Gnamptogenys menadensis

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Gnamptogenys menadensis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ectatomminae
Tribe: Ectatommini
Genus: Gnamptogenys
Species: G. menadensis
Binomial name
Gnamptogenys menadensis
(Mayr, 1887)

Gnamptogenys-menadensisL3.2.jpg

Gnamptogenys-menadensisD3.2.jpg

Synonyms

G. menadensis is most commonly found in mesic forested areas. It forages on foliage and nests in a range of locations including in trees and shrubs, rotting wood, tree fern stems, under moss on rocks and in soil. Arboreal nests are constructed in preexisting cavities and sealed with a lining of organic material. Colonies are generally small, with an average of a few hundred workers. Numerous aspects of the biology and natural history of this common species have been studied.

At a Glance • Gamergate  

 

Identification

Lattke (2004) - This species is easily confused with Gnamptogenys bicolor, having similar sculpturing patterns, well developed occipital lobes, and posteriorly placed eyes. G. bicolor differs from G. menadensis by the longitudinally strigulose median area on the promesonotum, the propodeal declivity with a posteromedian raised area and anteriorly diverging sides, and a usually straight metacoxal tooth. G. bicolor generally has more foveolae on the postpetiole, which are deeper and larger in diameter than in G. menadensis; the sides of the fourth abdominal tergite in G. bicolor likewise have larger punctae. G. bicolor has abundant long standing hairs on the mesosomal dorsum when seen in lateral view with background lighting, in contrast to their virtual absence in G. menadensis.

This species may be part of a species complex (see the nomenclature section below).

Keys including this Species

Distribution

Lattke (2004) - G. menadensis is a relatively common ant found in the Philippines, southwest into Indonesia, and reaching its western range limit in northeastern peninsular Malaysia. There is a single record from New Guinea. Its range is mostly east of and separated from that of the similar Gnamptogenys bicolor, though they are sympatric in western Malaysia and Sumatra. G. bicolor is a Southeast Asian ant found from Myanmar eastward, including southern China.

Distribution based on Regional Taxon Lists

Indo-Australian Region: Borneo, Indonesia (type locality), Malaysia, New Guinea, Philippines (type locality), Sulawesi.
Oriental Region: India, Thailand.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Habitat

Commonly found in mesic forest.

Biology

Lattke notes:

Most reproduction in G. menadensis is through gamergates (Gobin et al. 1998a).

G. menadensis from Ulu Gombak nest in the ground and have an average of 500 workers, in contrast to the arboreal habits and smaller nests of G. menadensis from Sulawesi (F. Ito, pers. com.). Thus specimens recognized here as G. menadensis may belong to more than one species, but no consistent morphological differences were detected during the course of this study.

Most habitat labels indicate collection from mesic forested areas. In the Philippines G. menadensis commonly forages on foliage, with nests being found in rotting wood, in tree fern stems, and under moss on rocks (Brown 1954b). In Sulawesi, Indonesia, the ants are arboreal, with foraging and nesting on trees and shrubs. Nests are constructed in preexisting cavities and sealed with a lining of organic material. Colonies are generally small, with an average of 100 workers (Gobin, Peeters, and Billen 1998a). Occasional nesting sites included cavities in limestone rocks and rattan palm leaf shafts. Nests eventually split by budding/fission. Besides hunting for prey, workers also bite flowering buds and lick the exuding sap (Gobin, Peeters, and Billen 1998a). Foragers use chemical trails to home to their nests as well as to recruit to foraging areas (Gobin et al., 1998) by sting-tapping on the substrate. Virgin workers in this species produce trophic eggs (Gobin, Peeters, and Billen 1998b).

Foraging behavior has been studied in this species (also see Poneroid Foraging). The abstract of Johnson et al. (2003) - Gnamptogenys menadensis is an arboreal nester that forages opportunistically almost exclusively on vegetation, sometimes recruiting others to participate in prey retrieval. The three-dimensional characteristics of vegetation suggest that functions describing recruitment decision thresholds or the pattern of recruitment in arboreal species may differ from those predicted by optimal foraging theory. To examine the effects of prey abundance and distance on the recruitment dynamics of G. menadensis, we baited nests with one termite, five termites or a number of termites between 20 and 40 either near to or far from the entrance and observed the ensuing behaviors. G. menadensis recruited others when encountering multiple termites regardless of the termite pile’s distance from the nest, although a few individuals remained at the site and defended the resource. The pattern of arrivals at the site indicates that the majority and sometimes all arrivals were recruited from the branch trails. In combination, these results suggest that the architecture of the foraging habitat, which limits available return routes to the nest and thus increases encounter probabilities with potential recruits, shaped the process of information transfer and generated a collective pattern of foraging and prey retrieval.

