Crematogaster crucis

I know this species from very few collections. In the lowland wet forest of the Osa Peninsula, I collected workers twice from columns in recent treefalls. Ward collected a nest in Tayrona National Park near Santa Marta, Colombia, at the habitat edge between beach and dry forest. The colony was in 5mm diameter dead twigs of Coccoloba (Polygonaceae). Adult males were found in the nests along with workers and brood. Workers were foraging in the same area as an active Azteca colony. Forel reported that the type specimens were from a hollow branch, “along with Azteca.” Thus two of the few known collections were collected with Azteca, raising the possibility of a specialized association. (Longino 2003)

Identification
Longino (2003) - Costa Rican material, the type specimens, and additional material from the type locality are very similar. This species exhibits the general habitus of the crinosa complex, and in particular the face has sparse erect setae over short appressed pubescence, but it differs in having long flexuous setae on the mesosoma and fourth abdominal tergite. In Costa Rica there is no other species with which it can be confused.

Distribution
Longino (2003) - Colombia, Costa Rica.

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Costa Rica, Ecuador.

Nomenclature

 * . Crematogaster brevispinosa r. crucis Forel, 1912f: 212 (w.) COLOMBIA.
 * Type-material: syntype workers (number not stated).
 * Type-locality: Colombia: Magdalena, Santa Cruz, nr Santa Marta (A. Forel).
 * Type-depository: MHNG.
 * Combination in C. (Orthocrema): Emery, 1922e: 134.
 * Subspecies of brevispinosa: Forel, 1914d: 270; Bruch, 1915: 530; Bruch, 1916: 303; Emery, 1922e: 134; Gallardo, 1934: 12 (redescription); Kusnezov, 1953b: 337; Kempf, 1972a: 85; Bolton, 1995b: 151.
 * Status as species: Longino, 2003a: 53 (redescription); Pedraza & Fernández, 2019: 895.
 * Distribution: Colombia, Costa Rica.

Longino (2003) - In addition to the material reported here as crucis, I have examined three collections (departments of Valle and Choco in Colombia, Madre de Dios in Peru) that are obviously related to crucis, with the same habitus and long flexuous setae on the fourth abdominal tergite, but differing in details of sculpture and pilosity. Further collections will be necessary to assess whether this is best interpreted as intra versus interspecific variation.

Worker
Longino (2003) - HL 0.707, 0.549, 0.632; HW 0.762, 0.588, 0.679; HC 0.741, 0.555, 0.649; SL 0.480, 0.394, 0.450; EL 0.160, 0.138, 0.154; A11L 0.241; A11W 0.138; A10L 0.119; A10W 0.133; A09L 0.058; A09W 0.081; A08L 0.039; A08W 0.069; WL 0.764, 0.570, 0.681; SPL 0.109, 0.081, 0.100; PTH 0.164, 0.134, 0.162; PTL 0.201, 0.137, 0.178; PTW 0.217, 0.176, 0.206; PPL 0.185, 0.141, 0.153; PPW 0.207, 0.162, 0.176; CI 108, 107, 107; OI 23, 25, 24; SI 68, 72, 71; PTHI 82, 98, 91; PTWI 108, 128, 116; PPI 112, 115, 115; SPI 14, 14, 15; ACI 1.62.

Color varying within populations, uniformly orange brown, or bicolored with orange brown head and mesosoma and darker gaster, or uniformly dark red brown; workers of relatively uniform small size, lacking pronounced size polymorphism.

In face view head subquadrate, with emarginate posterior margin; mandibles smooth and shining with sparse large puncta; clypeus smooth and shiny or faintly etched; scapes short, in face view not attaining posterior margin of head when laid back; antennal club two-segmented; scapes with subdecumbent pubescence, with no differentiated long erect setae; face with sparse appressed to subdecument pubescence and sparse long erect flexuous setae; face smooth and shining.

Promesonotal profile forming a single continuous arch; dorsal face of propodeum short, visible in dorsal view; lateral carinae bridge propodeal suture such that in lateral view suture not visible, lateral profile forms a single sloping declivity from about middle of mesonotum to petiolar insertion; propodeal spines short, upturned; promesonotal dorsum and sides of pronotum completely smooth and shining, katepisternum with medial space smooth and shining, variable development of weak puncta and rugulae around edges; dorsal face of propodeum (a narrow transverse strip forming posterior wall of propodeal suture and extending onto bases of propodeal spines) rugulose; posterior face of propodeum smooth and shining; lateral face of propodeum largely smooth and shining, with faint longitudinal rugulae ventrally; mesosomal dorsum covered with subdecumbent long pubescence, pronotal humeri each with a long flexuous seta, pairs of shorter erect setae variably present on anterior mesonotum, posterior mesonotum near propodeal suture, and sides of propodeum midway between propodeal suture and propodeal spine; femora and tibiae with appressed pubescence, no erect setae.

Petiole in lateral view subtriangular, with slightly convex dorsal face, completely smooth and shining; anteroventral petiolar tooth strongly developed, anteriorly projecting, long and thin but with blunt tip; dorsal face of petiole smooth and shining, about as wide as long, with convex sides, widest about one third distance from anterior margin, posterolateral tubercles with a few short appressed hairs, occasionally with an inconspicuous longer suberect hair; postpetiole lacking ventral tooth, dorsum globular, smooth and shiny, with a few erect hairs; fourth abdominal tergite smooth and shining, somewhat lanose, with abundant pilosity that is a combination of suberect and subdecumbent long flexuous hairs.

Type Material
Longino (2003) - Syntype workers: Colombia, Magdalena, Santa Cruz near Santa Marta, in a hollow branch, along with Azteca (Forel) (examined).

References based on Global Ant Biodiversity Informatics

 * Adams B. J., S. A. Schnitzer, and S. P. Yanoviak. 2016. Trees as islands: canopy ant species richness increases with the size of liana-free trees in a Neotropical forest. Ecography doi: 10.1111/ecog.02608
 * Adams B. J., S. A. Schnitzer, and S. P. Yanoviak. 2019. Connectivity explains local ant community structure in a Neotropical forest canopy: a large-scale experimental approach. Ecology 100(6): e02673.
 * Cuezzo, F. 1998. Formicidae. Chapter 42 in Morrone J.J., and S. Coscaron (dirs) Biodiversidad de artropodos argentinos: una perspectiva biotaxonomica Ediciones Sur, La Plata. Pages 452-462.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Gallardo A. 1934. Las hormigas de la República Argentina. Subfamilia Mirmicinas, segunda sección Eumyrmicinae, tribu Crematogastrini (Forel), género Crematogaster Lund. Anales del Museo Nacional de Historia Natural de Buenos Aires 38: 1-84.
 * INBio Collection (via Gbif)
 * Longino, J.T. 2003. The Crematogaster (Hymenoptera, Formicidae, Myrmicinae) of Costa Rica. Zootaxa 151:1-150