Aenictus cylindripetiolus

Aenictus cylindripetiolus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Dorylinae
Genus:	Aenictus
Species:	A. cylindripetiolus
Binomial name
Aenictus cylindripetiolus Jaitrong & Yamane, 2013

This species mainly inhabits lowland primary forests; only one colony was collected from a longkong orchard. The type series was found under a log in a rainforest during the rainy season. No worker activity was seen around the log and no immatures were found in the bivouac.

Identification

A member of the ceylonicus group. Aenictus cylindripetiolus is similar to Aenictus thailandianus in having a mandible with more than 4 teeth, and entirely sculptured promesonotum. (Jaitrong and Yamane 2013)

Keys including this Species

• Key to southeastern Asian Aenictus ceylonicus group species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Singapore.
Oriental Region: Thailand (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Explore Overview of Aenictus biology  Little is known about the biology of Aenictus cylindripetiolus. The genus is comprised of species that live an army ant lifestyle. Aenictus typically prey on other ants, from other genera, or other insects such as wasps or termites. There are reports of Aenictus preying on other insects as well and even have been observed collecting honeydew from homopterans (Santschi, 1933; Gotwald, 1995) but this appears, at least from available evidence, to be uncommon. Foraging raids can occur day or night across the ground surface. Occasionally raids are arboreal. During a raid numerous workers attack a single nest or small area, with several workers coordinating their efforts to carry large prey items back to the nest or bivouac. Aenictus have a nomadic life style, alternating between a migratory phase in which nests are temporary bivouacs in sheltered places above the ground and a stationary phase where semi-permanent underground nests are formed. During the nomadic phase bivouacs move regularly, sometimes more than once a day when larvae require large amounts of food. Individual nests usually contain up to several thousand workers, although nest fragments containing only a few hundred workers are often encountered. Queens are highly specialised and look less like workers than in most ant species. They have greatly enlarged gasters (dichthadiform) and remain flightless throughout their life. New colonies are formed by the division of existing colonies (fission) rather than by individual queens starting colonies on their own. ‎

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• cylindripetiolus. Aenictus cylindripetiolus Jaitrong & Yamane, 2013: 180, fig. 5A-G (w.q.) THAILAND.
  • Type-material: holotype worker, 27 paratype workers, 1 paratype queen.
  • Type-locality: holotype Thailand: Trang Prov., NaYong Dist., Khao Chong Botanical Garden, 10.viii.2009, WJT09-TH2023, evergreen forest (W. Jaitrong); paratypes with same data.
  • Type-depositories: TNHM (holotype); BMNH, MCZC, SKYC, TNHM (paratypes).
  • Status as species: Khachonpisitsak, et al. 2020: 26; Wang, W.Y., Soh, et al. 2022: 30.
  • Distribution: Singapore, Thailand.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

(holotype and paratypes, n = 10). TL 2.90–3.15 mm; HL 0.60–0.65 mm; HW 0.60–0.65 mm; SL 0.53–0.58 mm; ML 0.98–1.05 mm; PL 0.26–0.28 mm; CI 100–102; SI 88–92.

Head in full-face view subrectangular, almost as long as broad, sides weakly convex, posterior margin almost straight or feebly convex. Antennal scape relatively long, slightly extending beyond 2/3 of head length. Frontal carina relatively long, extending beyond the level of posterior margin of torulus. Parafrontal ridge feeble and incomplete. Anterior clypeal margin weakly concave, concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with large acute apical tooth followed by a medium-sized subapical tooth, 2 denticles, and a medium-sized basal tooth; basal margin feebly concave. Maximum width of gap between anterior clypeal margin and mandibles about 1.4 times as broad as maximum width of mandible. Promesonotum convex dorsally and sloping gradually to metanotal groove; mesopleuron relatively short, demarcated from metapleuron by a shallow groove; metapleural gland bulla relatively small, its maximum diameter about 1.7 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with straight dorsal outline; propodeal junction acutely angulated, overhanging declivitous face; declivity of propodeum broadly and shallowly concave, encircled with a distinct rim. Petiole cylindrical, distinctly longer than high, with its dorsal outline slightly elevated posteriorly, posterior face of petiole flat, and encircled with an indistinct carina; subpetiolar process generally weakly developed, with its ventral outline sinuate, and anteroventral corner acutely angulated. Postpetiole almost as long as petiole, seen in profile with its dorsal outline slightly elevated posteriorly and its ventral outline concave.

Head and gaster entirely smooth and shiny. Mandible very finely striate. Antennal scape superficially reticulate. Mesosoma entirely reticulate, but the sculpturation on pronotum weaker than elsewhere; mesopleuron with longitudinal rugae. Petiole and postpetiole entirely reticulate. Legs entirely smooth and shiny except basal portions of femora and tibiae superficially microreticulate.