Workers of Polyrhachis rufipes use the trails of G. menadensis to gain access to sugar sources. When they encounter Gnamptogenys foragers, P . rufipes workers show a typical aggressive antennal boxing, to which Gnamptogenys reacts with a submissive behavior (Gobin, Peeters, and Billen 1998b).

Reproduction The majority of colonies of G. menadensis in Sulawesi lack queens and several workers mate and reproduce instead (‘gamergates’). Virgin workers lay morphologically specialized trophic eggs which are fed to larvae (Gobin, Peeters, and Billen 1998c). Some of these virgins switch to male eggs when gamergates are experimentally removed. Three distinct patterns of oogenesis thus result in: (1) trophic eggs; (2) reproductive eggs (unfertilized) laid by virgin workers; and (3) reproductive eggs laid by gamergates, whose ovarioles are always longer than those of virgin workers. Gobin, Peeters, and Billen (1999) investigated the behavioural regulation of ovarian activity in virgin workers by temporarily excluding gamergates. In 12 groups of 35–45 virgins, a few workers became dominant and started to lay reproductive eggs. Once gamergates were reintroduced, sterile workers attacked and immobilized workers with enlarged ovaries (confirmed by dissection of 173 individuals), which often died as a result. Gamergates were never aggressive towards new egg layers. Aggression was not triggered by divergence in colony odours, as it was absent in control experiments in which six colonies were divided in half, with each part containing gamergates, and reunited after 50 days. Our results show that sterile workers discriminate against new egg layers, given that their ovaries are not as developed as those of gamergates. Olfactory detection of different levels of ovarian activity thus appears possible. Mesh experiments indicated that the putative pheromones are nonvolatile and require physical contact for transmission. Aggressive behaviour directed at reproducing workers can be interpreted as worker policing. In G. menadensis, worker policing results in virgins laying only trophic eggs.

Different levels of ovarian activity in G. menadensis. From Gobin et al. (1999)

Castes

Winged queens exist but they are infrequent in Sulawesi, and most colonies reproduce with several gamergates (Gobin et al. 1998a).

Nomenclature

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

  • menadensis. Ectatomma (Stictoponera) menadensis Mayr, 1887: 539 (footnote) (w.) INDONESIA (Sulawesi). Wheeler, G.C. & Wheeler, J. 1964b: 450 (l.); Imai, Brown, et al. 1984: 67 (k.); Lattke, 2004: 131 (q.m.). Combination in Stictoponera: Emery, 1900d: 663; in Gnamptogenys: Brown, 1958g: 228. Senior synonym of obscura, stylata: Brown, 1954h: 2.
  • stylata. Stictoponera stylata Menozzi, 1925c: 440, fig. 2 (w.) PHILIPPINES. Junior synonym of menadensis: Brown, 1954h: 2.
  • obscura. Stictoponera menadensis var. obscura Santschi, 1932b: 11 (w.) INDONESIA (Sulawesi). [Unresolved junior secondary homonym of obscurum Emery, above.] Junior synonym of menadensis: Brown, 1954h: 2.

Type Material

Taxonomic Notes

Lattke 2004 Gnamptogenys fig 45-49

Lattke (2004) - Occipital lobes prominent, projecting posteroventrally in lateral view; eyes situated on posterior half of head, usually less than one ocular diameter distant from vertex. Mesosomal dorsum mostly densely foveolate to areolate with median longitudinal strip of smooth cuticle, devoid of foveolae on mesonotum; mesosomal dorsal margin mostly devoid of standing hairs in lateral view; propodeal declivity medially with raised posteriorly surface with parallel lateral margins. Metacoxal teeth robust and curved.

There are field data and behavioral information from Fuminori Ito and Bruno Gobin (pers. com.) that suggest the presence of more than one species identifiable as G. menadensis. In Ulu Gombak, Malaysia, they were able to distinguish two forms in the field by the more reddish coloration of one but found the color difference vague in specimens kept in the lab or stored in alcohol. A study of males from this site shows differences in the development of the occipital lobes between the red and nonred forms, but when males from the whole range of G. menadensis are included, these differences collapse. In addition, the number of males available for study is too small to assess the variability of their morphological features.

