Eciton burchellii foreli

von Beeren et al. (2018) found the Wasmannian mimic rove-beetles Ecitophya simulans, Ecitomorpha cf. breviceps, and Ecitomorpha cf. nevermanni in colonies of this species in La Selva biological station in Costa Rica. An analysis of cuticular hydrocarbons showed both the ants and beetles had similar CHC profiles. Laboratory behavioral assays showed the beetles sought contact with host ants and often engaged in reciprocal grooming behavior with workers.

Identification
Jack Longino:

Minor worker: head and mesosoma black, metasoma yellow red; occipital tooth small but present; petiolar teeth in the form of short nearly right-angle flanges, either extending onto posterior face of propodeum as separate short carinae, or joined horizontally and forming scoop-like structure, with no descending carina; petiole relatively short and hump-shaped, with no anterodorsal elevated flange; fourth abdominal tergite with short, sparse appressed pubescence beneath erect setae.

Major worker: head and metasoma yellow red, mesosoma also yellow red or variably infuscated with red brown; face densely micropunctate, matte; long sickle-shaped mandibles simple, without tooth on inner margin; other characters as in minor.

Similar species: Eciton burchellii parvispinum.

Jack Longino: There are numerous subspecies of Eciton burchellii. In Costa Rica there are two, Eciton burchellii foreli and Eciton burchellii parvispinum. The workers of foreli have a red brown metasoma, such that minor workers appear bicolored in the field, while the workers of parvispinum have a black metasoma, and the minor workers are entirely black. I can find no other morphological or behavioral feature that correlates with the color difference. The color forms could easily rest on a very small genetic difference, perhaps a single gene. However, the males also exhibit a difference. Males from the Atlantic slope, corresponding to the range of foreli, have a number of long flexuous setae on the scutellum; males from the Pacific slope and the range of parvispinum have the scutellum bare. In most cases this character difference is discrete, but I collected one male that was intermediate. Among a series of males from Monteverde, which is close to the zone of contact of the two forms, one had long setae on one half of the scutellum and the other half was bare (differing across a sagittal plane). All the rest of the males and all of the workers I have seen from Monteverde have the parvispinum phenotype.

Distribution
Jack Longino: The distributions of foreli and Eciton burchellii parvispinum are very sharply parapatric and do not seem to correlate with particular habitats or thermal environments. Eciton b. parvispinum has the broadest distribution, occurring across all of the Pacific slope, from the dry forests of Guanacaste to the rainforest of the Osa Peninsula, from sea level up into the mountains, and dropping a short distance down onto the Atlantic slope, where it meets foreli. For example, on the Barva Transect of Braulio Carrillo National Park, foreli is common from La Selva up to 500m elevation. Above that elevation Eciton burchellii has lower density, but I have three collections from 1400-1500m elevation, about 10km further up-slope, and they are parvispinum. In the Peñas Blancas Valley, east of Monteverde, only foreli occurs at Refugio Eladio, at 800m elevation. At Refugio El Aleman, 950m elevation and 5km further up the valley, I have only collected parvispinum. West of El Aleman, continuing up to Monteverde, only parvispinum is found. Like other examples of step-clines in morphological or genetic characters, it begs the question of what mechanism is maintaining the sharp boundary between these two forms, especially for such large, nomadic organisms.

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Ecuador, Mexico, Panama.

Castes

 * Worker

Nomenclature

 *  foreli. Eciton foreli Mayr, 1886b: 116 (diagnosis in key) (s.w.) PANAMA. Borgmeier, 1936: 154 (q.). Junior synonym of burchellii: Emery, 1896g: 39. Revived from synonymy as subspecies of burchellii: Santschi, 1925d: 222; Borgmeier, 1936: 54. Senior synonym of viator: Borgmeier, 1936: 54. See also: Borgmeier, 1955: 188.
 * viator. Eciton burchelli var. viator Santschi, 1925d: 221 (s.w.) COLOMBIA. Junior synonym of foreli: Borgmeier, 1936: 54.