Head and mesosoma dorsally with relatively sparse standing hairs mixed with sparse shorter hairs; longest pronotal hair 0.15-0.18 mm long. Head including antennal scape reddish brown; mandible, mesosoma, petiole, and postpetiole dark reddish brown; gaster and legs yellowish brown; mesosoma reddish brown.

Queen

(paratype). TL 6.15 mm; HL 1.03 mm; HW 1.18 mm; SL 0.58 mm; ML 1.68 mm; PL 0.50 mm; CI 115; SI 49.

Head in full-face view subrectangular, slightly shorter than broad, with sides weakly convex, posterior margin weakly concave. Head with a weakly impressed furrow from tip of indistinct frontal carina to occipital margin. Antennal scape relatively short, about half as long as the head, basally narrow, gradually widening apicad; antennal segments II-X each longer than broad; II-V almost of same length. Frontal carina indistinct. Parafrontal ridge absent. Anterior clypeal margin almost straight. Mandible half as long as head, subfalcate, slender, broadest at base, with sharp apex; masticatory margin lacking denticles. Mesosoma rather stout, its dorsal outline almost flat; pronotum and mesonotum fused, with a very shallow suture between them; pronotum slightly broader than mesonotum and propodeum, its median part strongly steeply declining anteriorly; metanotal groove recognizable but shallow; propodeal declivity almost flat, not encircled by a rim. Petiole slightly shorter than high, with its dorsal outline slightly elevated posteriorly, anterior face of petiole concave and posterior face flat; subpetiolar process large, subrectangular, anterior corner and posterior corner each bluntly angulate. Gaster large and elongate; first tergite narrower and much shorter than second, with a very shallow furrow running longitudinally; second tergite longest; third as long as fourth; pygidium small, triangular, with subtruncate tip. Legs relatively long and slender; femora and tibiae clavate.

Entire body smooth and shiny except for lateral face of propodeum and propodeal declivity superficially reticulate but shiny.

Entire body with relatively dense standing hairs; hairs slightly shorter on pronotum than on head, mandible and antennal scape; longest pronotal hair 0.15-0.18 mm long. Head including antennal scape and clypeus yellowish brown; mandible slightly darker; lower gena and large marking on upper frons and vertex dark brown. Mesosoma with ground colour yellowish brown; lateral faces of pronotum and mesonotum, and posterior 2/3 of dorsum of mesonotum dark brown; anterior slope of pronotum reddish brown with a pair of black spots below. Mesopleuron, metapleuron and lateral face of propodeum partly darker. Anterior face of petiole yellowish brown; posterior face extensively and lateroventral portion dark reddish brown; gaster with ground colour yellowish brown to reddish brown; seen from above first tergite with a median spot connected to dark apical band; second tergite with a large triangular median marking, third and fourth tergites with a basal band that is medially widened. Legs yellowish brown.

Type Material

Holotype. THAILAND: Worker from S. Thailand, Trang Prov., Na Yong Dist., Khao Chong Botanical Garden, evergreen forest, 10.VIII.2009, leg. W. Jaitrong, WJT09-TH2023 (THNHM). Paratypes. Twenty-seven workers, same data as holotype (BMNH, MCZC, SKYC, THNHM) and one queen, same data as holotype (THNHM).

Etymology

The specific name refers to the cylindrical petiole of the worker.

References

• Dhadwal, T., Bharti, H. 2023. Aenictus dirangensis sp. nov. (Hymenoptera: Formicidae), a new species of Aenictus ceylonicus group from India. Journal of the Entomological Research Society 25(2): 387-403 (doi:10.51963/jers.v25i2.2367).
• Jaitrong, W. & Yamane, S. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31:165-233.
• Khachonpisitsak, S., Yamane, S., Sriwichai, P., Jaitrong, W. 2020. An updated checklist of the ants of Thailand (Hymenoptera, Formicidae). ZooKeys 998, 1–182 (doi:10.3897/zookeys.998.54902).
• Wang, W.Y., Soh, E.J.Y., Yong, G.W.J., Wong, M.K.L., Benoit Guénard, Economo, E.P., Yamane, S. 2022. Remarkable diversity in a little red dot: a comprehensive checklist of known ant species in Singapore (Hymenoptera: Formicidae) with notes on ecology and taxonomy. Asian Myrmecology 15: e015006 (doi:10.20362/am.015006).

References based on Global Ant Biodiversity Informatics

• Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
• Jaitrong W. 2015. A revision of the Thai species of the ant genus Aenictus Shuckard, 1840 (Hymenoptera: Formicidae: Dorylinae). The Thailand Natural History Museum Journal 9(1): 1-94.
• Jaitrong W., and S. Yamane. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31: 165-233.