Aenictus pinkaewi

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

So far this species is known only from highlands. Workers carry out their raids and immigrations on the ground surface in highly varied situations from open areas, secondary forest to deep forest interiors during the day and night. The type series was collected by pitfall traps in a secondary forest. W. Jaitrong observed this species preying on ants of the genus Pheidole. (Jaitrong and Yamane 2013)

Identification

A member of the ceylonicus group. Jaitrong and Yamane (2013) - Aenictus pinkaewi is similar to Aenictus fuchuanensis, Aenictus maneerati, and Aenictus sundalandensis in having the long cylindrical petiole and short head (CI 100-112). It is most similar to A. fuchuanensis.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: Thailand (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about the biology of Aenictus pinkaewi. 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 New General Catalogue, a catalogue of the world's ants.

  • pinkaewi. Aenictus pinkaewi Jaitrong & Yamane, 2013: 207, figs. 16A-C (w.) 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 2.90–3.35 mm; HL 0.60–0.69 mm; HW 0.65–0.75 mm; SL 0.45–0.58 mm; ML 0.93–1.10 mm; PL 0.23–0.29mm; CI 105–109; SI 69–82.

Head in full-face view subrectangular, slightly shorter than broad, sides feebly convex, and posterior margin feebly concave. Antennal scape reaching 2/3 of head length; antennal segments II-VI each distinctly longer than broad, of approximately same length; terminal segment (X) slightly longer than VII+VIII+IX. Frontal carina short, reaching the level of posterior margin of torulus. Parafrontal ridge absent. Anterior clypeal margin almost straight or feebly concave, lacking denticles, concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with 4 teeth including a large apical tooth; basal margin feebly concave, lacking denticles. Maximum width of gap between anterior clypeal margin and mandibles about 1.9 times as broad as maximum width of mandible. Promesonotum strongly convex dorsally and sloping gradually to metanotal groove; metanotal groove indistinct; mesopleuron demarcated from metapleuron by a shallow groove; metapleural gland bulla relatively small, its maximum diameter about 1.6 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with almost straight dorsal outline; propodeal junction angulate, overhanging the declivitous face of propodeum; the declivity broadly and shallowly concave, encircled with a rim. Petiole cylindrical, distinctly longer than high, with its dorsal outline slightly elevated posteriorly; posterior face of petiole shallowly concave, and encircled with a thin carina; subpetiolar process generally very low, with its anteroventral corner acutely angulate, and ventral outline feebly convex. Postpetiole almost as long as petiole, node convex dorsally and elevated posteriorly.

Head and gaster entirely smooth and shiny. Mandible very finely striate. Antennal scape superficially microreticulate, but shiny. Promesonotum entirely punctate; mesopleuron, metapleuron and propodeum punctate; in addition, upper portion of mesopleuron, upper portion of metapleuron, and lateral face of propodeum with longitudinal rugae. Petiole and postpetiole densely reticulate. Legs entirely smooth and shiny except basal portion of femora densely micropunctate.

Head and mesosoma dorsally with relatively dense standing hairs mixed with sparse short decumbent hairs; longest pronotal hair 0.23–0.25 mm long. Head including antennal scape and mandible, petiole and postpetiole dark reddish brown; mesosoma dark brown; gaster dark reddish brown; tip and lateral face of gaster, and legs yellowish brown.

Type Material

Holotype. THAILAND: Worker from N. Thailand, Chiang Mai Prov., Muang Dist., near Chiang Mai University, VI.2000, leg. W. Jaitrong, WJT00-CM01 (THNHM). Paratypes. Forty workers, same data as holotype (BMNH, MCZC, SKYC, THNHM).

Etymology

The specific name is dedicated to Dr. Nantasak Pinkaew of Kasetsart University, who helped us during our field works in Thailand.

References