Euprenolepis procera

Witte and Maschwitz (2008) showed that Euprenolepis procera are nomadic mushroom harvesters. This is a unique and previously unknown lifestyle for ants.

Identification
This is the only known polymorphic Euprenolepis species. Majors of Euprenolepis procera superficially resemble Pseudolasius, but can be separated from that genus by the characters given in the genus diagnosis. This species possesses several unique characters other than worker polymorphism. E. procera has especially long scapes, although not as long as in Euprenolepis negrosensis. The eyes of E. procera are more forward toward the midline and lower in the head than observed in other species. The medially emarginated clypeus is most pronounced in E. procera. It is by far the darkest colored species and possesses the thickest, most distinct rugoreticulae covering the body. (Lapolla 2009)

Distribution
Known from Indonesia and Malaysia.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia, New Guinea. Oriental Region: Thailand.

Biology
Witte and Maschwitz (2008) conducted field studies with this species in Malaysian rainforest.

They summarized some of their results in this way "The nest density of E. procera was very high at the study site, with about half of the baits in close vicinity of a mushroom harvester ant colony. Furthermore, a single colony of E. procera had the capacity to harvest several mushrooms during one night. These ants must therefore have a significant impact on fungal fruiting bodies. The foraging activity of E. procera depended on the availability of mushrooms and reduced foraging success over several consecutive days raised a colony’s tendency to migrate. Consequently, the irregular foraging pattern, the opportunistic nesting habits, and the observed migratory lifestyle appear to be adaptations to the challenging food source of fungi......Besides the remarkable biology of E. procera, the mode of gaining nutritional value from low quality fungal material is of future interest. Once retrieved into the nest, fungal material is “conserved” by the ants for many days through special processing which might help to overcome periods of mushroom shortages. The exact mechanism of the food processing is still under investigation."

Details that informed this summary and other results from their study include the following:


 * 44% of the mushroom baits (n=92) placed on the forest floor at night were fed upon by E. procera within the first four hours of bait placement. The average distance from the bait to a nest was 4.5 m. The ants depleted 73% of the mushrooms within these 4 hours.
 * More than 30 out of 80 species of mushrooms were fed upon, including species occurring in association with the root system of the rainforest trees (mycorrhiza).
 * Mushrooms appear to be their primary and almost exclusive source of nutrients:
 * Colonies were rarely observed feeding on anything other than mushrooms.
 * Lab colonies thrived on a mushroom and water diet.
 * Laboratory observations showed that fungal piles brought into the nest were processed by workers, with feeding leading to an expansion of their gasters. Mushroom pieces being used within nests degraded slower than similar pieces left to degrade without intervention by the ants. Larvae were fed by regurgitation from the workers crop rather than directly feeding on the mushrooms.

The ants are nocturnal foragers.

Lizon à l’Allemand et al. (2019) examined competition as a possible explanation for the dietary specialisation found in this species. They note that competition between co-existing species for limited resources is considered a main driving force of niche differentiation, including dietary specialization. Responses to interference competition vary, ranging from combat in dominant species to avoidance in submissive ones. Submissive species often show alternative strategies to avoid competition such as quick and efficient resource exploitation or shifts to less competitive resources. In the present study, we have evaluated the potential role of interference competition as driver of dietary specialisation in the mushroom-harvesting formicine ant Euprenolepis procera (Emery, 1900). This ant harvests a broad spectrum of wild-growing mushroom fruiting bodies – an exceptional diet among ants. We asked whether competition avoidance for more typical ant diets could explain the high degree of dietary specialization in E. procera. In baiting experiments at the Ulu Gombak field station, Malaysia, we first showed that E. procera also utilizes alternative food sources (tuna and honey) demonstrating that mushroom-harvesting is not a hard-wired foraging strategy. In contrast to expectations, E. procera’s competitive ability for these resources was relatively high compared with other ants in the community. In a second experiment, we offered three resources (honey, tuna, mushroom) simultaneously and close to each other in baiting stations. In the absence of other ants, all three resources were exploited at similarly high rates by E. procera workers. However, E. procera avoided foraging on tuna and honey baits when those baits were utilized by other ants. This context-dependent food choice behaviour in E. procera suggests that the exceptional dietary specialization on wild-growing mushrooms represents a case of competition-induced niche differentiation. Finally, we provide new data about the geographic distribution and about variability in seasonal dietary preferences of E. procera.

Colony Attributes
Captured colonies varied in size from 500 - 5000 workers and up to 3 queens. Some larger colonies found emigrating were estimated to contain more than 20,000 individuals.

Nesting appeared to follow what is typically associated with army ants. Nests were opportunistically situated inside preformed cavities and migrations were frequent (n=8 median 4 days, range 1-9 days). Movement may have been triggered by low food resources within their reachable surroundings. Foraging was observed up to 30 m (n=22 range from 4-30) from the nest.

Castes
Polymorphic workers, minors (3.5 - 4.4 mm) are much more common than majors (5.0 - 6.3 mm).

