Comprehensive DescriptionRead full entry
So far, A. emarginatus HNS is known only from the Amazon Basin and northward in South America to the Caribbean Coast of Colombia (Parque Tayrona, Magdalena, C. Kugler, and Serrania de Macuira, Guajira Peninsula, W. L. Brown and C. Kugler) and to Trinidad in the east (numerous collections, mainly by N. A. Weber). Although I have taken it several times N and NE of Manaus, I have never found it in the far west of Brasil, in the Tingo Maria area of Amazonian Peru, or the Villavicencio region of cisandean Colombia, and I think it m,ust be rare or local there, if it occurs at all in the western Amazon. Kempf (1972: 21) does record it from as far west as the state of. Rondonia in Brasil: Porto Velho (W. M. Mann).
It is very variable in color and sculpture, but the head is always lighter than the trunk and gaster, contrasting with them. The pronotum may be coarsely or finely striate, usually in a transverse direction, or arched around the front of the disc, but often a greater or lesser part of the disc is smooth and shining (virtually the entire pronotum in a specimen from the Guajira Peninsula of Colombia).
I agree with Kempf (1964: 238) that Emery’ssubsp. rugosus HNS does not represent a separate population in this welter of variation.
Outside of continental South America, in the Caribbean area, the emarginatus HNS complex is represented by a few variants that seem to be distributed allopatrically or parapatrically to one another; i.e., they may behave as unit species of a superspecies. The trouble is that we have very poor samples of most of these forms, and their status remains vague and uncertain in some cases. I am treating them more or less arbitrarily as species here.
A. testaceus HNS : That this is a species apart from emarginatus HNS is indicated by the sharp distinction between their male aedeagi (figs. 74 and 76), at least as shown in worker-associated samples from Grenada Island, which are assumed to be conspecific with the types from nearby St. Vincent. The real problem with testaceus HNS concerns how many of the circum-Caribbean samples that are more or less similar to it in worker characters really belong to it.
The Culebra I. sample assigned by Wheeler (1908) to testaceus HNS is really a distinct species, described  as A. kempfi HNS . The variety nicans, described by Forel from the mountains, of Costa Rica, is similar to A. testaceus HNS in its light ferruginous color, but has more complete striation; its male is unknown. Similar forms from Belize (former British Honduras) in MCZ may belong with very small males, only about half the size of the Grenadan males, but with somewhat similar terminalia. However, these males (from light traps at Hummingbird Gap) are not securely associated with workers, and I do not see what we can safely conclude from them until we know their workers.
Two large workers from the Bonacca Islands, Honduras (M. Bates) have smooth centers to their pronotal discs and smooth upper front faces to the petiolar nodes, and much like typical testaceus HNS from Grenada, but we do not have their males. Likewise, a short series of workers from Nassau, New Providence, Bahamas, are rather extensively striate and have slightly smaller eyes than the Grenada series, but we do not have their males.
Thus, the relationship of testaceus HNS to its Central American and Bahamian vicariants is unknown. My provisional «solution» to this problem is to treat the St. Vincent-Grenada testaceus HNS as one relatively secure species with known male characters. The rest of the Costa Rican, Belizean, Hondurian and Bahamian samples are arbitrarily assigned to A. micans HNS , which is considered as a «form-species» of temporary convenience.
The name A. striatulus HNS is also provisionally applied to the dark brown, very finely striolate form described by Emery under that name as a subspecies of A. emarginatus HNS from Jimenez, in the Atlantic lowlands of Costa Rica. This form, with posterior pronotal disc smooth and shining, has been recaptured in the forest at Rio Toro Amarillo, near Guapiles (W. L. Brown), which is also in the Atlantic lowlands of Limon Province. It may be a separate species; further collections, especially of nests with males, are needed to assess its status.
Possibly some or all of the Central American forms here discusseci (at least the workers) are actually geographical variants of A. emarginatus HNS or A. testaceus HNS , but it is clear that we cannot settle this problem without more evidence.