Sericomyrmex opacus

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Sericomyrmex opacus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Sericomyrmex
Species: S. opacus
Binomial name
Sericomyrmex opacus
Mayr, 1865

Sericomyrmex opacus F43c.jpg

Sericomyrmex opacus F43e.jpg

Synonyms

A fungus growing ant with a wide distribution. Most collections have been from forested areas. The biology of Sericomyrmex opacus has not been studied, general details about the biology of the genus are given here.

Identification

Ješovnik & Schultz (2017) - Small species; mandible smooth, glossy; posterior cephalic corner smoothly rounded; frontal lobe rectangular; eye small, often with at least partial white layer; mesosomal tubercles low, reduced; first gastral tergite with lateral carinae weakly developed, dorsal carinae absent.

The species most similar to S. opacus are Sericomyrmex parvulus, Sericomyrmex saramama, and, in Central America, smooth-mandibled populations of Sericomyrmex amabilis. Typical amabilis can be distinguished from opacus by their completely striate mandibles, triangular frontal lobes, and larger size. The distinction between opacus and smooth-mandibled amabilis is less obvious, but the frontal lobes, head shape, and size are still good indicators. An ameliorating factor for this difficulty is that, when sympatric, amabilis and opacus are very distinct; we have not encountered the smooth-mandibled amabilis variant sympatric with opacus, which might indicate character displacement. The queen of S. opacus can easily be separated from that of the sympatric S. amabilis by its smaller size, smooth mandibles (striate in amabilis), and usually less conspicuous notauli on the scutum. The main characters separating S. opacus from saramama are the shape of the frontal lobes (triangular in saramama) and the white layer over the eyes (absent in saramama). The S. saramama queen can easily be separated from the opacus queen by its striate mandibles (smooth in opacus).

S. parvulus can be distinguished from the typical opacus by having smaller, narrower, triangular frontal lobes; smaller overall size; and shorter frontal carinae, often fading well before reaching the posterior cephalic corners. Separating non-typical representatives of opacus, which may also have reduced frontal lobes, from parvulus is difficult. Also, it is very difficult to separate queens of opacus and parvulus. The parvulus queen is slightly smaller and lacks the faint supraocular carinae; however, these carinae are absent in some opacus queens as well. The region of overlap of the known distributions of these two species is limited, so geographic origin can aid in species identification.

S. opacus is morphologically variable across its geographic range. This variation is correlated with patterns in the molecular phylogeny (Suppl. material 1) as well as with geography. The most pronounced variation within opacus occurs in the shape of the frontal lobes and in the eyes. The typical S. opacus has rectangular frontal lobes and the eyes covered with a thin white layer. There are occasional, rare individuals with smaller, almost triangular lobes and eyes lacking the white layer. These rare, odd specimens are also smaller in size, so these atypical character states could be correlated with size (e.g., in nanitic workers). The specimens from the opacus 3 population all have eyes lacking the white layer and the frontal lobes are often (but not always) more triangular than rectangular.

Keys including this Species

Distribution

Brazil, Central America, Colombia, Mexico.

Latitudinal Distribution Pattern

Latitudinal Range: 22.3889° to -22.908°.

 
North
Temperate
North
Subtropical
Tropical South
Subtropical
South
Temperate

Distribution based on Regional Taxon Lists

Neotropical Region: Brazil (type locality), Colombia (type locality), Guatemala (type locality), Honduras, Mexico (type locality), Panama.

Distribution based on AntMaps

AntMapLegend.png

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.
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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.
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Biology

Explore-icon.png Explore Fungus Growing 
For additional details see Fungus growing ants.

A handful of ant species (approx. 275 out of the known 15,000 species) have developed the ability to cultivate fungus within their nests. In most species the fungus is used as the sole food source for the larvae and is an important resource for the adults as well. Additionally, in a limited number of cases, the fungus is used to construct part of the nest structure but is not as a food source.

These fungus-feeding species are limited to North and South America, extending from the pine barrens of New Jersey, United States, in the north (Trachymyrmex septentrionalis) to the cold deserts in Argentina in the south (several species of Acromyrmex). Species that use fungi in nest construction are known from Europe and Africa (a few species in the genera Crematogaster, Lasius).