Nomenclature

 *  procera. Prenolepis procera Emery, 1900d: 699, fig. 14 (w.) INDONESIA (Sumatra). LaPolla, 2009: 13 (q.m.). Combination in Prenolepis (Euprenolepis): Emery, 1906b: 134; in Paratrechina (Euprenolepis): Emery, 1925b: 224; in Euprenolepis: Bolton, 1995; 189. Senior synonym of antespectans: LaPolla, 2009: 13.
 * antespectans. Camponotus (Myrmosphincta) antespectans Forel, 1913k: 130, fig. MI (w.) INDONESIA (Sumatra). Combination in Paratrechina (Euprenolepis): Emery, 1925b: 223; in Euprenolepis: Bolton, 1995b: 189. Junior synonym of procera: LaPolla, 2009: 13.

Worker
Lapolla (2009) - Measurements: Majors (n=4): TL: 5.08–6.25; HW: 1.35–1.61; HL: 1.43–1.62; SL: 1.8–2.03; WL: 1.9–2.22; GL: 1.75–2.41. Indices: CI: 94–101; SI: 126–139.

Minors (n=7): TL: 3.53–4.39; HW: 0.82–1.05; HL: 0.94–1.14; SL: 1.4–1.67; WL: 1.49–1.67; GL: 1.1–1.57. Indices: CI: 87–95; SI: 153–178.

Major. Head dark reddish-brown, roughly heart-shaped; head distinctly broader than long. Antennal funiculi slightly lighter in color. Head with scattered erect setae and a sparse layer of pubescence; cuticular surface strongly rugoreticulate. Posterior margin strongly emarginate medially. Scapes surpass posterior margin by about length of first three funicular segments; scapes with erect setae and sparse pubescence. Anterior clypeal margin strongly emarginate. Mesosoma dark reddish-brown, legs becoming lighter distally; cuticular surface rugoreticulate. Mesosomal dorsum with scattered erect setae of varying lengths on the posterior pronotum and mesonotum; sparse pubescence scattered across mesosoma, with denser patches on the anterior pronotum, metanotal area and propodeum. Pronotum rises at about 45° toward mesonotum; mesonotum and mesonotal area flat; propodeum dorsum rounded, dome-like; declivity steep. Petiole triangular with posterior face longer than anterior face; gaster dark reddish-brown, covered in erect setae with a layer of pubescence; cuticular surface rugoreticulate.

Minor. As in major, with modifications expected for caste. Scapes long, surpassing posterior margin by about length of the first four funicular segments. The legs of minor workers are slightly lighter than found in majors.

Queen
Lapolla (2009) - Measurements (n=1): TL: 6.3; HW: 1.1; HL: 1.0; SL: 1.6; WL: 2.5; GL: 2.8. Indices: CI: 110; SI: 145.

As in worker, with modifications expected for caste and the following differences: Overall color similar to worker castes, but mottled dark brown, with lighter brown patches especially on head and mesosoma. Entire body covered in a dense layer of pubescence; short erect setae cover head, mesosoma notum, legs and gaster. Erect setae most abundant on gaster, becoming denser posteriorly.

Male
Lapolla (2009) - Measurements (n=2): TL: 4.54–4.85; HW: 0.70–0.75; HL: 0.86–0.89; SL: 1.54–1.63; WL: 1.77–1.81; GL: 1.88–2.18. Indices: CI: 81–84; SI: 218–219.

Overall color brown to brownish-yellow, lighter brown on legs and funiculi; head longer than broad. Cuticular surface shiny, covered in a dense layer of pubescence. Scapes long, surpassing posterior margin by about length of first four funicular segments; scapes with scattered erect setae and a dense layer of pubescence. Clypeus broad, with anterior margin emarginated. Mandible with a basal angle and a distinct apical tooth that curves in toward body midline. Mesosoma enlarged to accommodate flight muscles; covered in a layer of pubescence, with erect setae dorsally and on legs. Pronotum small and distinctly collar-like; mesonotum offset from pronotum at sulcus; mesonotum rises sharply above height of pronotum, giving pronotum a shelf-like appearance in lateral view. Mesonotum flat dorsally with scattered erect setae; propodeum indistinct from remainder of mesosoma, with declivity shallow, gently sloping toward petiole. Petiole triangular, upright, with posterior face only slightly longer than anterior face. Gaster with a dense layer of pubescence and scattered erect setae, becoming denser posteriorly toward terminalia; terminalia especially setose. Parameres roughly triangular, turning slightly mesad posteriorly; long setae extend off of parameres. Cuspi small and tubular, reaching digiti dorsally; digiti anvil-shaped, directed ventrally; digiti visible in lateral view. Volsellar lobes with large bulbous extensions; appressed setae cover surface. Penis valves with apodeme projecting dorsally; in lateral view the valves extend dorsally.

Type Material
Lapolla (2009) :

Syntype workers, INDONESIA: Sumatra, Si Rembé, Panherang Pisang. (type depository unknown, not in ) [not examined].

Camponotus (Myrmocsphincta) antespectans Holotype worker, INDONESIA: Sumatra (v. Buttel) [examined].

References based on Global Ant Biodiversity Informatics

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