Acromyrmex ameliae

A social parasite of Acromyrmex subterraneus and Acromyrmex subterraneus brunneus.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Biology
This ant is a social parasite in the nest of Acromyrmex subterraneus. The form of Social Parasitism is an inquiline with queens and workers smaller than their host.

Nomenclature

 *  ameliae. Acromyrmex ameliae De Souza, Soares & Della Lucia, 2007: 252, figs. 1, 3, 5, 7, 9-14 (w.q.) BRAZIL.

Worker
HL = 0.6; HW = 0.7; ML = 0.3; WL = 0.9; SL = 0.8; ED = 0.1.

We verified that the distance from spiracle to bulla relative to pronotum width differed significantly among the minor workers of host and parasite (F1, 298 = 551.36, P < 0.01). Two groups are clearly shown in Figure 15: one had a small number (n = 25) of parasite workers and another formed by a large number of host minor workers (n = 275). The fact that the workers sorted into two groups, as well as morphological differences between the groups, is highly suggestive. We found some A. ameliae workers are larger than host minors but this is because larger host minors were not sampled. Preliminary genetic analysis by RAPD (Random amplified polymorphic DNA) markers clearly shows differences between the two groups, confirming these results. As in Acromyrmex insinuator, the workers of A. ameliae have a significantly smaller distance from their spiracle to bulla than their host minor workers of same pronotum width (Figs. 16 and 17). These results are almost identical to those obtained by Sumner et al. (2003) for A. insinuator.

Queen
This species has a palpal formula of 4, 2 and 11 antennal segments as is typical for attine ants. Acromyrmex ameliae queens have large and convex eyes and the inferior pronotal spines are straight and forward-positioned as in the host species. The color of the analyzed parasite queens vary from brownish to brownish-black and this is not associated with the subspecies of host ants since one can find queens of the parasite of either color in a single nest. Worker color is the only character that is presently used to separate the two host subspecies: Acromyrmex subterraneus and Acromyrmex subterraneus brunneus. The latter has a brownish-black color whereas the former is light brown to yellow (Gonçalves, 1961). The queens of A. ameliae are much smaller than those of its hosts, with a WL ~ 0.6 as great. Acromyrmex ameliae further has a more abundant pilosity with thicker and longer hairs on the gaster, on the dorsal portion of the alitrunk and on the anterior portion of the head, in comparison to that on the host subspecies. The parasite queen also has prominent ridges on the head and on the first segment of the gaster and expansions on the anteroventral margin of the postpetiole that are not seen on the host subspecies. The tubercles on the gaster of A. ameliae are more or less ordinated in four longitudinal lines similar to the host species. However, these tubercles are very much reduced and less prominent when compared to those of the hosts.