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Costa Rica: northern Pacific lowlands.
Mycetosoritis is a small genus of attines with few species and restricted geographic distribution (Wheeler 1907, Kempf 1968, MacKay 1998). Three species occur in southern Brazil and Argentina, and two species occur in Central and southern North America. Mycetosoritis hartmanni, described by Wheeler in 1907, occurs in southern Texas. I collected it once at the Laguna Atascosa Wildlife Refuge, a coastal habitat at the southernmost tip of Texas. In low shrubby vegetation on a sand ridge overlooking the ocean I found a small colony beneath shrubs. The nest was in the soil, with a 1-2cm tall symmetrical turret over the entrance. I found aggregations of workers in small chambers 5-10cm deep, but I failed to find a queen or any brood. Mycetosoritis vinsoni, described by MacKay in 1998, occurs in Costa Rica. The type locality for M. vinsoni is the Lomas Barbudal reserve in Guanacaste Province, and when described it was known from a single worker. Jenny Jacobs, a student working on the ant fauna of the small islands of Costa Rica's northern Pacific coast, found them relatively frequently in Winkler samples of sifted leaf litter. Ulrich Mueller has collected it in Santa Rosa National Park. MacKay has seen additional collections of Mycetosoritis from eastern Mexico (pers. comm.). It is possible that the lineage occurs in seasonally dry habitats from southern Texas to Costa Rica.
MacKay differentiated vinsoni from hartmanni by the lack of anteromedian tubercles on the pronotum and the more curved setae on the scape of vinsoni. I find the two to be extremely similar ants (Figure), and there is no evidence to favor interspecific over intraspecific variation. On my one collection of hartmanni from Texas there are anteromedian tubercles, as illustrated by MacKay, but the scape hairs are relatively more curved than his figure. On the collections of vinsoni I have seen from Costa Rica there are also anteromedian pronotal tubercles, and the scape hairs are similarly curved. Thus, I see almost no difference between Texas and Costa Rica specimens. There are too few collections to show zones of sympatry or parapatric distributions of discrete morphological forms. My philosophy is that conspecificity is a null hypothesis that should be assumed until statistically rejected, and if this were a formal publication I would synonymize vinsoni under hartmanni.
Kempf, W. W. 1968. Miscellaneous studies on Neotropical ants. IV. (Hymenoptera, Formicidae). Stud. Entomol. 11:369-415.
MacKay, W. P. 1998. Dos especies nuevas de hormigas de la tribu Attini de Costa Rica y Mexico: mycetosoritis vinsoni y mycocepurus curvispinosus (hymenoptera: formicidae). Revista de Biologia Tropical 46:421-426.
Wheeler, W. M. 1907. The fungus-growing ants of North America. Bull. Am. Mus. Nat. Hist. 23:669-807.
Found most commonly in these habitats: 2 times found in dry forest.
Elevations: collected at 20 m
Collect Date Range: collected between 2002-06-18 and 2002-06-20