Acropyga manuense

Acropyga manuense
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Formicinae
Tribe:	Plagiolepidini
Genus:	Acropyga
Species group:	smithii
Species:	A. manuense
Binomial name
Acropyga manuense LaPolla & Schneider, 2023

This species, only known from the Peruvian Amazon, is associated with the mealybug Neochavesia podexuta (LaPolla & Schneider, 2023), a trophobiont.

Photo Gallery

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  LaPolla & Schneider (2023), Figures 4–6. Acropyga manuense, worker USNMENT01130435 (holotype). 4, lateral view. 5, full-face view. 6, dorsal view.
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  LaPolla & Schneider (2023), Figures 7, 8. Acropyga manuense, queen USNMENT01130436. 7, lateral view. 8, full-face view.
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  LaPolla & Schneider (2023), Figures 9–12. Acropyga manuense, male USNMENT01130437. 9, lateral view. 10, full-face view. 11, ventral view of genitalia. 12, dorsal view of genitalia.
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  LaPolla & Schneider (2023), Figures 1–3. Dissected penial sclerites of various species in ectal view. Scale bar: A. fuhrmanni and A. smithii = 0.03 mm; A. manuense = 0.05 mm.

Identification

LaPolla & Schneider (2023) - A member of the Acropyga smithii species group. The workers of A. manuense are similar in overall appearance to both Acropyga fuhrmanni and Acropyga smithii with all three possessing 8 antennal segments (although A. smithii workers can occasionally be found with as few as 7 segments) and 4 mandibular teeth. One of the most obvious ways A. manuense workers differ from both A. fuhrmanni and A. smithii workers is in mesosomal pubescence. In A. manuense workers possess thick pubescence that extends down the lateral portions of the pronotum and onto the mesopleuron. In A. fuhrmanni and A. smithii pubescence is very sparse to lacking on the lateral portions of the pronotum and the mesopleuron.

Several measurements will also allow for separation of the three species. The smallest of the three species is A. smithii with a head width and length less than 0.4 mm, whereas both A. fuhrmanni and A. manuense have head widths and lengths greater than 0.4 mm. The scape length in A. smithii is less than 0.27 mm, while it is greater than 0.3 mm in both A. fuhrmanni and A. manuense. The small size of A. smithii makes it fairly easy to distinguish from both A. fuhrmanni and A. manuense. Workers of A. fuhrmanni and A. manuense possesses different eye sizes with a relative eye length index between 12–15 in A. fuhrmanni and between 6–11 in A. manuense (Fig. 13). The cephalic index is also instructive with A. fuhrmanni generally having a value over 100 with A. manuense less than 100.

The most striking differences between A. fuhrmanni, A. smithii and A. manuense are found in males. The mandibles of the three species’ males differ in the number and size of teeth, with A. manuense possessing three distinct equally sized teeth. Both A. fuhrmanni and A. smithii only have two teeth: a prominent apical tooth and a much smaller tooth at the basal angle. There are several genitalic differences between the three species such as each possessing uniquely shaped penial sclerites (Figs 1–3). The digitus is very distinctive within A. manuense, being ventrally directed, elongated and coming to a prominent point (Figs 9, 11). The elongated, pointed structure of the digitus is unique among all Acropyga species.

Keys including this Species

• Key to New World Acropyga Workers

Distribution

Known only from the type locality.

Latitudinal Distribution Pattern

Latitudinal Range: -13.1° to -13.1°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: LaPolla, 2023