The details of fungal cultivation are rich and complex. First, a wide variety of materials are used as substrate for fungus cultivating. The so-called lower genera include species that prefer dead vegetation, seeds, flowers, fruits, insect corpses, and feces, which are collected in the vicinity of their nests. The higher genera include non leaf-cutting species that collect mostly fallen leaflets, fruit, and flowers, as well as the leafcutters that collect fresh leaves from shrubs and trees. Second, while the majority of fungi that are farmed by fungus-feeding ants belong to the family Lepiotaceae, mostly the genera Leucoagaricus and Leucocoprinus, other fungi are also involved. Some species utilise fungi in the family Tricholomataceae while a few others cultivate yeast. The fungi used by the higher genera no longer produce spores. Their fungi produce nutritious and swollen hyphal tips (gongylidia) that grow in bundles called staphylae, to specifically feed the ants. Finally, colony size varies tremendously among these ants. Lower taxa mostly live in inconspicuous nests with 100–1000 individuals and relatively small fungus gardens. Higher taxa, in contrast, live in colonies made of 5–10 million ants that live and work within hundreds of interconnected fungus-bearing chambers in huge subterranean nests. Some colonies are so large, they can be seen from satellite photos, measuring up to 600 m3.

Based on these habits, and taking phylogenetic information into consideration, these ants can be divided into six biologically distinct agricultural systems (with a list of genera involved in each category):

Nest Construction

A limited number of species that use fungi in the construction of their nests.

Lower Agriculture

Practiced by species in the majority of fungus-feeding genera, including those thought to retain more primitive features, which cultivate a wide range of fungal species in the tribe Leucocoprineae.

Coral Fungus Agriculture

Practiced by species in the Apterostigma pilosum species-group, which cultivate fungi within the Pterulaceae.

Yeast Agriculture

Practiced by species within the Cyphomyrmex rimosus species-group, which cultivate a distinct clade of leucocoprineaceous fungi derived from the lower attine fungi.

Generalized Higher Agriculture

Practiced by species in several genera of non-leaf-cutting "higher attine" ants, which cultivate a distinct clade of leucocoprineaceous fungi separately derived from the lower attine fungi.

Leaf-Cutter Agriculture

A subdivision of higher attine agriculture practiced by species within several ecologically dominant genera, which cultivate a single highly derived species of higher attine fungus.

Note that the farming habits of Mycetagroicus (4 species) are unknown. Also, while species of Pseudoatta (2 species) are closely related to the fungus-feeding genus Acromyrmex, they are social parasites, living in the nests of their hosts and are not actively involved in fungus growing. ‎

Castes

Figure 43bdf.
Figure 44.

Jesovnik and Schultz 2017. Figure 43bdf. S. opacus worker without a white layer over the eyes (USNMENT01125118) (b, d, f). Figure 44. S. opacus worker (USNMENT01125331), SEM images. a Head, full-face view b mandibles c mesosoma and metasoma, lateral view d eye.

Figure 45.
Figure 46.

Jesovnik and Schultz 2017. Figure 45. S. opacus queen and male; head, lateral profile, and dorsal view. Queen (USNMENT00305214) (a, c, e) Male (USNMENT01125314) (b, d, f). Figure 46. S. opacus larva (USNMENT01125317), SEM images. a Lateral view b ventral view c head, frontolateral view d head and thorax, frontolateral view e mouthparts f anal setae.

Worker

Images from AntWeb

Sericomyrmex diego casent0904988 h 1 high.jpgSericomyrmex diego casent0904988 p 1 high.jpgSericomyrmex diego casent0904988 d 1 high.jpgSericomyrmex diego casent0904988 l 1 high.jpg
Syntype of Sericomyrmex diegoWorker. Specimen code casent0904988. Photographer Will Ericson, uploaded by California Academy of Sciences. Owned by MSNG, Genoa, Italy.

Queen

Images from AntWeb

Sericomyrmex opacus casent0909371 p 2 high.jpg
Syntype of Sericomyrmex opacus muelleriQueen (alate/dealate). Specimen code casent0909371. Photographer Will Ericson, uploaded by California Academy of Sciences. Owned by MHNG, Geneva, Switzerland.

