Strumigenys solifontis

Nests are found under stones or in cavities of stones in woodland margins. Colonies are usually polygynous comprising over 200 workers (Masuko, 1980; Japanese Ant Image Database).

Identification
Dong & Kim (2020) = This species can be distinguished from other Korean Strumigenys species by the combination of the following characteristics:
 * Apicoscrobal hair present, short, not flagelliform.
 * Mandibles linear, teeth apically.
 * Body slender and thin.
 * Pronotal humeral hair long.
 * Mesosoma with long filiform hairs.
 * Propodeal lamellae slightly concave anteriorly.

The propodeal lamella of all Korean specimens examined is not evenly distinctly concave compared with Japanese (JAID 2006: PCD1050-11, PCD2228-53) and Taiwanese specimens (ANT-WEB, CASENT0280743), including for the picture of the type specimen available on JAID.

Bolton (2000) - A member of the smythiesii complex in the Strumigenys godeffroyi-group. There are four species known in the smythiesii-complex in which the specialised humeral hair is stiff and simple, moderately long, straight or at most only evenly shallowly curved; definitely not flagellate: Strumigenys hispida, Strumigenys jepsoni, Strumigenys liukueiensis, solifontis. Of these liukueiensis is easily distinguished as it is much more densely hairy than the other three. Its upper scrobe margin has freely projecting straight hairs anterior to the apicoscrobal hair, the dorsal alitrunk has more than four pairs of erect hairs and the hind basitarsus has at least 5 stiffly erect hairs on its dorsal (outer) surface. The other three species lack freely projecting straight hairs anterior to the apicoscrobal hair, the dorsal alitrunk has at most four pairs of erect hairs and the hind basitarsus has only 1-2 erect hairs, that are fine and flagellate, on its dorsal (outer) surface.

The Fijian jepsoni lacks laterally projecting hairs on the cephalic dorsolateral margin posterior to the apicoscrobal hair. The propodeal dorsum and petiole node dorsally are smooth and shining and the dorsal surface of the petiolar peduncle has a narrow cuticular carina on each side. In profile the carina arises anterior to the spiracle, extends to the node and ascends its anterior face. In dorsal view the carinae are straight to near the base of the node where they are concave and have a pinched-in appearence. In both hispida and solifontis 2-4 conspicuous laterally projecting hairs occur on the dorsolateral margin of the occipital lobe, posterior to the apicoscrobal hair. The propodeal dorsum and petiole node dorsally are reticulate-punctate and the dorsal surface of the petiolar peduncle lacks the cuticular carinae as seen in jepsoni.

S. hispida (CI 72-73, SI 85-86) has a broader head and shorter scapes than solifontis (CI 66-69, SI 98-100). S. hispida also has the transverse row of hairs near the base of the first gastral tergite flagellate. Posterior to this the tergite is hairless except for a transverse row at the apex of the sclerite. In solifontis hairs in the transverse row near the base of the first gastral tergite are stiff and simple, and other hairs arise from the sclerite between this row and the apical transverse row. Finally, in hispida the lamella on the propodeal declivity, in absolute profile, is about equally broad throughout and has its posterior (free) margin nearly straight, at most only extremely feebly convex. In solifontis the lamella in absolute profile becomes broader basally and its posterior (free) margin is markedly convex in at least its lower half.

Distribution
Rather rare in Honshu, but common on Okinawa Island, Japan (Japanese Ant Image Database).

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan. Palaearctic Region: Japan, Republic of Korea.

Biology
The hunting behaviour of S. solifontis was investigated by Masuko (1984). See Hunting Tactics in Short-Mandibulate Strumigenys for more about this ant's hunting behavior.

Chien and Lin (2015) analyzed the chemical constituents of the venom of five Taiwanese Strumigenys species: Strumigenys chuchihensis, Strumigenys formosensis, Strumigenys liukueiensis, Strumigenys minutula and Strumigenys solifontis for a chemotaxonomy study. The venom was collected from extruded stings and was thought likely to contain a mixture of poison (venom) and Dufour gland secretions. GC/MS profiles showed that three of the five species were clearly differentiated by the chemical composition of their sting secretions. Two remaining two species, S. chuchihensis and S. liukueiensis, showed chemical signatures that were not significantly different from one another.

Nomenclature

 *  solifontis. Strumigenys (Strumigenys) solifontis Brown, 1949d: 18 (w.q.) JAPAN. See also: Bolton, 2000: 813.

Worker
Holotype. Differs from the closely related Strumigenys lewisi as follows:

(1) TL 3.15 mm. (Paratypes, 2.93-3.33 mm.)

