Technomyrmex difficilis

Fernández and Guerrero (2008) - A tramp species detected in the New World at the zoo in Washington and outdoors in Florida and Puerto Rico (Bolton 2007 and personal communication).

Identification
Closely related to Technomyrmex albipes but separated by the presence of setae on the dorsum of the head behind the level of the posterior margin of the eye (never developed in albipes) and by having the promesonotum somewhat longer and more slender, DTI 127 – 135 (as opposed to DTI I 10- 124 in albipes). This species has been confused many times with albipes, and isolated specimens with the characteristic cephalic setae abraded away are difficult to identify. In such specimens the eye may give a clue to the correct identity because in general, with the head in full-face view the eye in albipes workers is flatter and less convex than in difficilis so that the outer margin usually just fails to break the outline of the side of the head in the former but distinctly interrupts the outline of the side in the latter. There is some variation of this feature in both species. Additionally, the mesonotum generally has a pair of setae present in difficilis whereas mesonotal setae are generally absent in albipes. Again this character is variable because difficilis samples are known where mesonotal setae are lacking and albipes samples are known in which a pair is present.

Of all the material examined a few specimens from Madagascar and one specimen from U.S.A. had an extra pair of short setae on the dorsum of the head, behind the universally present pair. Whether these are genuine workers or the most worker-like form of intercaste remains to be seen. These individuals may resemble Technomyrmex pallipes in this character but samples of the latter always have the middle and hind femora and tibiae distinctly lighter in colour than the mesosoma and do not have tarsi that are much paler than the tibiae. Malagasy material of difficilis tends to differ slightly from that of the rest of the world. The cuticle of the head and mesosoma is somewhat more glossy, the angle through which the propodeal dorsum meets the declivity is blunter and setae on the first gastral tergite are shorter. These differences seem consistently to isolate the Malagasy population, but at present I am not convinced that they are sufficient to justify separation at species-rank T. difficilis was originally described as a race of Technomyrmex mayri, but the two are quite different. T. difficilis is a smaller species with shorter scapes, relatively larger eyes and a shorter, more compact mesosoma (compare measurements and indices). In addition, the metathoracic spiracles of mayri, m dorsal view, do not abut the metanotal groove, and the propodeal dorsum is longer, its straight-line length in profile is greater than the have setae that arise above the level of the spiracfe whereas such setae are always present in difficilis.

Fernández and Guerrero (2008) - This species is separated from others in the New World by morphological traits such as dorsum of head behind posterior margin of eye with a single pair of setae and tarsus of hind leg distinctly lighter than the tibia.

Distribution based on Regional Taxon Lists
Afrotropical Region: South Africa. Australasian Region: Australia. Indo-Australian Region: Borneo, Hawaii, Indonesia, Krakatau Islands, Malaysia, New Guinea, Philippines, Singapore, Timor-Leste. Malagasy Region: Madagascar, Seychelles. Nearctic Region: United States. Neotropical Region: Antigua and Barbuda, Honduras, Jamaica, Lesser Antilles, Puerto Rico, Saint Kitts and Nevis. Oriental Region: Laos, Thailand, Vietnam.



Biology
Bolton (2007) - In his unpublished thesis Warner (2003) succinctly summarises the nature of difficilis (misidentified as albipes in the study) as an invasive in Florida, U.S.A. He says that it “nests at or above ground level in numerous locations within the landscape, home and suburban woodland habitats. Nests are frequently found in trees and bushes, tree holes, under palm fronds and old petiole bases, under leaves on trees, in loose mulch, under debris, in leaf-litter, both on the ground and in rain gutters, wall voids, and attics. Nests tend to be found outside of structures more than inside.” He points out that its main foods are plant nectar and honeydew but that the ants will also feed on dead insects and other protein. In houses they forage most commonly in kitchens and bathrooms, the best sources of food and water, as well as on exterior structures. Like some other species in the group (e.g. Technomyrmex pallipes, Technomyrmex jocosus) they have been found nesting in electrical fixtures. Outdoors, workers of this species are most commonly encountered on vegetation although, like most or maybe all other species in the albipes group, they also nest and forage terrestrially.