The type of Stictoponera stylata was present in the collection of J. Chapman but apparently became separated from its label during World War II. Specimens from Chapman's collection made their way to the Museum of Comparative Zoology where Brown (1954b) and Chapman determined that the S. stylata type was among the material they were studying. During the course of the present revision, these specimens were not found in the MCZC, but a series of point mounted workers of G. menadensis from Mt. Makiling, collected by Baker, were found in the National Museum of Natural History. Among this series is a worker with an additional label bearing only the number 20408. This number is similar to those found on "MCZ Cotype" labels for type specimens deposited there during that time (e.g., 20419 for the holotype of Gnamptogenys taivanensis). On this evidence the aforementioned specimen is considered the probable holotype of S. stylata and has been labeled as such: "Probable holotype."

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

Description

Worker

Lattke 2004 Gnamptogenys fig 28-30

Lattke (2004) - Metrics (n = 16): HL 1.30-1.55, HW 1.07-1.23, ML 0.61-0.75 , SL 1.13-1.37, ED 0.25-0.31, WL 1.76-2.11 mm. CI 0.77-0.83, SI 1.03-1.15, MI 0.55-0.61, OI 0.24-0.26. Head with broadly convex lateral margins in frontal view, posterior margin straight with laterally protruding occipital lobes, anterior margin of clypeal lamella forms blunt angle, sometimes projecting anterad as narrow lobe; frons rugulose-foveolate with sharp, roughly longitudinal ridges, foveolae with smooth, convex bottoms; frontal lobe with straight lateral margin; clypeus longitudinally strigose; scape varies from very strigulose to mostly smooth; occipital lobe prominent, projecting posteroventrally in lateral view, lamella convex, low, with ends either angular or convex, usually convex; eye situated posteriorly on head, usually less than one ocular diameter from vertex.

Humeral angle lamellate, pronotal ventral margin narrow, anteroventral corner frequently angular, side densely foveolate with fine strigulae on posterior margin; pronotal dorsum densely foveolate with sharp ridges between depressions, median broad groove present on posterior half; promesonotal suture marked as fine line; mesonotum usually with median longitudinal strip of mostly smooth cuticle; anepisterum narrow, rectangular to cuneiform, usually smooth with some foveolae; katepisternum foveolate, with or without strigulae; metapleuron posteroventrally strigose, anterodorsally with narrow strip of mostly smooth or undulate cuticle; propodeum foveolate, propodeal declivity surrounded posterolaterally by ridges forming denticle or low triangular projection, medially with raised, parallel-sided surface that ends before anterior margin, cuticle surrounding raised area usually smooth. Petiolar node dorsally foveolate; with subquadrate to lobe like ventral process in lateral view; postpetiolar dorsum foveolate anterad, foveolae becoming shallower and sparser posterad, laterally densely foveolate anteriorly; postpetiolar sternum transversely strigulose, laterally foveolate to punctate; dorsum of abdominal segment 4 mostly smooth with scattered punctulae; fourth abdominal sternite strigulose-punctate. Fore coxa transversely strigulose in lateral view; fore tarsus opposite strigil with single prominent basal seta, occasionally followed apically by row of slender setae; metacoxal spine usually curved from the base. Dorsum of thorax and abdominal segments 1-4 with scattered erect to subdecumbent hairs. Head, mesosoma, petiole, and gaster ferruginous brown to brown, gaster frequently darker colored than rest of body.

Queen

Lattke (2004) - Metrics (n = 1): HL 1.27, HW 1.03, ML 0.60, SL 1.14, ED 0.21, WL 1.83 mm. CI 0.81, SI 1.11, MI 0.58, OI 0.20. Pronotum densely foveolate, laterally with narrow mostly smooth band along posterior margin, rest of lateral mesosoma densely foveolate; mesoscutum with shallow foveolae, median longitudinal and shallow sulcus present; propodeal dorsum densely foveolate.

Male

Lattke (2004) - Metrics (n = 1): HL 1.09, HW 1.00, ML 0.53, SL 0.25, ED 0.43, WL 2.00 mm. CI 1.09, SI 0.25, MI 0.53, OI 0.43. Frons mostly foveolate, mandibular dorsum mostly smooth with scattered punctae, clypeus mostly smooth with longitudinal undulations and scattered foveolae laterally. Mesonotum mostly rugulose-punctate in lateral view; anepisternum approximately equal in size to katepisternum; mesoscutum foveolate with large intervening smooth areas, propodeum densely foveolate. Petiolar node densely foveolate. Fore coxa mostly smooth in lateral view, slightly colliculate dorsad, with low transverse strigulae apically.

Karyotype

  • 2n = 42 (Malaysia) (Goni et al., 1982; Imai et al., 1983).

References