(2) Head both relatively (CI 69) and absolutely (HL 0.74 mm.) longer than in lewisi, also slightly less convex above and generally more dorsoventrally depressed (ICD 44). Eyes less convex. The paratypes are as follows for the same measurements and proportions: HL 0.71-0.80 mm., CI 66-69, ICD 41-43.

(3) Mandibles both absolutely and· relatively (ML 0.39 mm.; MI 53) longer than in lewisi, and relatively slightly more robust. The preapical tooth is long and acute, set its length or slightly more away from the dorsal apical tooth (slightly less in lewisi). Apical fork much like that of lewisi (dorsal tooth long and acute, ventral shorter and more blunt at apex; between, on the dorsal margin of ventral tooth near its base, two short denticles). Paratypes: ML 0.37-0.41 mm., MI 51-52.

(4) Thorax very slender, with dorsal profile from lateral view broadly and rather strongly concave from the summit of the convexly raised promesonotum to the propodeal teeth, much more strongly concave than in lewisi.

(5) Pilosity similar to that of lewisi, but the dorsal hairs a little longer and slightly stiffer. The long erect hairs on the alitrunk slightly more numerous, numbering 5-6 pairs, varying in length, the long pair gracing the humeri stiff and not attenuated as are the corresponding hairs of lewisi.

(6) Postpetiole relatively slightly broader than in lewisi, about half again as broad as long.

(7) Spongiform appendages less voluminous on both nodes; the lateral lobes on the petiolar node reaching only halfway or a little more up the sides of the node (reaching to or nearly to the anterior nodal face in lewisi).

(8) A broad area just behind the costulae on the first gastric tergite feebly and superficially reticulate and subopaque, remainder of the segment shining (in lewisi gastric tergite I, is smooth and shining except for the basal costulae).

(9) Descending border of propodeal lamellae slightly excised below upper acute toothlike portion, convex ventrally (upper corner bluntly rectangular in lewisi, not toothlike ; descending border straight or nearly straight above, weakly rounded below).

(10) Antennae much longer and more slender throughout; Scape L 0.50 mm., funiculus L 0.64 mm.

(11) Color medium ferrugineous, perhaps slightly darker than is usual in lewisi.

Bolton (2000) - TL 2.9-3.0, HL 0.74-0.77, HW 0.49-0.53, CI 66-69, ML 0.36-0.40, MI 49-52, SL 0.49-0.52, SI 98-100, PW 0.28-0.29, AL 0.76-0.80 (2 measured).

Characters of smythiesii-complex. Apicoscrobal hair stiff; anterior to this there are no freely projecting hairs but posteriorly there are 2-3 similar stiff hairs on the dorsolateral margin of the occipital lobe. In profile cephalic dorsum with a transverse row of erect hairs at the occipital margin; anterior to this with inclined ground-pilosity but without a pair of erect hairs near highest point of vertex. Pronotal humeral hair stiff and simple, straight or slightly curved. Pronotal dorsum with 1 pair and mesonotum with 3 pairs of erect simple hairs. Entire dorsal alitrunk finely and densely punctate to reticulate-punctate except for anterior half of propodeal dorsum which is usually smooth; sculpture may be somewhat effaced posteromedially on pronotum. Lamella on propodeal declivity becoming broader basally, its posterior (free) margin distinctly convex in the lower half. With petiole in profile the lateral spongiform lobe terminates at about the midlength of the node, not reaching the anterior face of the node. Dorsum of petiole node finely and densely punctate to reticulate-punctate; disc of postpetiole smooth. Erect hairs on first gastral tergite not restricted to a transverse row near base and another near apex. Basigastral costulae distinct on first gastral tergite.

Queen
Gynetype. TL 3.56 mm., HL 0.78 mm., WL 0.94 mm., CI 71, MI 52, ICD 45.

Type Material
The holotype worker, gynetype female and the smaller paratype worker were taken, according to Dr. Yasumatsu, in a cave near Saruta, Shikoku (J. Ishikawa). An additional worker (the larger of the two paratypes) was taken in U. S. Plant Quarantine at Seattle, Washington in cargo originating from an unknown locality in Japan. This latter specimen reached me through the courtesy of Dr. M. R. Smith, and it will be returned to the collection of the U. S. National Museum. The holotype and gynetype will be returned to Dr. Yasumatsu at the University of Kyushu, and the renaming paratype will be deposited in the collection of the Museum of Comparative Zoology, Cambridge, Massachusetts, U.S.A.

Bolton (2000) - Holotype worker, paratype worker and queen, JAPAN: Shikoku, nr Saruta, in cave (J. Ishikawa); paratype worker, U. S. A.: Washington, Seattle, Plant Quarantine, in cargo from Japan [examined].

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