Strumigenys morisitai group

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Strumigenys morisitai group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Worker Diagnosis

Mandibles in full-face view and at full closure elongate and bizarre, divided into radically differently shaped proximal and distal portions, the latter accounting for about the apical third of the total length. Proximal portion of mandible: narrow basally, expanding apically into a club-like shape; inner margins are edentate and shallowly convex, separated basally and enclose a small triangular gap between themselves and the clypeal margin. Distal of the basal gap the inner margins meet and run parallel before diverging again close to their apices. Distal portion of mandible: projects downwards anteroventrally from the club-shaped proximal portion; narrow and forceps-like, with the outer margin shallowly convex and with an edentate gap between them. Distal of the gap the apices of the mandibles have a few minute teeth whose apices do not quite meet; terminally the extreme apices of the mandibles engage. In profile the mandible is downcurved almost at a right-angle at about its midlength, the point where proximal and distal specialised portions meet. MI 30-33.

Dentition. See above.

Basal lamella not visible (mandibles fully closed).

Labrum terminates in a pair of elongate narrow lobes.

Clypeus with anterior margin narrowly rounded, continuous with the sides; outer margins of the fully-closed mandibles flank the lateral clypeal margins in full-face view. In ventral view lateral margins of clypeus do not extend beyond outer margins of mandibles.

Clypeal dorsum with numerous anteriorly directed small appressed spatulate hairs. Lateral margins of clypeus without projecting hairs.

Preocular carina conspicuous in full-face view.

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

Scape subcylindrical, shallowly curved near base, SI 61-69.

Leading edge of scape with a row of narrowly spatulate hairs that curve toward the apex of the scape.

Pronotal dorsum not marginate, without a median carina.

Propodeum with a pair of small triangular teeth, subtended by an approximately straight lamella that is not expanded into propodeal lobes ventrally.

Spongiform appendages of waist segments large, well developed. Base of first gastral sternite in profile with a narrow arcuate crest of spongiform tissue.

Pilosity. Pronotal humeral hair absent. Apicoscrobal hair present, flagellate. Subappressed narrowly spatulate curved hairs numerous on head and dorsal alitrunk. Hairs on first gastral tergite also narrowly spatulate but longer and mostly strongly arched toward the midline.

Notes

Even in a genus such as Pyramica, where peculiarly shaped mandibles are commonplace, the utterly bizarre structure encountered in Strumigenys morisitai still promotes a sense of wonder. The shape evolved here is unique and its purpose impossible to determine. The relatively broad club-shaped basal portions of the mandibles contrast very strongly with the much narrower forceps-like apical portions, and these project down from the basal portions at a marked angle. Teeth are very small and restricted to the extreme apex, which is the only place on the apical portion where both blades fully engage. The relationships of a species as specialised as this are very difficult to determine, but the structure of the head generally, and of the clypeus and scape in particular, is very reminiscent of the baudueri group, which may represent the place of origin of morisitai.

References

  • Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.