Aenictus appressipilosus

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

Known only from lowland rainforests of Borneo. Seiki Yamane collected the type series at night.

Identification

A member of the ceylonicus species group. Jaitrong and Yamane (2013) - Aenictus appressipilosus is a distinct species within the group in having 2 long standing hairs mixed with few short appressed hairs on the vertex and has a few appressed hairs mixed with few decumbent hairs on promesonotum (the other species have sparse to dense long standing hairs on head and pronotum).

Keys including this Species

• Key to southeastern Asian Aenictus ceylonicus group species

Distribution

Borneo (Sabah)

Distribution based on Regional Taxon Lists

Indo-Australian Region: Malaysia (type locality), Philippines.

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 appressipilosus. 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.

• appressipilosus. Aenictus appressipilosus Jaitrong & Yamane, 2013: 172, fig. 1A-C (w.) BORNEO (East Malaysia: Sabah).
  • Type-material: holotype worker, 8 paratype workers.
  • Type-locality: holotype Malaysia: Borneo, Sabah, Tawau Hills N.P., 7.vii.1996, SB96-SKY-01 (Sk. Yamane); paratypes with same data.
  • Type-depositories: MBSM (holotype); SKYC, TNHM (paratypes).
  • Distribution: Malaysia (Sabah).

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 = 9). TL 2.70-2.85 mm; HL 0.58-0.60 mm; HW 0.54-0.55 mm; SL 0.45-0.48 mm; ML 0.90-0.95 mm; PL 0.25 0.28 mm; CI 92-93; SI 84-88.

Head in full-face view clearly longer than broad, anterior portion slightly broader than posterior portion, sides convex, posterior margin almost straight; occipital margin bearing a carina. Antennal scape relatively long, extending beyond 2/3 of head length but not reaching posterolateral corner of head. Frontal carina relatively long, slightly extending beyond the level of posterior margin of torulus. Parafrontal ridge indistinct, slightly extending beyond the level of posterior margin of torulus. Anterior clypeal margin almost straight or feebly concave. Masticatory margin of mandible with large acute apical tooth followed by a medium-sized subapical tooth, and 5-6 denticles; basal margin almost straight. Maximum width of gap between anterior clypeal margin and mandibles about 1.8 times as broad as maximum width of mandible. Promesonotum convex dorsally and sloping gradually to metanotal groove; metanotal groove indistinct; mesopleuron relatively long, not clearly demarcated from metapleuron; metapleural gland bulla relatively small, its maximum diameter about 1.8 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with straight dorsal outline; propodeal junction acutely angulate, overhanging the declivitous face; declivity of propodeum seen from back tapering above, shallowly concave, and encircled with a thin rim. Petiole in profile trapezoidal, slightly longer than high, with straight dorsal outline; anterior slope of petiole seen in profile feebly concave; subpetiolar process low with anterior corner angulated and posteroventrally produced into a spine with acute tip, margin connecting anterior corner and base of the spine weakly concave. Postpetiole shorter than petiole, with its dorsal outline convex.

Head and gaster entirely smooth and shiny. Mandible very finely striate. Antennal scape superficially microreticulate, apical half slightly shiny. Mesosoma reticulate (reticulation coarser on lateral face of pronotum than on propodeum) except for anteriormost portion of pronotum punctate; promesonotal dorsum smooth and shiny; mesopleuron with relatively irregular longitudinal rugae.

Head with a pair of long standing hairs mixed with sparse short appressed hairs over the surface; mesosoma dorsally with relatively sparse appressed hairs mixed with 2-4 decumbent hairs; longest pronotal hair (decumbent hair) 0.10-0.13 mm long. Antennal scape, mesosoma, petiole and postpetiole reddish brown; head, gaster and legs yellowish brown.

Type Material

Holotype. MALAYSIA: Worker from E. Malaysia, Borneo, Sabah, Tawau Hills N.P., 7.VII.1996, leg. Sk. Yamane, SB96-SKY-01 (UMS). Paratypes. Eight workers, same data as holotype (SKYC, THNHM).

Etymology

The specific name refers to the appressed hairs on promesonotum.

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.
• Huong N. T. T., P. V. Sang, and B. T. Viet. 2015. A preliminary study on diversity of ants (Hymenoptera: Formicidae) at Hon Ba Nature Reserve. Environmental Scientific Conference 7: 614-620.
• Jaitrong W., and S. Yamane. 2013. The Aenictus ceylonicus species group (Hymenoptera, Formicidae, Aenictinae) from Southeast Asia. Journal of Hymenoptera Research 31: 165-233.