Distribution based on Regional Taxon Lists

Neotropical Region: Peru (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

Expand Explore Overview of Acropyga biology  Little is known about Acropyga manuense. Until further studies reveal more about this species we can infer that its natural history and biology should be similar to other Acropyga. LaPolla published a worldwide revision of the Acropyga in 2004 and the following synopsis is based on this excellent treatment of the genus. In overall appearance Acropyga are small, robust, yellowish ants possessing a thin, easily collapsible cuticle. The species generally appear rather similar to each other morphologically. In some species workers and queens display an unusual range of phenotypic variation. Antennal segment number, for example, can vary within and between species. Even a single specimen may posses antennae with a different number of antennal segments and workers in numerous species possess one more antennal segment than conspecific males. The small eyes, reduced antennae segmentation, lightly pigmented cuticle, and hairs covering the cuticle of Acropyga species are suggestive of a completely subterranean existence. Species also display photophobic behavior (Weber, 1944; LaPolla et al., 2002). Acropyga can survive in a wide range of habitats, from deserts to rainforests, though they do not seem able to survive in regions where temperatures below freezing persist for several months at a time. Some species, such as Acropyga pallida and Acropyga silvestrii for example, are found within a very wide range of habitats. Undoubtedly, the Acropyga lifestyle of existing below the surface buffers them against extremes of the outside environment. Acropyga nests are found in leaf litter, under stones, in rotten wood (lying on or near the soil surface) and in the soil. Observations of nests of various species show the nests are large, consisting of at least several thousand individuals. The nest structure is diffuse with apparently no central nesting location (LaPolla et al., 2002). Tunnels and indistinct chambers stretch out over large areas through the nesting medium. Polygyny has been suggested for several species. The origins of polygyny remains uncertain, but two routes are suggested based on field observations. Biinzli (1935) found both the occurrence of pleometrosis (founding of a colony by multiple queens) and the acquisition of young queens by established colonies in Acropyga exsanguis. All Acropyga are thought to be hypogaeic (living entirely underground), surviving primarily by "tending" mealybugs (Hemiptera: Pseudococcidae) on underground roots for their exudate (sometimes referred to as "honeydew") (Weber, 1944; Williams, 1998). This mutually beneficial relationship is called trophobiosis (Holldobler and Wilson, 1990). Acropyga species are all believed to be obligate coccidophiles (dependent on their tended mealybugs for survival). The strength of this trophophitic relationship is clarified by a number of observations. Queens of eleven species have been observed emerging from their nests prior to their mating flight with a mealybug held in their mandibles (Biinzli, 1935; Wheeler, 1935b; Brown, 1945; Eberhard, 1978; Prins, 1982; Buschinger et al., 1987; Williams, 1998; Johnson et al., 2001). The mealybug that each queen carries presumably serves as a "seed individual" from which a new generation of mealybugs will be started in the newly founded ant colony (Weber, 1944; Williams, 1998). This behavior is called trophophoresy (LaPolla et al. 2002) with queens exhibiting this behavior said to be trophophoretic. The mealybugs utilized by Acropyga belong to the subfamily Rhizoecinae, and it is likely that the mealybugs are not able to survive independently of the ants (Williams, 1998). LaPolla et al. (2002) observed that Acropyga epedana keeps mealybugs with their brood. When a nest in captivity was starved, workers refused a variety of food items presented to them, suggestiving that the ants are completely dependent on the mealybugs as a food source. Fossil evidence suggests that the trophobiotic behavior ofAcropyga ants is an ancient one. Johnson et al. (2001) reported that Acropyga queens were discovered in Dominican amber, either holding a mealybug or with a mealybug nearby in the amber matrix. The amber was dated to the Miocene and is at least 15-20 million years old. ‎

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• manuense. Acropyga manuense LaPolla & Schneider, 2023: 5, figs. 3-12 (w.q.m.) PERU.

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

Description

Worker

(N = 8). HW: 0.432–0.489; HL: 0.46–0.531; EL: 0.031–0.057; ML: 0.467–0.583; PW: 0.277–0.329; PFL: 0.326–0.413; HL+ML: 0.927–1.09.

N = 10. Uniformly yellow; covered in a dense layer of pubescence including lateral portions of pronotum and mesopleuron; scattered erect setae across body. Head slightly longer than wide (CI: 90–99); posterior margin slightly concave medially; posterolateral corners rounded with ca. 6 erect setae found along margin; eyes small with uneven pigmentation (REL: 6–11); 8-segmented, incrassate antennae; scapes short of posterior margin by about ¼ to ½ length of pedicel (SI: 71–83); scapes with dense layer of pubescence and scattered erect setae across its length. Clypeus narrow (width in holotype = 0.113 mm) and medially convex. Mandibles with 4 distinct teeth; apical teeth are the longest; teeth 2 and 3 are about equal in size and basal tooth is slightly smaller than teeth 2 and 3; a slight diastema exists between tooth 3 and the basal teeth. In lateral view, mesosoma profile of pronotum steeply rising toward mesonotum (ca. 45° angle if a line is drawn parallel to mesosomal venter). Posterior portion of pronotum and remainder of mesosomal notum with scattered erect setae of varying heights. Highest portion of mesonotum slightly higher than propodeum. Metanotal area distinct with length in holotype = 0.061 mm. Dorsal face of propodeum flat with length in holotype = 0.122 mm; declivitous face steep (ca. 75° angle). Petiole thick and erect with rounded apex; last ¼ of petiole surpasses the most dorsal portion of the propodeal spiracle. Gaster typical of Acropyga with thick layer of pubescence and scattered erect setae.

