Cyphomyrmex

Snelling, R. R. & Longino, J. T., 1992, Revisionary notes on the fungus-growing ants of the genus Cyphomyrmex, rimosus-group (Hymenoptera: Formicidae: Attini)., Insects of Panama and Mesoamerica: selected studies., Oxford: Oxford University Press, pp. 479-494 : 479-484

Cyphomyrmex Mayr, 1862,

is a genus of fungus-growing ants belonging to the exclusively New World tribe Attini. Among the dozen genera presently recognized within the Attini, Cyphomyrmex is one of the most distinctive. The body is dull and, for the most part, without obvious sculpture, although a few obscure rugules may be present on the mesosoma. The first gastral tergum is without tubercles. Pilosity, except for a few erect simple hairs on the mandibular region of the head, is usually closely appressed to the body surface and is scale-like in appearance; in a few species the pilosity is suberect, but then it is also broad and squamiform. The frontal lobes of the head are exceptionally broad, completely concealing the antennal sockets, and the head is usually widest across the frontal lobes. Mesosomal spines are replaced in most species by low, blunt tubercles; in a few species even these are absent or nearly so.

The biology of Cyphomyrmex is not very well known, even though some species are among the mostly commonly encountered terrestrial species. The ants themselves are small, of drab coloration, slow-moving, and often become immobile when disturbed, sometimes for several minutes. When an ant feigns death the appendages are drawn close to the body and the ant then seems to be nothing more than a small particle of soil or other debris.

Colonies are small, probably not exceeding 500 workers and usually far fewer; numerous dealate females are often present within a colony but they apparently are non-reproductive. The colonies are commonly situated in soil or rotting wood on the ground, or distributed within leaf-litter. They may also be located in dead, decaying tree limbs, in matts of moss on tree trunks, or within epiphytic pseudobulbs.

The fungus gardens of Cyphomyrmex are grown on insect faeces and other bits of debris collected by the foraging workers. They do not at all resemble the large spongiform fungus gardens of Atta , Acromyrmex , and some other genera. Instead, the fungus consists of cheese-like bodies up to 0.5 mm in diameter. These bodies, or bromatia, are placed directly on the excrement from which they derive nutriment. Two species in the rimosus group grow a basidiomycete fungus belonging to the Agaricaceae, but the remaining species, as far as is currently known, cultivate bromatia that form solid, polygonal masses of an unidentified yeast-like fungus; Wheeler (1907) named one such fungus Tyridiomycesformicarum. However, until these fungi can be cultured to maturity, their identities and affinities remain unresolved.

The genus is largely neotropical in distribution and its constituent species were reviewed by Kempf (1964, 1966). In these two papers, Kempf recognized a minimum of 31 species placed in two species groups: the strigatus group (15 species) and the rimosus group (16 species). One more species was added to the rimosus group by Kempf (1968).

The present study is limited to species in the rimosus group and particularly the rimosus complex. Kempf (1966) left unresolved the status of 16 infraspecific forms assigned to C. rimosus , noting that this ' ... is both the commonest form in the genus and at the same time a residue of classification. The puzzling variability of the complex, which gave rise to a number of infraspecific names in the past, needs a special study

We intend only to amplify and continue the exemplary work of the late Dr Kempf: one adventive species has been discovered in the United States; new synonymy is proposed; four new species are described; and several infraspecific forms assigned to C. rimosus are elevated to specific rank.

Collections

Material used in this study is from the following collections: British Museum (Natural History) (BMNH); Museo de Instituto di Zoologia Sistematica, Universita di Torino (MIZS); Museum of Comparative Zoology, Harvard University (MCZ); Museum d'Histoire Naturelle, Geneva (MHNG); Museum National d'Histoire Naturelle, Paris (MNHN); Natural History Museum of Los Angeles County (LACM); United States National Museum of Natural History (USNM); and the personal collections of the junior author (LONG), J.C. Trager OCT), and G.J. Umphrey (UMPH).

Terminology

In general, the descriptive mode follows that of Kempf; 1964, 1966; in order to facilitate comparison with his descriptions. The morphological terminology is conventional and follows Kempf, except that we prefer 'propodeum' to 'epinotum'. The symbol' [[worker]]' is used for worker and '[[queen]] ' is used for female or queen.

