Strumigenys mixta

While some of the type material was taken from orchid plants in quarantine, suggesting this species is arboreal, collections since have been made from litter or ground sampling. These have been from a range of forest habitats. The native range is Central and northern South America, with introduced populations in Arizona, United States.

Identification
Bolton (2000) - A member of the Strumigenys louisianae-group. Immediately identified by its possession of fine flagellate hairs at all the positions mentioned. No other species of the group has this arrangement. One (Strumigenys dubitata) has no flagellate hairs at all and Strumigenys louisianae only has them at the humeral angles of the pronotum.

Distribution
Strumigenys mixta has a spotty a native range from Venezuela to southern Guatemala and was most likely introduced in the USA. It has been collected several times among ornamental, irrigated landscapes at the University of Arizona, Pima, Arizona, and in residential areas of Yuma and Phoenix (Booher, 2021).

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Costa Rica, Guatemala, Honduras, Venezuela.

Nomenclature

 *  mixta. Strumigenys mixta Brown, 1953e: 4 (w.) GUATEMALA. See also: Bolton, 2000: 526.

Worker
Holotype worker: TL 2.32 mm., HL 0.54 mm., ML 0.31 ram., WL 0.54 ram., CI 83, MI 57.

Differs significantly from Strumigenys louisianae only in the following details:

(1) Inner mandibular border with an extra minute denticle slightly basad of the apical third of the ML.

(2) Pilosity decidedly narrower and less conspicuous, especially on the posterior cephalic dorsum. Paired, outstanding hairs, one on each lateral occipital border, each humeral angle and each side of the mesonotum are all finely flagelliform, whereas in S. louisianae, the lateral occipital and mesonotal hairs are stiff and spatulate towards their apices.

(3) Metanotal groove completely or very nearly completely obsolete; in profile from lateral view, the posterior alitruncal dorsum continuous in outline, not interrupted by the notch at the metanotal groove as in S. louisianae.

Color light ferrugineous yellow.

Paratypes. TL 2.14-2.49 mm., HL 0.51-0.59 mm., ML 0.28-0.32, WL 0.51-0.60, CI 80-84, MI 54-60. The Escuintla (type nest) series is made up of mostly smaller, yellow individuals, while that from San Jos contains, workers mostly in the upper part of the size range given and medium ferrugineous or deep burnt-orange in color. Means of dimensions, but not of proportions, differ slightly, but there is also an absolute overlap. The color difference is not considered taxonomically significant in the face of similar variation seen in many other dacetine species.

Bolton (2000) - TL 2.1-2.5, HL 0.51-0.59, HW 0.43-0.46, CI 80-84, ML 0.28-0.32, MI 54-60, PW 0.25-0.30, AL 0.51-0.60 (3 measured). Mandible with a minute inconspicuous denticle proximal to the preapical tooth, located on the upper inner margin just distal of its midlength. With head in profile postbuccal groove shallow and obtuse. Apicoscrobal hair finely flagellate. Cephalic dorsum with 2 pairs of short standing hairs, one close to occipital margin, the other close to highest point of vertex. Pronotal humeral hair elongate, fine and flagellate; mesonotal standing hairs flagellate. Ventral surface of petiole with a minute spongiform lobe at the extreme posteroventral angle below the node; when postpetiole flexed downward this lobe is concealed between the ventral lobes of the postpetiole.

Type Material
Holotype (USNM) one of 15 workers taken at Escuintla, Guatemala (W. M. Mann leg.). Paratypes: 14 workers from type nest series, same data as for holotype, and 5 workers from orchid plants (Cattleya bowringeana) shipped from San Jose, Guatemala and intercepted in U.S. Plant Quarantine at San Francisco, California (SF 20739 Supl.; 46-5348). Deposited in USNM and MCZ.

Bolton (2000) - Holotype and paratype workers, GUATEMALA: Escuintla, v.1924 (W. M. Mann); paratype workers, GUATEMALA: San Jose, 12.iv.1946, SF 20139 Supl., 46-5348 (intercepted by U.S. Plant Quarantine at San Francisco, California), in shipment of orchids (Cattleya bowringeana) (no collector's name) [examined].

Etymology
The name mixta refers to the intermediate characters, seemingly linking S. louisianae and Strumigenys emeryi Mann, but also distinguishing this species from both.

References based on Global Ant Biodiversity Informatics

 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).