Bariamyrma hispidula, Lattke, 1990

Lattke, J., 1990, A new genus of myrmicine ants (Hymenoptera: Formicidae) from Venezuela., Entomologica Scandinavica 21, pp. 173-178 : 174-177

Bariamyrma hispidula sp. n.

(Figs. 1-4)

Type material. - Holotype [[ queen ]], Venezuela: Amazonas, Cerro de la Neblina Basecamp , 0°50'N 66°10'W, 140 m, flight intercept pan trap in rainforest, 21- 28.11.1985, P. J. Spangler. In the Instituto de Zoologia Agricola collection, Universidad Central de Venezuela, Maracay, Venezuela .

Description

Holotype female (Fig. 1). - Dimensions: HL 1.34, HW (excluding eyes) 1.17, ED 0.33, ML (straight line distance along external margin from insertion to anteriormost margin) 0.73, SL 0.95, WL 2.03 mm, CI 0.87, SI 0.81, MI 0.63.

Head (Fig. 2) in full face view with posterior margin broadly convex, sides more or less parallel. Clypeus with transverse rugae. Eyes large and prominent, situated at cephalic midlength, 3 well developed ocelli present at vertex. Dorsolateral mandibular surface rugulose, but smooth and shining about the chewing and basal margins. Dorsal cephalic sculpture between frontal carinae longitudinally porcate. Frontal lobes anteriorly thin and lamellar, partially raised and leaving the basal condyles partially exposed in frontal view. Basal antennal sclerite partially covering part of the basal condyle, condylar constriction sharp, forming an obtuse angle with an oblique basal flat surface of the scape. Antennal fossae deep, laterally bordered by more or less parallel rugulae that become more irregular between the eye and frontal carina and posterad. Flexor surface of scape with a broad sul-

cus, scape slightly bent basally, expanding apicad. Scape with longitudinal costulae; funicular segments colliculate. Cephalic ventrum with a median carina, and medially smooth and shining.

Pronotal collar with imbricate microsculpture. Frontal pronotal surface transverse porcate, anterolaterally with an excavate area of smooth sculpture behind the lower occipital corners of the head. Pronotum with a lateromedian depression and with a convex posterior lobe; sculpture porcate-rugose. Humeri bluntly angulate in dorsal view. Mesonoturn longitudinally rugose. Anepisternum with transverse rugae, divided from katepisernum by a broad and deep sulcus. Katepisternum with transverse rugae but more sharply defined than in the anepisternum, with broader and shallower areas between them. Carinae on metapleuron and lateral propodeal face as in anepisternum, slightly more effaced. Propodeal spiracle large and rounded, facing obliquely caudad. Suture before scutellum broad and with two median concave depressions. Scutellum roughly rugose, with an anterior shelf and a slight median depression deviding the sclerite into two low lateral bulges. Declivitous propodeal face transversely porcate above teeth, smooth and shining between and below them. Inferolateral propodeal margin with very broad smooth and shining areas between sparse carinae; opening of metapleural gland contained in a thin-walled cup like structure. Low rugosities on petiole and postpetiole(Fig. 4).

First gastric segment larger than other segments, mostly smoth and shining except for a short series of longitudinal carinae next to the postpetiolar junction. Gaster in lateral view ventrally convex and dorsally broadly convex. Tibiae and femora with longitudinal low rugosity; claws simple. Most of body plus extremities covered with abundant stiff,

erect to suberect, bristle-like hairs. Decumbent hairs on mandibles, scapes, funiculus. Abundant decumbent pilosity on pronotum and legs; also on anterior and anterolateral procoxal faces, mesocoxae and anterior mesocoxal face. Sparse decumbent pilosity on gaster. Body blackish brown, legs slightly lighter, wings (Fig. 3) brown. Worker, male and larvae unknown.

Ecology. - Practically unknown. The fact that the specimen was taken from a flight intercept trap on the ground would make it likely that this is a ground nesting species and not a canopy dwelling ant.

Discussion

The following characters from the generic diagnosis can be considered as plesiomorphic since they are common to the Myrmica group of genera, though to be close to the ancestral myrmicine stock:

1. 5, 6, 7, 9, 10, 11, 13, 18, 21. A median clypeal carina can be found in tetramoriines, myrmicines and throughout many ectatommines, the group of ponerines thought to be direct ancestors of Myrmicinae . The carinae on the clypeus are few and it is not hard to envisage a distinctly bicarinate state from the present condition. The position of the propodeal spiracle in Tetramorium and most myrmicine genus-group members is low on the side and towards the propodeal declivity, yet this is probably a derived state. The plesiomorphic state of situation of the propodeal spiracles is considered to be high and tending to midlength, or a little anterad of midlength(Bolton pers. comm.), a position quite similar to that in Bariamyrma .

The following can be considered apomorphic through reduction:

2. A higher palp formula count of 4,3 is predominant in myrmicines and tetramoriines, though the latter present occasional reductions of 3,2.

4. A broader clypeus such as that found in Myrmica Latreille , Tetramorium Mayr , Pheidole Westwood , etc. would be the primitive state.

