Aenictus siamensis

Aenictus siamensis
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Dorylinae
Genus:	Aenictus
Species:	A. siamensis
Binomial name
Aenictus siamensis Jaitrong & Yamane, 2011 Specimen Labels

Aenictus siamensis is found in highland (700–900 m alt.) seasonal forests (hill evergreen forest and dry evergreen forest) and open areas. A colony from Loei Province was collected at night, a colony from Chiang Mai Province during the day. The type series and a colony from Doi Suthep-Pui National Park, Chiang Mai Province were collected using pitfall traps.

Identification

Jaitrong and Yamane (2011) - A member of the laeviceps species group.Aenictus siamensis is similar to Aenictus binghamii in having the mesosoma extensively sculptured, but is much smaller than the latter. Furthermore the pronotal sculpture is much weaker (dorsum almost smooth) in the latter.

Keys including this Species

• Key to Aenictus laeviceps group species

Distribution

Distribution based on Regional Taxon Lists

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 siamensis. 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.

• siamensis. Aenictus siamensis Jaitrong & Yamane, 2011: 42, figs. 35-37 (w.) THAILAND.
  • Type-material: holotype worker, 18 paratype workers.
  • Type-locality: holotype Thailand: Chaiyaphum Prov., Phu Kheao Dist., 27.iii.1999, WJT99-TH55, hill evergreen forest (W. Jaitrong); paratypes with same data.
  • Type-depositories: TNHM (holotype); BMNH, FFKT, MCZC, MHNG, SKYC, TNHM (paratypes).
  • Distribution: Thailand.

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

Description

Worker

Measurements. Holotype and paratypes (n = 10): TL 3.75–3.90 mm; HL 0.78–0.85 mm; HW 0.63–0.70 mm; SL 0.68–0.75 mm; ML 1.18–1.25 mm; PL 0.25–0.28 mm; CI 81–82; SI 107–108.

Holotype and paratypes - Head in full-face view distinctly longer than broad, with sides convex and posterior margin almost straight; occipital carina complete. Antennal scape relatively long, reaching the posterolateral corner of head; antennal segments II–X each longer than broad; II almost as long as each of III–VI. Frontal carina very short, not extending beyond the level of posterior margin of torulus. Anterior margin of clypeus convex, bearing 8–9 denticles. Masticatory margin of mandible with a large apical tooth followed by a medium-sized subapical tooth, 6–7 denticles, and often 1 or 2 small basal teeth; basal margin lacking denticles. Mesosoma relatively slender; promesonotum in profile weakly convex dorsally and sloping gradually to metanotal groove; dorsal outline of propodeum feebly convex; propodeal junction angulate; declivity shallowly concave, encircled by a thin rim. Petiole subsessile, its node almost as long as high with strongly convex dorsal outline; subpetiolar process well developed and triangular with apex directed downward; postpetiole almost as long as petiole, the node similar to that of petiole in shape.

Entire head smooth and shiny. Mandible very finely striate except along masticatory and outer margins. nal scape superficially sculptured and shiny. Pronotum dorsally almost smooth and shiny; lateral face superficially reticulate and weakly shiny; mesothorax, metapleuron and propodeum densely punctate; mesothorax and propodeum often with ill-defined longitudinal rugulae on lateral faces. Petiole with dense small punctures; postpetiole entirely smooth and shiny. Legs extensively smooth and shiny.

Head and mesosoma dorsally with relatively sparse standing hairs mixed with sparse short hairs over the surface; longest pronotal hair 0.23–0.27 mm long. Entire body dark reddish brown. Typhlatta spot located anterior to occipital corner.

Type Material

Holotype worker from NE. Thailand, Chaiyaphum Prov., Phu Kheao Dist., Hill evergreen forest, 27 III 1999, W. Jaitrong leg., WJT99-TH55 (Natural History Museum of the National Science Museum). Eighteen paratype workers, same data as holotype (Ant Museum, The Natural History Museum, Museum of Comparative Zoology, Musee d'Histoire Naturelle Genève, SKY Collection, THNHM).

Etymology

The specific name is an adjective meaning ‘of Siam (old name of Thailand)’.

References

• Jaitrong, W. & Yamane, S. 2011. Synopsis of Aenictus species groups and revision of the A. currax and A. laeviceps groups in the eastern Oriental, Indo-Australian, and Australasian regions (Hymenoptera: Formicidae: Aenictinae). Zootaxa, 3128, 1–46.
• 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).

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.