Head width is measured between the outer margins of the head, in full frontal view, at the upper margin of the eyes and does not include the supraocular tubercle when it is present. Head length is the maximum measurable length between the lower clypeal margin and the apex of the occipital corner, lobe, or spine, as appropriate. The interocular distance is the minimum distance between the inner margins of the compound eyes. The eye length is the maximum diameter of the eye as seen in lateral view and the oculomandibular distance is the minimum distance between the lower eye margin and the mandible base.

In the descriptions of new species, measurements for the holotype are followed, in parentheses, by those for the remaining specimens in the type series.

SYSTEMATICS

In his two papers reviewing the species of Cyphomyrmex , Kempf (1964, 1966) divided the genus into two species groups, the sirigosus group and the rimosus group. The subgenus Cyphomannia Weber, 1938 (type-species Cyphomyrmex laevigatus Weber , 1938) was treated as a synonym of Cyphomyrmex because its type-species was included in the rimosus group, to which the generitype also belongs. Although Weber '1966 attempted to reinstate Cyphomannia , we (ind his conclusions less compelling that those of Kempf (1964, 1968).

Kempf (1964) deflned the two species groups as follows:

I. Group of rimosus : Preocular carina curving mesally above eves, not joining up with the postocular carina, which extends from the occipital corner to posterior or inferior border of eye this character is not well-expressed in longiscapus and allies, which resemble the strigatus group in this respect); mandibles with 5 teeth only; two or no median pronotal tubercles present.

Six subgroups are recognized here: kirbyi , costatus , foxi , rimosus , salvini , and laevigatus .

II. Group of strigatus : Preocular carina extending all the way back to the occipital corner, forming the inferior border of the antennal scrobe; mandibles with 7 or more teeth, gradually diminishing in size towards base; a single median pronotal tubercle usually well developed in the worker caste.

The following key will serve to separate workers of the members of the rimosus group that we recognize. It is based, in part, on the key by Kempf (1966). The species treatments following the key omit C. costatus Mann , C. wheeleri Forel ( costatus subgroup), C. kirbyi Mayr , C. transversus Emery , and C. bicornis Forel ; all were adequately covered by Kempf (1966) and we have no new data to present.

Key to species of rimosus group workers

1 Preocular carina not curved mesally in front of eye; posterolateral limit of scrobe marked by a difference in sculpture and usually without posterior carina (Fig. 30.34), except C. wheeleri (Fig. 30.36) 2

- Preocular carina curved mesally in front of eye; posterolateral limit of scrobe marked by another carina arising from occipital corner and extending to border of eye, but never confluent with preocular carina (Fig. 30.35) 4

2(1) Antennal scape not surpassing occipital corner in repose; lateral pronotal tubercles prominent; posterior genal carina present 3

- Antennal scape surpassing occipital corner in repose; lateral pronotal tubercles absent; posterior genal carina absent below longiscapus Weber

3(2) Disc of first gastral tergum with strong longitudinal ridge on each side of middle; midpronotal tubercles absent; postero-dorsal margin of petiole neither drawn out nor bidentate costatus Mann

- Disc of first gastral tergum without costa on either side of middle; mid-pronotal tubercles present; postero-dorsal margin of petiole drawn out as foliaceous bidentate lamina wheeleri Forel

4(1) Antennal scape not surpassing strongly auriculate occipital corner (Fig. 30.4); pronotum without tubercles (Fig. 30.29) 5

- Antennal scapes usually surpassing occipital corner (Figs 30.1-30.3, 30.5-30.9); if latter are prolonged, at least lateral pronotal tubercles are present (Fig. 30.30) 6

5(4) Anterior mesonotal tubercles conical, posterior tubercles low and tumuliform; petiole node much less than three times wider than long bicornis Forel

- Mesosoma completely unarmed, dorsal profile evenly rounded (Fig. 30.29); petiole node about three times broader than long laevigatus Weber

6(4) Mid-pronotal tubercle pair absent 7

- Mid-pronotal tubercle pair present 11

7(6) Metafemur dilated and ventrally carinate at basal one-third (Fig. 30.23); funicular segments 2-8 about as long as broad 8

- Metafemur not dilated and ventrally carinate at basal one-third (Figs 30.26, 30.27 funicular segments 2-8 distinctly longer than broad 9

8(7) Propodeum dentate with basal face laterally marginate to carinate (Fig. 30.31); apex of scape scarcely surpassing tip of occipital corner flavidus Pergande