20. Simple spurs, or their absence, is the apomorphic condition derived from pectinate spurs on the meso- and metatibiae, which is predominant in the Myrmica group.

The following are considered apomorphic through development:

3. The plesiomorphic state would be a straight to evenly shallowly convex anteromedian border with no prominences nor ornaments and not covering the basal mandibular margins, as is predominant in the Myrmica group and tetramoriines, with the exception of Rhoptromyrmex Mayr. There the clypeus is convex and covers the basal mandibular margins but it is not pronounced into a point (Bolton 1976: 295).

8. Frontal carinae are absent in the Myrmica group but developed in the tetramoriines. Other lower myrmicines with well defined frontal carinae are genera close to Lordomyrma Emery , yet these groups have gone on to develop scrobes, a character not evident in Bariamyrma .

14,15. The predominant and apparently primitive state in the Myrmica and Tetramorium groups is a long and narrow V-shaped open cleft that reaches between the metacoxae and slightly beyond, and the presence of a metasternal process (Bolton 1988: 268).

16. A subquadrate node is probably plesiomorphic in myrmicines. The low conical node is characteristic of most lower and higher pheidolines and can be encountered in Stenamma Westwood , Rogeria Emery , Messor Forel , Pheidole and others, including the Lordomyrma group of genera.

19. A strongly sclerotized and relatively slender sting with no flange development is considered plesiomorphic and is the condition in the Myrmica group. The tetramoriines present a similar flange as in Bariamyrma but it is preapical and the sting has not totally lost its piercing function (Kugler 1978:499). The sting of Bariamyrma suggests that it has lost the piercing capacity altogether and instead functions exclusively by airing some defensive secretion.

Bolton (1987:271) points out consistency of the position of the petiolar spiracle within narrow limits within genus groups, but the polarity of the states is difficult to assess due to the ways possible to reach that state.

The anterior wings have a closed radial cell, a primitive condition found in the Myrmica group, as opposed to an open cell, to be found in the tetramoriines and other groups: The loss of 1 cubital cell and of cross vein r-m is considered the derived state from 2 cells and the presence of the cross vein, as is the case with myrmicines, but lost in tetramoriines and other ants. The steps toward the loss of r-m have been documented by Bolton (1982: 339). In Bariamyrma Rs-M branches before r-2 but in Tetramorium it diverges at r-2 or apicad (Bolton 1976:372). The significance of hairs on the wings is unknown, though Kusnezov (1962: 378) noted their presence as variable amongst groups of ants.

The placement of this genus of apparently lower Myrmicinae into established tribes or genus groups at this moment is not clear. On account of its apomorphies it is obviously not a member of the Myrmica nor Tetramorium genera groups. If we consider the Pheidologeton group and the characters listed by Ettershank (1966: 115) as well as those pointed out by Bolton (1987: 265) there seems to be

no affinity. The lack of a clearly defined antennal club and presence of well developed frontal carinae in Bariamyrma plead against such a grouping. The only other universal characters within pheidologetines are the lack of a prominent median clypeal seta and a closed radial cell of the fore wing, but both are plesiomorphic states and of limited phylogenetic value. To place it in the Pheidolini or Myrmecini , polyphyletic assemblages of genera, would be of no heuristic value. The specimen does share a number of characters with Lordomyrma such as the mandibular structure, convex clypeus, frontal lobes, frontal carinae, antennae, and propodeal spiracles set well forward from the margin of the declivity. Yet in Lordomyrma the clypeus is clearly bicarinate, and distinct, albeit flat, antennal scrobes are formed. In this genus the petiolar peduncle tends to be shorter, the humeral angles somewhat sharper, tibial spurs are wanting, the sting presents no flange and the propodeal spiracle is below the base of the propodeal spine. Wheeler (1919: 105) illustrates the forewing of a male Lordomyrma and it is quite similar to Bariamyrma except for the anal vein, which does not extend beyond cu-a. Wheeler also notes the presence of hairy wings. A survey of the other genera related to Lordomyrma , such as Cyphoidris Weber , Lachnomyrmex Wheeler , Dacetinops Brown & Wilson , and Indomyrma Brown reveals distinct antennal scrobes and clubs, the lack of apical spurs on the meso- and metatibiae, and a raised, usually bicarinate, median clypeus. The sting in Lachnomyrmex tends to be flattened, and in Cyphoidris terminates in a narrow spatulate appendage. Lachnomyrmex has its propodeal spiracles set well back from the declivitous face margin, but Cyphoidris and Dacetinops have them positioned quite posterad. Accepting Bariamyrma as a member of this assortment of genera, and even though it has several apomorphies in relation to them, such as the reduced palpal segmentation and form of the sting, on the whole it seems that Bariamyrma is a somewhat primitive member of the group. Additional Bariamyrma material such as workers or larvae are needed, plus a detailed analysis of the Lordomyrma genus group , before relationships can be firmly established.

Etymology. - The generic name Baria is the name of a river next to the Cerro Neblina expedition basecamp. The species name is derived from the Latin diminutive for bristly, hispidula .