Aenictus inflatus

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Aenictus inflatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species: A. inflatus
Binomial name
Aenictus inflatus
Yamane & Hashimoto, 1999

Aenictus inflatus casent0249279 p 1 high.jpg

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Specimen Labels

Remarkable for the genus in having a polymorphic worker caste, and an inflated propodeum (found filled with red liquid in the type colony) in larger workers. The smaller workers possess narrower heads with the sides almost parallel, very short antennae and legs, and normal propodea.

Identification

The only member of the inflatus species group.

Key to Aenictus species groups

Distribution

Distribution based on Regional Taxon Lists

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


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Yamane and Hashimoto reported the following about the colony from which the types were collected: In March 1997 during a night walk in the jungle we found a raiding column of a strange yellowish army ant in the Lambir Hills National Park, Sarawak, Borneo. Surprisingly the workers had distinctly inflated propodea that were filled up with a red liquid. When we collected workers from the column running down from the canopy very small workers, though few in number, were witnessed. A close examination of these small individuals under a binocular microscope revealed that they are clearly distinguished from the majority of workers by the lack of propodeal inflation and possession of very short antennae and legs. Since intermediate specimens were also found, this species may not be typically dimorphic. But it must be the first polymorphic Aenictus species with the peculiar propodeal inflation in larger specimens.

Allometric growth pattern in some body parts (see description) shows that this species is polymorphic (and almost dimorphic) in its worker caste. The small workers are more similar to usual workers of Aenictus species than are larger ones. They are easily distinguished from small species such as Aenictus piercei, Aenictus minutulus etc. by the long head with parallel sides and weak body sculpture (only mesothorax distinctly sculptured). Their function is not known. However, since they are few in number (ca. 3.3% of all the workers captured), there is a possibility that they are a mere expression of ancestral form of this species owing to the short supply of food during their larval stage. This situation is quite different from that described by Topoff (1971) for Aenictus laeviceps in which the smaller workers predominate in number.

Little is known about the biology of Aenictus inflatus. 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. Aenictus inflatus is unusual within the genus as it has a distinctly polymorphic worker caste. The majority of Aenictus species are monomorphic, with a few exhibiting some weak polymorphism.

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • inflatus. Aenictus inflatus Yamane & Hashimoto, 1999: 428, fig. 1 (w.) BORNEO.

Description

References