Strumigenys hemidisca

Identification
This species, the smallest member of the mandibularis series so far discovered, is apparently a member of the large and varied dacetine fauna inhabiting the epiphytes of the mountain rain forests of Colombia and Venezuela, scarcely known except through Plant Quarantine interceptions at U. S. ports of entry. Many species of this fauna remain undescribed, and quite a few of them possess significantly larger eyes than have their closest ground-living relatives. S. hemdiisca can be distinguished from all other species of Strumigenys known at present anywhere by the form of its propodeal lamellae.

Bolton (2000) - The structure of the lamella on the propodeal declivity is unique in the mandibularis-complex; all other species have either an upper or lower lobe or tooth, or both an upper and a lower lobe or tooth. This is the smallest species yet found in the complex.

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Venezuela.

Biology
Holotype and the two accompanying paratypes taken in U. S. Plant Quarantine from orchid plants originating at an unknown locality in Venezuela (E. Q. No. A-42465; USNM Lot No. 3720988), to be deposited in the U. S. National Museum; one paratype in the Museum of Comparative Zoology. The two paratypes are very similar to the holotype, scarcely differing in the usual measurements by more than the expected errors. One specimen has the gaster a bit lighter and more reddish in color than the holotype, and there is very slight variation in the degree of convexity of the propodeal lamellae.

Nomenclature

 *  hemidisca. Strumigenys hemidisca Brown, 1953f: 107 (w.) VENEZUELA. See also: Bolton, 2000: 535.

Description
Holotype worker: TL 2.78, HL 0.60, ML 0.39, WL 0.64 mm.; CI 82, MI 65. Closely similar to S. smithii, but smaller and with slightly longer mandibles relative to head size, also the following differences: 1. Preapical teeth of mandible farther apart and farther from the apical teeth; distal preapical tooth distant from the apical fork by about its own length, slightly longer than the proximal tooth; the latter situated at or very near the midlength of the mandible. 2. Eyes a little larger and more convex. 3. Alitrunk slightly more strongly depressed; propodeal dorsum virtually continuous with the very gradually sloping declivity. 4. Propodeal lamellas modified into the form of low, nearly perfectly semicircular discs, only very feebly approaching straightness along one small portion of the generally rounded free edge and without traces of either upper or lower angles or teeth. These discs are feebly convex over their mesial and lateral surfaces and are densely punctate, continuing the sculpture of the adjacent lateral surfaces of the alitrunk. 5. Petiole and postpetiole as in smithii, disc of the latter very slightly more convex, shining, with a few very fine, short costulae along the anterior border. Posterodorsal spongiform collar of petiolar node not so well developed. 6. Gastric basal costule vestigial, fewer than in smithii and not half so long, scarcely longer than the distances separating them. 7. Ground hairs of head slightly more conspicuous, but this may be due to darker integumental background color. Sparse appressed fine hairs of gastric dorsum extremely small and inconspicuous. 8. Color deep ferrugineous; gaster blackish-mahogany; mandibles and appendages lighter and more yellowish.

Bolton (2000) - TL 2.5-2.7, HL 0.58-0.62, HW 0.46-0.50, CI 79-82, ML 0.36-0.39, MI 60-65, SL 0.42-0.44, SI 88-91, PW 0.31-0.34, AL 0.62-0.64 (3 measured).

Characters of mandibularis-complex. Proximal preapical tooth at or just proximal of midlength of inner mandibular margin. Length of proximal preapical tooth less than distance separating it from distal preapical tooth. Outer margins of mandibles very shallowly convex at full closure. Disc of postpetiole broader than long, mostly smooth but with some peripheral sculpture. Propodeal declivity with a continuous rounded lamella, without trace of teeth or lobes at either apex or base of lamella. First gastral tergite with slender hairs basally.

Type Material
Bolton (2000) - Holotype and paratype workers, VENEZUELA: loc. unknown; intercepted by U. S. Plant Quarantine, from orchids, E.Q. No. A-42465, USNM Lot No. 37-20988 [examined].