A New Species of Neotropical Carpenter Ant in the Genus Camponotus (Hymenoptera: Formicidae), Apparently without Major Workers

We describe a new species of carpenter ants from Ecuador, which apparently has an obligatory relationship with the ant plants Cecropia membranacea Trécul, C. herthae Diels and C. marginalis Cuatrec. The workers are relatively small and hairy, and based on a number of collections, it does not appear to have major workers. We compare the new species to Camponotus balzani, to which it appears to be similar and which has normal major workers, and also lives in Cecropia spp.


Introduction
Camponotus carpenter ants have a worldwide distribution and form one of the hyperdiverse genera together with Pheidole [1]. It is still unknown which of these two largest genera has the greater number of species as many new species await discovery. In the New World, about 650 taxa have been named in Camponotus, which will be reduced to about 440 valid species, including about 140 new species (Mackay, unpublished, manuscript available at http://www.utep.edu/leb/antgenera.htm). Other species of neotropical Camponotus have been recently described [2][3][4].
The revision of such a large group has taken nearly 20 years, with several more needed to complete the work. Occasionally names are needed for ecological studies, which cannot wait the completion of the entire work. We here describe an interesting new species to provide a name for an ant whose interaction with Cecropia will be described by the junior author in future papers.
This species is unusual in that the workers appear to be monomorphic. The majority of the carpenter ants are dimorphic, but monomorphic workers are also found in the montivagus species complex [5,6], subgenus Dendromyrmex [7], and some of the species in the subgenus Myrmobrachys are only weakly dimorphic.
Placement of this species into a subgenus is difficult because of the lack of major workers. Based on its similarity to C. balzani and several characters listed below, we placed it in the subgenus Tanaemyrmex. The clypeal carinae of the minor worker, female, and to some extent the male are well developed. The sides of the clypeus diverge anteriorly in all three castes. The head of the minor worker is longer than broad, with large eyes that reach the sides of the head. The minor worker is relatively large, with an elongated mesosoma, which is typical for the subgenus Tanaemyrmex. The dorsum of the mesosoma of the minor is convex and rounded and somewhat angulate between the two faces. The propodeal spiracle is elongated. The petiole is somewhat thickened (viewed from side). Appressed pubescence is sparse. The head and mesosoma are coriaceous, and the gaster is finely striolate. These characteristics are similar to most other species considered to be in Tanaemyrmex.

Materials and Methods (Measurements and Indices)
At least ten individuals of each of eight species of Cecropia were found that were at least 100 m apart. The exceptions were C. litoralis Snethl, in which only two individuals were found and C. marginalis where eight plant individuals were collected. Camponotus reburrus was found in saplings of Cecropia membranacea and C. marginalis, but the majority of samples came from C. herthae. Seventy-five Cecropia individuals were collected, and C. reburrus was found in 9.3% of the trees collected. Specimens were measured using an ocular micrometer in a dissecting microscope.

Results
The new species is characterized as follows.
Diagnosis. The minor worker of C. reburrus is a relatively small (4.4-6.6 mm total length) yellowish brown specimen, with a transversely striped yellow and brown gaster, or at least with yellow lateral splotches. The sides of the head are straight and parallel, and the carina on the clypeus is well marked. The antennal scape has numerous erect hairs along the shaft, the hairs on the tibiae are coarse and suberect. Most surfaces are moderately to strongly shining.
The female of C. reburrus is a small (total length 6-7 mm) hairy specimen, which is shiny dark brown with lighter colored legs. The gaster has lateral yellow splotches. The sides of the head are straight and parallel. The size and abundant 1 mm Figure 1: Mesosoma, petiole, and first gastral tergum of a minor worker of C. reburrus (Napo, Ecuador). The male of C. reburrus is a small (total length 4.0-5.5 mm) dark brown to yellowish brown specimen, with abundant hairs on most surfaces. Other than color and hairiness, it does not seem to possess characteristics which would distinguish it from other small males of Camponotus.

mm
The major worker apparently does not exist.   Ferrugineous red, gaster with yellow lateral splotches ranging to striped brown and yellow. Clypeus with carina poorly developed; anterior clypeal border concave, medial portion meeting lateral portion in rounded angle; frontal carinae closely placed; eyes large, extending past sides of head; scape short, extending past posterior lateral corner of head by 1.5 funicular segments; head elongate, rectangular with nearly parallel sides; posterior margin convex, rounded; mesosoma elongate; pronotum lengthened and lowered in profile; metanotal suture deep, propodeum lower than remainder of mesosoma, rounded; petiole thick in profile.

Description of the
Erect hairs abundant, about 20 scattered over surface of clypeus, 5-6 on cheek, 5 or more on malar area, erect hairs on posterior margin and posterior lateral corner of head, scape with two distinct types of hairs, erect (or nearly erect) longer (0.13 mm) hairs, and not very abundant (fewer than 10, excluding similar hairs at apex), and suberect short (>0.08 mm) abundant (about 100) hairs, pronotum with long (0.4 mm) erect hairs along posterior border, erect hairs scattered on dorsum of remainder of mesosoma, petiole and gaster, femora with several nearly erect hairs, tibiae with numerous hairs that are mostly suberect; appressed pubescence sparse, short on head (0.02 mm), longer on gaster (0.06 mm).
Sculpture finely coriaceous, but strongly shining. Color predominantly dark brown, legs lighter brown, coxae, trochanters and base of tibiae yellow, gaster with lateral yellow blotches on each tergum.   Mandible without teeth, except apical angle; anterior border of clypeus broadly convex, clypeal carina poorly defined, but present; sides of head anterior to eyes concave, nearly parallel, posterior border of head broadly rounded, concave between ocelli; scape extending approximately 1/2 length past posterior lateral corner of head; eye large, occupying approximately 1/2 length of side of head; ocelli well developed; propodeal spiracle oval shaped; petiole thick when viewed in profile, apex slightly flat but convex as seen from front.
Erect and suberect hairs present on mandibles, clypeus, dorsum and ventral surfaces of head; sides of head, posterior border of head, dorsum of mesosoma, legs, petiole, and all surfaces of gaster; appressed hairs sparse few present on head, mesosoma, and gaster.
Distribution. Known only from northeastern Ecuador.    Etymology. From Latin, reburrus, meaning one with bristling hair, referring to the hairs on the head.
Comments. Camponotus reburrus does not appear to be closely related to any of the other described species in the subgenus Tanaemyrmex, other than C. balzani. This close relationship with C. balzani was further supported with DNA barcode analyses (Barriga, unpublished information).The minor workers can be separated in that the side of the head has few erect or suberect hairs (abundant in minors of C. balzani), the gaster is transversely striped with yellow bands (generally concolorous light brown in C. balzani, sometimes with a hint of tan transverse stripes), and the workers are slightly smaller (much overlap in size ranges in the two species). The females of C. reburrus are much smaller (maximum total length approaches 7 mm) than those of C. balzani (total length over 1 cm). The splotches or stripes on the gaster are definitely yellow in females of C. reburrus but are only pale brown (if present) on the gaster of females of C. balzani. The males of C. reburrus are also much smaller (total length approaching 4.7 mm) as compared to the males of C. balzani (total length greater than 5 mm). The males of C. reburrus are generally darker brown than the pale medium brown males of C. balzani. If major workers are found to exist, they will probably be similar to those of C. balzani with the sides of the head narrowed anteriorly, with a welldeveloped clypeal carina, but differing in having few erect hairs on the sides of the head. The gaster would be expected to have well-developed yellow splotches or bands, which