Worker-queen intercastes are produced in difficilis, and according to Warner (2003, unpublished thesis) these may make up nearly half the colony. Intercastes have reproductive functions and are not usually found outside of nests; foraging behavior appears to lie strictly in the domain of true workers. As is known in several other species of the albipes group ergatoid males, as well as the usual alates, are produced by difficilis. The alate males mate with alate queens in the usual nuptial flight, which intiates new nests. The queens of these colonies eventually die off and are replaced by reproductive worker-queen intercastes, all grades of which have spermathecae (absent from true workers) and they mate with ergatoid males. Nests in this condition then multiply by fission and produce polydomous colonies that are later able to produce new generations of alate queens and males.

Nomenclature

 *  difficilis. Technomyrmex mayri r. difficilis Forel, 1892l: 242 (w.q.) MADAGASCAR. Raised to species and senior synonym of nitidulans: Bolton, 2007a: 47.
 * nitidulans. Technomyrmex mayri st. nitidulans Santschi, 1930a: 72, figs. 31-33 (w.) MADAGASCAR. Junior synonym of difficilis: Bolton, 2007a: 47.

Worker
Bolton (2007) - TL 2.4 - 3.1, HL 0.57 - 0.76, HW 0.52 - 0.69, SL 0.52 - 0.74, PW 0.36 - 0.47, WL 0.74 -1.02 (35 measured). Indices: CI 89 - 97, SI 95 - 107, OI 25 - 30, EPI 72 - 86, DTI 127 - 135.

Frontal carina with 2 (very rarely 3) setae: in profile the first above the torulus, the second at about the level of the antenor margin of the eve; when a third seta present it is between these two. Dorsum of head posterior to this with a single pair of setae, in profile located just over half way between level of posterior margin of eye and posterior margin of head, not at the posterior margin; this pair of setae distinctly shorter than the posteriormost seta on the frontal carina (see notes below). Anterior clypeal margin with a very weak, shallow median indentation. With head in full-face view the sides shallowly convex and the posterior margin with a small shallow indentation medially. Eyes located in front of midlength, EPI < 90; outer margin of eye breaks the outline of the side. Number of setal pairs on mesosoma: pronotum 1 - 2; mesonotum 0 – 1 (usually 1); propodeal dorsum 0; lateral margins of propodeal declivity 1 - 2, above the level of the spiracle. With mesosoma in profile the mesonotal outline is evenly curved, without a distinct step or angle in the outline that defines conspicuous dorsal and declivitous faces. Dorsum of propodeum short in profile and meeting the declivity in an angle; length of dorsum less than depth of declivity to spiracle. In dorsal view the metathoracic spiracles are very close to, or abut, the metanotal groove. Gastral tergites 1 - 4 each with numerous setae, distributed everywhere on the sclerites; maximum length of setae on first gastral tergite is usually slightly less than the maximum diameter of the eye but sometimes the two are subequal. Head, mesosoma, petiole and gaster dark brown to black; in profile the gaster may be slightly lighter than the mesosoma. Coxae, femora and tibiae the same colour as the mesosoma or slightly lighter; never with strongly contrasting lighter coxae. Tarsi of middle and hind legs yellowish white to yellow, distinctly paler than the tibiae.

Type Material
Bolton (2007) - Syntype workers and queen, Madagascar: Noslbe, Village de l'Imerina (Sikora) [examined].



Determination Clarifications
Bolton (2007) - In recent synoptic works on the Australian ant fauna that mention albipes, that of Shattuck (1999) is most probably difficilis, and the unnamed species of Andersen (2000) is certainly difficilis as his figure 29 has the right proportions and clearly shows the posteriorly placed pair of setae on the head. T. difflcilis has also successfully colonised the state of Florida, U.S.A., where it was first described, as albipes, by Deyrup (1991) and later included under that name by Vail, Davis, et al. (1994) and Deyrup, bavis & Cover (2000). It also seems probable that a proportion of the material listed as albipes by Wilson & Taylor (1967) will be difficilis.