Strumigenys mutica group

Strumigenys mutica group Bolton (2000)

Malagasy

 * Strumigenys erynnes
 * Strumigenys tathula

Malesian-Oriental-East Palaeartic

 * Strumigenys media
 * Strumigenys mutica
 * Strumigenys takasago
 * Strumigenys yaleogyna

Worker Diagnosis
The group is diagnosed, with slight differences, for two different regions:

Malagasy
Mandibles in full-face view and at full closure elongate-triangular; teeth occupy only the apical half of each mandible but the opposing rows fully engage. Basal halves edentate and with a large space present between the mandible blades, through which the labral lobes are visible. In ventral view outer margin of mandible without an inflected prebasal angle. MI 20-30.

Dentition. With 12 very crowded teeth and denticles that occupy the apical half to third of the exposed length of the mandible. The basal tooth is followed by 10 denticles of similar size and an enlarged apical tooth. A long, shallowly concave diastema is present between basal tooth and basal lamella.

Basal lamella of mandible a high rounded lobe that is partially or mostly visible in full-face view with the mandibles fully closed.

Labrum terminates in a pair of triangular, digitate or conical narrow lobes.

Clypeus with anterior margin broadly convex, the outer margins of the mandibles intersecting the clypeal margin close to the anterolateral angles at full closure.

Clypeal dorsum with appressed narrowly spatulate hairs, the clypeal margins fringed with similar but slightly elevated narrowly spatulate curved hairs that are directed anteriorly.

Preocular carina conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible weakly or not developed, the side tending to round into the ventre. Postbuccal impression very shallow.

Cuticle of side of head within scrobe reticulate to reticulate-punctate.

Scape moderate, SI 76-88 (in Malagasy species), subcylindrical to weakly dorsoventrally flattened in section.

Leading edge of scape with a row of narrowly spatulate hairs that are directed toward the apex of the scape. (In one extralimital species basally directed hairs occur.)

Alitrunk compact, short and high in profile and the dorsal outline distinctly biconvex, with a promesonotal convexity and a propodeal convexity, the two separated by a distinctly impressed metanotal groove.

Pronotum without a median longitudinal carina.

Propodeum unarmed or bidentate, the dorsum rounding broadly into the declivity, the latter with a narrow lamella that extends the depth of each side.

Spongiform appendages of waist segments present but reduced to inconspicuous small lateral lobes and thin posterior collars. Base of first gastral sternite in profile without a pad of dense spongiform tissue.

Pilosity. Apicoscrobal hair and pronotal humeral hair absent. Standing hairs absent to sparse on dorsal surfaces of head and alitrunk; when present with at most one pair behind highest point of vertex, and another pair on the mesonotum. Dorsal (outer) surfaces of middle and hind tibiae with apically curved small spatulate hairs that are subappressed to appressed; without elongate freely projecting hairs.

Sculpture. Dorsum of head behind clypeus finely densely reticulate-punctate everywhere; alitrunk similarly sculptured or with smooth patches on pleurae.

Malesian-Oriental-East Palaeartic
Mandibles in full-face view and at full closure elongate-triangular; teeth occupy only the apical half of each mandible but the opposing rows fully engage. Basal halves edentate and with a large space present between the mandibles, through which the labral lobes are visible. In ventral view outer margin of mandible without an inflected prebasal angle. MI 20-29.

Dentition. Consists of 12 very crowded teeth and denticles that occupy the apical half to third of the exposed length of the mandible. The basal tooth is followed by 10 denticles of similar size and an enlarged apical tooth. A long, shallowly concave diastema is present between basal tooth and basal lamella.

Basal lamella of mandible a high rounded lobe that is partially or mostly visible in full-face view with the mandibles fully closed.

Labrum terminates in a pair of narrow triangular, digitate or conical lobes.

Clypeus with anterior margin broadly convex, the outer margins of the mandibles intersect the clypeal margin close to the anterolateral angles at full closure.

Clypeal dorsum with appressed narrowly spatulate hairs, the clypeal margins fringed with similar but slightly elevated narrowly spatulate curved hairs that are directed anteriorly.

Preocular carina conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible weakly or not developed, the side tending to round into the ventre. Postbuccal impression very shallow.

Cuticle of side of head within scrobe reticulate to reticulate-punctate.

Scape short to moderate, SI 63-76, subcylindrical to weakly dorsoventrally flattened in section.

Leading edge of scape with a row of narrowly spatulate hairs that are usually all directed toward the apex of the scape; in one species some basally directed hairs occur.

Alitrunk compact, short and high in profile and the dorsal outline distinctly biconvex, with a promesonotal convexity and a propodeal convexity, the two separated by a distinctly impressed metanotal groove.

Pronotum without a median longitudinal carina.

Propodeum usually unarmed, the dorsum rounding broadly into the declivity, only rarely with teeth. Declivity with a narrow lamella that runs its height on each side.

Spongiform appendages of waist segments present but reduced to inconspicuous small lateral lobes and thin posterior collars. Base of first gastral sternite in profile without a pad of dense spongiform tissue.

Pilosity. Pronotal humeral hair absent. Apicoscrobal hair absent. Standing hairs absent to sparse on dorsal surfaces of head and alitrunk; when present with at most one pair behind highest point of vertex and another pair on the mesonotum. Dorsal (outer) surfaces of middle and hind tibiae with apically curved small spatulate hairs that are subappressed to appressed; without elongate freely projecting hairs.

Sculpture. Cephalic dorsum behind clypeus finely densely reticulate-punctate everywhere; alitrunk similarly sculptured or with smooth patches on pleurae.

Malagasy
Of the six species currently in the mutica-group two, Strumigenys erynnes and Strumigenys tathula, occur in Magadascar. Of the other four, two are from New Guinea (Strumigenys media, Strumigenys yaleogyna), one is known only from Taiwan (Strumigenys takasago) and the other, Strumigenys mutica itself, is widely distributed from Japan to Java. The group remains unknown from the West Palaearctic and Afrotropical regions and is absent from the New World. The characters of the diagnosis will immediately isolate erynnes and tathula from all their congeners in both Africa and Madagascar.

Malesian-Oriental-East Palaeartic
A widely distributed group of which six species are currently known: two from New Guinea, one widely distributed from Japan to Java, one from Taiwan and two from Madagascar; more undoubtedly await discovery.

Members of the group constituted the former genus Kyidris, now abandoned (Bolton, 1999). The distinctive form of the mandibles (see also under gyges-group), coupled with the compact biconvex alitrunk, are immediately diagnostic; femora in the group tend to be longer than elsewhere in the genus. The New Guinean species (Strumigenys media and Strumigenys yaleogyna) are always found in a post-xenobiotic association with Strumigenys loriae, described by Wilson & Brown (1956) and Holldobler & Wilson (1990). Two species, Strumigenys mutica and the Malagasy Strumigenys erynnes occur freely in the leaf litter and topsoil. No details of the biology of Strumigenys takasago have been recorded.