Aenictus eguchii

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

Little is known about the bionomics of A. eguchii. However, judging from the data for the specimens examined this species inhabits lowland primary forests.

Identification

A member of the ceylonicus group. Jaitrong and Yamane (2013) - Aenictus eguchii is most similar in general appearance to Aenictus jawadwipa from Sundaland. However, they differ in some characters. The posteroventral corner of the subpetiolar process is bluntly angulate (not spiniform) in the former, but acutely angulate (spiniform) in the latter. The dorsal outline of the propodeum is straight in the latter but weakly convex in the former. The metapleural gland bulla is more strongly sculptured (puncto-reticulate and opaque) in the former than in the latter (weakly sculptured and shiny). The promesonotum in profile is more distinctly convex in the former than in the latter.

Keys including this Species

• Key to southeastern Asian Aenictus ceylonicus group species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: Vietnam (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 eguchii. 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. ‎

Castes

Known only from the worker caste.

Nomenclature

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

• eguchii. Aenictus eguchii Jaitrong & Yamane, 2013: 183, fig. 6A-C (w.) VIETNAM.
  • Type-material: holotype worker, 17 paratype workers.
  • Type-locality: holotype Vietnam: Ha Tai Prov., Ba Vi N.P. (ca 400 m.), 12.xi.1999, Eg99-VN-126 (K. Eguchi); paratypes with same data.
  • Type-depositories: VNMN (holotype); BMNH, MCZC, SKYC, TNHM (paratypes).
  • Distribution: Vietnam.

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 2.20–2.60 mm; HL 0.46–0.58 mm; HW 0.43–0.55 mm; SL 0.30–0.43 mm; ML 0.70–0.85 mm; PL 0.18–0.23 mm; CI 92–96; SI 71–77.

Head in full-face view subrectangular, slightly longer than broad, sides convex and posterior margin almost straight. Antennal scape reaching 2/3 of head length. Frontal carina relatively long, slightly extending beyond the level of posterior margin of torulus. Parafrontal ridge absent. Anterior clypeal margin almost straight, lacking denticles and 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 almost straight. Maximum width of gap between anterior clypeal margin and mandibles about 2.1 times as broad as maximum width of mandible. Promesonotum weakly convex dorsally and sloping gradually to metanotal groove; metanotal groove indistinct; metapleural gland bulla relatively large and transparent, its maximum diameter about 2.8 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with almost straight or feebly concave dorsal outline; propodeal junction angulated, nearly right-angled; declivity of propodeum shallowly concave, and encircled with a rim. Petiole almost as long as high, with its dorsal outline weakly convex; subpetiolar process generally very low, subrectangular with its anteroventral and posteroventral corners angulate, and margin between the corners almost straight. Postpetiole almost as long as petiole, with its dorsal outline convex.

Head including antennal scape entirely smooth and shiny. Promesonotum smooth and shiny except for punctate anteriormost portion; mesopleuron, metapleuron, and propodeum entirely punctate; in addition, mesopleuron with longitudinal rugae. Petiole and postpetiole entirely reticulate except small area on dorsa smooth and shiny. Legs entirely smooth and shiny.

Head and mesosoma dorsally with relatively dense standing hairs; longest pronotal hair 0.20–0.23 mm long. Head, mesosoma, petiole, and postpetiole reddish brown; gaster and legs yellowish brown.

Type Material

Holotype. VIETNAM: Worker from N. Vietnam, Ha Tai Prov., Ba Vi N.P. (ca. 400 m alt.), 12.XI.1999, leg. K. Eguchi, Eg99-VN-126 (VNMN). Paratypes. Seventeen workers, same data as holotype (BMNH, MCZC, SKYC, THNHM).

Etymology

The scientific name is dedicated to Dr. Katsuyuki Eguchi, who donated the type series to us.

References

• Antony, A.K., Prasad, G. 2022. Two new species of army ants of the Aenictus ceylonicus group (Hymenoptera: Formicidae) from Kerala, India. Journal of Threatened Taxa 14(3): 20780-20785 (doi:10.11609/jott.6962.14.3.20780-20785).
• 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.

References based on Global Ant Biodiversity Informatics

• Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
• Eguchi K., B. T. Viet, and S. Yamane. 2014. Generic Synopsis of the Formicidae of Vietnam (Insecta: Hymenoptera), Part II—Cerapachyinae, Aenictinae, Dorylinae, Leptanillinae, Amblyoponinae, Ponerinae, Ectatomminae and Proceratiinae. Zootaxa 3860: 001-046.