- Propodeum edentate and basal face rounded, neither marginate nor carinate laterally -'Fig, 30.32); apex of scape surpassing occipital corner by more than its greatest thickness peltatus Kempf

9(7) Occipital corner low and obtuse, not spine-like (Fig. 30.7); anterior mesonotal tubercles low and obtuse (Fig. 30.15) 10

- Occipital corner prominent and spine-like (Fig. 30.2); anterior mesonotal tubercles prominent, acute and distinctly longer than wide at base (Fig. 30.30) cornutus Kempf

10(9) Anterior clypeal margin distinctly emarginate in middle; parafrontal tooth conspicuous (Fig. 30.7); propodeum not angulate in profile (Fig. 30.15) nesiotus , new species

- Clypeal margin straight; parafrontal tooth weak; propodeum angulate in profile (Fig. 30.12) kirbyi Mayr

11(6) Maximum expansion of frontal carinae less than, or equal to, distance between eyes (Fig. 30.8); mesosoma finely but distinctly rugose lateral pronotal and anterior mesonotal tubercles long and spine-like) 12

- Maximum expansion of frontal carinae conspicuously greater than distance between eyes (Figs 50.1-30.7); mesosoma granulose, without rugae 13

12(11) Expanse of frontal carinae less than interocular distance; propodeum with pair of longitudinal submedian carinae; dorsal lobes of post-petiole strongly raised and subspiniform foxi Andre

- Expanse of frontal carinae at least equal to interocular distance; propodeum without longitudinal submedian carinae; dorsal lobes of post-petiole low and rounded podargus , new species

13(11) Occipital corners, in frontal view, elevated as a broad lobe (Figs 30.1, 30.5) or distinctly spine-like; anterior mesonotai tubercles high, usually conical 14

- Occipital corners, in frontal view, low and subangulate, neither elevated nor spine-like (Figs 30.6, 30.9); anterior mesonotai tubercles usually low and tumuliform 17

14(13) Occipital corner produced as spine-like process (Fig. 30.1) and frontal carina not reaching base of process; anterior mesonotai tubercle high, conical 15

- Occipital corner produced as broad lobe, frontal carina extending to top of lobe to join posterior carina (Fig. 30.5); anterior mesonotai tubercle high but obtuse (Fig. 30.13) major Forel

15(14) Basal longitudinal groove of first gastral tergum distinct; posterior mesonotai tubercles conical; appressed and subappressed hairs of first gastral tergum broad and scale-like 16

- Basal longitudinal groove of first gastral tergum weak or absent; posterior mesonotal tubercles low, not tooth-like; hairs of first gastral tergum slender or broad, all appressed vorticis Weber

16(15) Occipital spine higher than broad at base; propodeum without sharply defined lateral ridges and without tooth on declivity; posterior mesonotal tubercle lower and more obtuse than anterior tubercle salvini Forel

- Occipital spine broader at base than high; propodeum with sharply defined lateral carinae terminating on declivity as a triangular tooth (Fig. 30.10); posterior mesonotal tubercle nearly as high and acute as anterior tooth bicarinatus new species

17(13) Node of petiole less than three times as broad as long; disc of node of post-petiole with median impression shallow and ill-defined; body hairs usually fine 18

- Node of petiole three times as broad as long; disc of node of post-petiole broad and deeply impressed; body hairs thickly squamosa transversus Emery

18(17) Hairs on head and gaster appressed and scaliform, mesosomal tubercles usually low and tumuliform, but if subacute or dentiform, propodeum is bispinose 19

- Hairs on head and first gastral tergum recurved or hook-like, neither appressed nor scaliform; thoracic tubercles sharply pointed and propodeum without spines hamulatus Weber

19(18) Declivitous face of propodeum slightly angulate or with pair of broad, tooth-like protuberances (Figs 30.14, 30.1 7) 20

- Declivitous face of propodeum with pair of definitely spiniform processes fFig. 30.1 1 dixus , new species

20 (19) Small species, head width 0.56 mm or less; hairs in centre of first gastral tergum closely appressed and mostly separated by more than their own lengths; median basal groove of first gastral tergum short and usually indistinct (Fig. 30.22) minutus Mayr

- Larger species, head width more than 0.62 mm; hairs in centre of first gastral tergum coarse, not fully appressed, and mostly separated by less than their own lengths; basal groove of first gastral tergum distinct and more than twice as long as wide (Fig. 30.21) rimosus (Spinola)