

Neoparatype (mm): HL 0.83-0.91; HW 0.69-0.79; SL 0.83-0.90; EL 0.24-0.27; TL 2.83-3.08. Indices and ratios: CI 83-87; SI 98-100; SI 2 112-114; 01 29-30; OMR 79-81; IOR 130-138.

Neoparatypes agree generally with above description but largest workers with venex margin nearly flat in frontal view; of the 91 paralectotype workers, 27 have at least one (most often two) erect submedian setae on the disc of the pronotum.

Queen
Snelling (1995) - (mm): HL 1.05-1.09; HW 1.05-1.08; SL 0.95-0.97; EL 0.37-0.40; TL 5.74-6.13. Indices and ratios: CI 98-101; SI 87-92; SI2 89-91; 01 35-36; OMR 171-200; IOR 161-172.

Head broadest above eyes, margins weakly convex in frontal view, dorsally broadly rounded onto venex; venex margin nearly flat to weakly convex. Eye margins, in frontal view, coincident with or slightly exceeding head margin; distance from eye summit ro level of venex about two times OMD.

Mesosoma, in dorsal view, about as wide as head. Pilosity about as described for D. insanus but head margins in frontal view with few suberect or erect hairs. Color light yellowish brown, with variable slightly duskier blotches on head and mesosoma; gaster more brownish, terga more yellowish basad and with broad pallid apical margins.