Acropyga romeo

A. romeo was collected from leaf litter samples in Dicymbe dominated forest that also contained Acropyga stenotes, but otherwise nothing is known of its natural history. (LaPolla 2004)

Identification
LaPolla (2004) - Worker: 9 segmented antennae; mandible with 4 teeth; 4th tooth very small and offset from masticatory margin; head longer than broad, becoming narrower toward anterior end; small species (total length: < 1.5 mm). Queen: unknown. Male: unknown. Compare with Acropyga exsanguis, Acropyga keira and Acropyga smithii.

This species can be confused with Acropyga exsanguis and Acropyga keira. In all specimens of A. exsanguis examined in this study, the species always has had only 3 teeth on the mandible, with no sign of a smaller offset basal tooth as seen in A. romeo. A. keira also has only be observed to possess 3 teeth on its mandibles, and it has very short appressed hairs on its mesosoma, as opposed to the longer hairs observed in A. romeo. Finally both A. exsanguis and A. keira are larger species.

This species appears to belong to the decedens species-group, though until males are associated with workers its phylogenetic placement in the genus remains problematic. The combination of a narrow, 4-toothed mandible and a narrow, hairy clypeus suggests placement in the species group. This is among the smallest of the New World Acropyga species, around the same size as Acropyga smithii and ''Acropyga panamensis.

Key to New World Acropyga Workers

Distribution based on Regional Taxon Lists
Neotropical Region: Guyana.

Acropyga romeo species is known only from its type locality at the base of Mt. Ayanganna in western Guyana.

Castes
Known only from the worker caste.

Nomenclature

 * . Acropyga romeo LaPolla, 2004a: 57, fig. 23 (w.) GUYANA.

Worker
(n=4): TL: 1.41-1.44; HW: 0.334-0.351; HL: 0.384-0.402; SL: 0.242-0.266; ML: 0.371-0.402; GL: 0.621-0.67; CI: 85.32-90.23; SI: 70.20-79.64.

Head: yellow; covered in a layer of short appressed hairs; head longer than broad, becoming narrower toward anterior end; posterior margin entire; 8-9 segmented, incrassate antennae; scape fails to reach posterior margin by about length of first 2 funicular segments; clypeus narrow, medially convex, covered in a dense layer of hairs; mandible narrow, with 4 teeth; apical tooth often much longer than other teeth; basal tooth very small, offset from masticatory margin; gap exists between anterior clypeal margin and inner mandibular margin. Mesosoma: yellow; in lateral view, pronotum rises steeply toward mesonotum; pronotum with a layer of appressed hairs and scattered erect hairs posteriorly; mesonotum at about same height as propodeum; mesonotum with layer of appressed to erect hairs; metanotal area distinct; propodeum short and flat, with appressed to erect hairs; declivity steep. Gaster: petiole thick and erect, slightly surpassing height of propodeal spiracle; gaster yellow; covered in dense layer of appressed hairs, with scattered erect hairs throughout.

Type Material
Holotype worker, GUYANA: Camp on Potaro River at base of Mt. Ayanganna, N 05" 18.08;W 0590 54.67, elev. 695 m +/-13 m (J.S. LaPolla et al.) (UGBC); 3 paratype workers, same locality as holotype (USNM) (MCZC). The holotype is labeled JSL TYPE # 106.

Etymology
Named in honor of Romeo Williams with admiration and thanks. Romeo is a Guyanese field guide and naturalist who made my 3 month expedition to Guyana in the autumn of 2002 in search of Acropyga and other ants possible. The name is treated as a noun in apposition.

References based on Global Ant Biodiversity Informatics

 * Franco W., N. Ladino, J. H. C. Delabie, A. Dejean, J. Orivel, M. Fichaux, S. Groc, M. Leponce, and R. M. Feitosa. 2019. First checklist of the ants (Hymenoptera: Formicidae) of French Guiana. Zootaxa 4674(5): 509-543.
 * Groc S., J. H. C. Delabie, F. Fernandez, M. Leponce, J. Orivel, R. Silvestre, Heraldo L. Vasconcelos, and A. Dejean. 2013. Leaf-litter ant communities (Hymenoptera: Formicidae) in a pristine Guianese rainforest: stable functional structure versus high species turnover. Myrmecological News 19: 43-51.
 * LaPolla J.S. 2004. Acropyga (Hymenoptera: Formicidae) of the world. Contributions of the American Entomological Institute 33(3): 1-130.
 * Lapolla, J.S., T. Suman, J. Soso-Calvo and T.R. Schultz. 2006. Leaf litter ant diversity in Guyana. Biodiversity and Conservation 16:491510