Cyphomyrmex wheeleri Forel

Kempf, W. W., 1966, A revision of the Neotropical fungus-growing ants of the genus Cyphomyrmex Mayr. Part II. Group of rimosus (Spinola) (Hym. Formicidae)., Studia Entomologica (N. S.) 8, pp. 161-200: 167-172

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Cyphomyrmex wheeleri Forel


2. Cyphomyrmex wheeleri Forel   HNS  

(Figs. 7, 25, 37, 49)

Cyphomyrmex wheeleri Forel   HNS   , 1900: 282-4 (Worker, female: U.S.A., Texas: Austin). Wheeler, 1907: 725-6, 765-8, fig. 30, pl. 49 fig. 2 (Worker, female, male; U.S.A., Texas: Austin, Belton, Langtry, Fort Davis; California: Three Rivers; Bion.). - Weber, 1940: 409 (Worker; key). - Creighton, 1950: 315-7, pl. 40, figs. 1-4 (Worker, female, male; distrtb., key). - M.R. Smith in Muesebeck et al, 1951: 830 (U.S.A.: Texas, California; Mexico).

Types. - Workers and a female collected by W. M. Wheeler in the environs of Austin, Texas, U.S.A.; three syntype or nidotype workers, received on exchange from the Museum of Comparative Zoology at Harvard College for my collection (WWK), were examined.

Worker. - Total length 2.8-3.4 mm; head length 0.71- 0.85 mm; head width 0.62-0.72 mm; thorax length 0.83-1.06 mm; hind femur length 0.64-0.78 mm. Light yellowish-brown; older specimens also darker. Integument, very sharply reticulatepunctate, opaque. Mandibles and funiculi more superficially sculptured and somewhat shining.

Head as shown in Fig. 7. Anterior apron of clypeus flattened, only vestigially notched on convex anterior border; lateral teeth, next to origin of frontal lobes, small and almost hidden by the latter. Frontal lobes elongate-rounded and flat, covering cheeks in full-face view. Frontal carinae moderately diverging caudad, straight. Occipital corners lobate, prominent, longitudinally carinate. Paired carinae on vertex feeble, short, scarcely diverging cephalad. Preocular carina fading out above eyes, not curving mesad. Postocular carina extending foreward from lateral face of occipital lobe, becoming obsolete just in front of posterior orbit of eyes, closing completely the antennal scrobe. Supraocular tumulus dentiform, situated below the postocular carina. Inferior border of sides of head carinate on posterior half. Eyes with 8-10 facets across greatest diameter. Scape strikingly attenuate at base, strongly incrassate apicad, not projecting beyond antennal scrobe. Funicular segments III-IX about as broad as long, I and X longer than broad.

Thorax as shown in Fig. 25. Pronotum with a pair of small denticles on disc, the latter laterally marginate between the marked humeral angle and the strong lateral pronotal tooth; antero-inferior corner acutely dentate. Mesonotum forming a shallowly impressed oval disc, the borders of which are flanked by the pair of anterior and posterior carinate welts; the anterior pair separated from the posterior pair by a small impression. Mesoepinotal suture distinct on bottom of broadly and deeply impressed mesoepinotal groove. Basal face of epinotum transversely shallowly concave, sides somewhat diverging caudad, bordered by carinae, which become foliaceous in front of the compressed, lamellate, acute, epinotal tooth; infradental lamellae low, bordering the upper half of the declivous face. Epinotal spiracle small, situated on the vestigial oblique carinule. Femora, especially hind femora, postero-ventrally crested and bearing on basal first a broader foliaceous lobe (Fig. 49). Tibiae subprismatic.

Pedicel as shown in Figs. 25 and 37. Petiolar node trapezoidal in dorsal view, broadest just behind the obliquely truncate anterior corners, its dorsum flattened, oblique; posterior corners with a raised, strong tooth; posterior border likewise raised and lamelliforns connecting the teeth from base to tip. Postpetiole decidedly broader than long, its dorsum with a shallow median impression between a pair of low, longitudinal welts, the extremities of which are tumuliform. Posterior border moderately and evenly rounded. Gaster anteriorly truncate; tergum I with a short antero-median impression, its sides submarginate.

Pilosity scarce, inconspicuous, decumbent throughout; dorsum of head and gaster with small, whitish, scale-like hairs.

Female. - Described both by Forel (1900) and Wheeler (1907) and pictured by Creighton (1950). Differs from costatus   HNS   in larger size, reticulate-punctate body sculpture, presence of paired erect teeth on petiole and absence of two pairs of longitudinal carinae on tergum I of gaster.

Male. - Described by Wheeler (1907) and pictured by Creighton (1950). No specimen seen.

Distribution. - The entire range of wheeleri   HNS   seems to lie outside of the Neotropical region. So far, it has been reported from central and southwestern Texas and southern California in the U.S.A., and from Mexico (Smith, 1951).

Specimens examined: 6 workers, as follows:

U.S.A., State of Texas: Austin, W: M. Wheeler leg. 3 workers (syntypes); Fisher Hill, Davis Mts., July 26, 1955, A. C. Cole leg. 3 workers (WWK).

Discussion. - The variability of wheeleri   HNS   , according to the limited material available for this study, seems to be very little and finds its expression chiefly in size and color. The syntype specimens from Austin belong to the lower range of the measurements, whereas the three workers from the Davis Mts. are considerably larger and partly darker in color.

C. wheeleri   HNS   is closest to costatus   HNS   . Following are the main differences for the worker caste: Larger size (cf. measurements); body very sharply reticulate-punctate throughout; anterior clypeal border scarcely notched; carinae on vertex weak; postocular carina sharp, the supraocular tubercle lying below the carina; eyes larger with more facets; midpronotal denticles present; antero-inferior pronotal and epinotal teeth acute; petiole with a pair of postero-dorsal teeth; tergum I of gaster without four strongly raised longitudinal costae.

Bionomics. - C. wheeleri   HNS   is more xerophilous than most species of the genus. According to Wheeler (1907: 765-8), whose field studies were made in the vicinity of Austin, it occurs only in arid regions. Nests were found principally on the higher and drier terraces of limestone hills, although a few nests were also discovered in the hard, pebbly soil of open wood at lower altitudes.

The hillside nests are invariably under large stones, which cover both horizontal and vertical galleries (the latter descending into the ground to a depth of 10-15 cm). One of the horizontal galleries communicates with the exterior at the edge of the stone. The entrance is sometimes marked by a small crater. The sessile fungus garden, having the size of pecan nut, is found at a particular widened portion of either the horizontal or the vertical galleries. The garden presents a. flocculent appearance, and consists of small slivers of vegetable debris (probably entire sections of stems of herbaceous plants) bound together by the snow white mycelium. Skeletal parts of dead insects, principally fragments of coleopterous elytra, have been found inside the garden; they were probably added to the structure in order to give it consistency. The ants attach the refuse as a flat mass to the undersurface of the stone, or more rarely dump it outside the entrance.

The woodland nests were marked by craters of earth crumbs, around a small, circular opening of a vertical gallery, descending to appreciable depth into the soil. Wheeler was unable to unearth the fungus garden.

The colonies usually do not comprise more than a few dozen workers with a single queen. Their activity seems to be mainly nocturnal. Sexual forms appear in the nests ready for nuptial flight from early to late in June. As all other species of the present genus, the worker move slowly and "feign death" at the least disturbance.