Queen

N =3. HW: 0.524–0.59; HL:0.55–0.59; EL: 0.147–0.188; ML: 0.844–1.03; PW: 0.531–0.606; PFL: 0.428–0.454; HL+ML: 1.4–1.62.

N = 4. As in worker with modifications expected for caste and with the following differences: CI: 95–100; SI: 78–87; REL: 26–32.

Male

N =3. HW: 0.389–0.399; HL: 0.36–0.4; EL: 0.128–0.155; ML: 0.663–0.692; PW: 0.465–0.494; PFL: 0.412–0.451; HL+ML: 1.04–1.08.

N = 4. Head yellowish-brown, excluding mandibles and funicular segments which are yellow; remainder of body yellow. Head about as long as wide (CI: 99–108); posterior margin slightly rounded; medially with three prominent ocelli just anterior to posterior margin; posterolateral corners rounded with an indistinct angle and 2–3 erect setae. Compound eyes large, surpassing head margin in full-frontal view (REL: 34–40). 9-segmented incrassate antennae; scapes surpass posterior margin by about length of antennal pedicel (SI: 93–97); scapes covered with dense pubescence and widely scattered short erect setae. Clypeus medially convex (clypeal width in paratype USNMENT01130437 = 0.08 mm long); mandible with three teeth, large apical tooth and two smaller teeth at the basal angle; on some mandibles the two smaller teeth appear to have fused at the basal angle rendering the mandible 2-toothed. Mesosoma covered with dense pubescence and scattered short erect setae on mesoscutum and mesoscutellum. Pronotum small and collar-like with overarching large, rounded mesonotum. Mesoscutellum slightly higher than mesoscutellum in lateral view. Propodeum lower than mesonotum with no separation into dorsal and declivitous faces; propodeum flat (paratype USNMENT01130437 = 0.212 mm long) with a slight slope toward petiole. Petiole thick and erect just surpassing the lowest portion of the propodeum in lateral view. Gaster typical of male Acropyga with thick layer of pubescence and scattered erect setae. Gonopods in lateral view tapered to a rounded apex (paratype USNMENT01130437 gonopod length = 0.216 mm long); in dorsal view gonopods medially expanded. Cuspi tubular (paratype USNMENT01130437 = 0.094 mm long); where cuspi meet digiti several peg-like teeth span the surface; several setae extend off of cuspi apex as well; digiti tubular before a distinct right angle bending ventrally where they meet the cuspi; ventral facing portion of digiti taper toward apex becoming needle-like (paratype USNMENT01130437 = 0.108 mm long); apex of digiti visible beyond ventral margin of gonopod in lateral view. Penial sclerites elongate (Fig. 3); ventral margin curves from apex through rounded posterior region; along rounded section of penial sclerites margin dentate; apodeme located medially on anterior end of penial sclerites; apex of penial sclerites bend toward gonopods.

Type Material

• Holotype: Peru • worker; Madre de Dios, Las Cruces, Manu Paradise Lodge, nest behind lodge, in soil around small rotting branches; 13.055°S, 71.544°W; 31.v.2019; J.S. LaPolla and S.A. Schneider leg.; USNMENT01130435 (UNMSM).
• Paratypes: Peru • same data as holotype; 9 paratype workers: USNMENT01130438 (USNM), USNMENT01130439 (USNM), USNMENT01130450 (USNM), USNMENT01130451 (USNM), USNMENT01130452 (USNM), USNMENT01130453 (USNM), USNMENT01130454 (USNM), USNMENT01130465 (USNM), USNMENT01130483 (USNM); paratype queens: USNMENT01130436 (USNM), USNMENT01130467 (USNM), USNMENT01130468 (USNM), USNMENT01130480 (USNM); paratype males: USNMENT01130437 (USNM), USNMENT01130466 (USNM), USNMENT01130481 (USNM), USNMENT01130482 (USNM).

Etymology

The epithet is a noun in apposition, referring to its type location near Manu National Park, Peru.

References

• LaPolla, J.S., Schneider, S.A. 2023. Trophobiosis between a new species of Acropyga (Hymenoptera, Formicidae) and new Neochavesia (Hemiptera, Xenococcidae) from Peru, and establishment of the Acropyga smithii species-group. ZooKeys 1154, 1–16 (doi:10.3897/zookeys.1154.97578).