Nomenclature

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

  • opacus. Sericomyrmex opacus Mayr, 1865: 84, pl. 3, fig. 22a-c (q.) Brazil.
    • Type-material: holotype queen.
    • Type-locality: Brazil: (no further data).
    • Type-depository: NHMW.
    • [Note: Ješovnik & Schultz, 2017a: 71, suggest the following modifications:
    • Type-material: lectotype worker, 2 paralectotype workers.
    • Type-locality: Mexico: Veracruz, Córdoba (E. Norton).
    • Type-depositories: NHMW (lectotype); NHMW, USNM (paralectotypes).
    • In their discussion Ješovnik & Schultz, 2017a: 78, argue for Mexico as type-locality, and workers as type-material, but Mayr mentions only Brazil, and only a solitary queen is described and figured.]
    • Mayr, 1866a: 506 (m.); Emery, 1894c: 223 (w.); Wheeler, W.M. 1916c: 11 (w.); Ješovnik & Schultz, 2017a: 75 (l.).
    • Status as species: Mayr, 1866a: 506; Dalla Torre, 1893: 150; Emery, 1894c: 223; Forel, 1895b: 138; Wheeler, W.M. 1905b: 130; Forel, 1912e: 191 (in key); Wheeler, W.M. 1916c: 11 (in key); Emery, 1924d: 339; Borgmeier, 1927c: 128; Kempf, 1972a: 229; Bolton, 1995b: 382; Ješovnik & Schultz, 2017a: 71 (redescription); Fernández & Serna, 2019: 874.
    • Senior synonym of aztecus: Ješovnik & Schultz, 2017a: 72.
    • Senior synonym of diego: Ješovnik & Schultz, 2017a: 72.
    • Senior synonym of zacapanus: Ješovnik & Schultz, 2017a: 72.
    • Distribution: Brazil, Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Nicaragua, Panama.
  • aztecus. Sericomyrmex aztecus Forel, 1885a: 363 (w.) MEXICO (Veracruz).
    • Type-material: syntype workers (number not stated).
    • Type-locality: Mexico: Orizaba (de Saussure coll.).
    • Type-depositories: MHNG, MSNG, NHMW.
    • Status as species: Dalla Torre, 1893: 150; Forel, 1899c: 37; Forel, 1912e: 192 (in key); Wheeler, W.M. 1916c: 11 (in key); Emery, 1924d: 339; Wheeler, W.M. 1934g: 178; Kempf, 1972a: 229; Bolton, 1995b: 382; Branstetter & Sáenz, 2012: 261.
    • Junior synonym of opacus: Ješovnik & Schultz, 2017a: 72.
  • diego. Sericomyrmex diego Forel, 1912e: 192 (w.m.) COLOMBIA.
    • Type-material: syntype workers, syntype males (numbers not stated).
    • Type-locality: Colombia: Sierra Nevada de Santa Marta, Don Diego, 3.iii.1896 (A. Forel).
    • Type-depositories: BMNH, MHNG, MSNG, USNM.
    • Status as species: Wheeler, W.M. 1916c: 11 (in key); Emery, 1924d: 339; Kempf, 1972a: 229; Bolton, 1995b: 382.
    • Junior synonym of opacus: Ješovnik & Schultz, 2017a: 72.
  • zacapanus. Sericomyrmex zacapanus Wheeler, W.M. 1925a: 54 (w.) GUATEMALA.
    • Type-material: syntype workers (number not stated, “numerous specimens”).
    • Type-locality: Guatemala: Zacapa, 15.xii.1911 (W.M. Wheeler).
    • Type-depositories: MCZC, NHRS.
    • Status as species: Kempf, 1972a: 230; Bolton, 1995b: 382; Branstetter & Sáenz, 2012: 261.
    • Junior synonym of opacus: Ješovnik & Schultz, 2017a: 72.

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

Description

Ješovnik & Schultz (2017):

Worker

(lectotype): HWe 0.8–1 (0.93) HW 0.8–1 (0.95) HW1 0.78–1 (0.84) HW2 0.88–1.13 (0.96) HW3 0.54–0.74 (0.62) IFW1 0.54–0.73 (0.64) IFW2 0.16–0.28 (0.24) HL1 0.82–1 (0.9) HL2 0.6–0.9 (0.82) SL 0.58–1.08 (0.62) EL 0.12–0.18 (0.15) Om 6–10 (8) WL 0.99–1.3 (1.23) PL 0.2–0.33 (0.21) PPL 0.15–0.25 (0.18) GL 0.78–1 (0.87) HFL 0.68–1.02 (0.93) PW 0.50–0.72 (0.63) CI 95–106 (103) FLI 62–78 (69) SI 65–78 (67) OI 13–19 (16) CEI 5–19 (9) [N=68]

Pilosity. Pubescence dense, often lighter than integument, appressed to decumbent. Hairs curved, darker in color at base, yellow to gray, appressed to suberect, mostly decumbent.

Head. In full-face view almost equally broad and long (CI=100 ± 3), posterior corner smoothly rounded, posterior cephalic emargination relatively shallow (CEI=9 ± 2), gradually impressed. Vertexal impression and frontal tumuli faint. Mandibles with 7–8 teeth, dorsally smooth and glossy, finely transversely striate only along masticatory margin. Eye medium-sized (OI =16 ± 1), flat to slightly convex, 6–10 ommatidia across largest diameter, with (Figure 43a, 44d) or without (Figure 43b) thin white layer. Frontal lobe wide (FLI=70 ± 3), rarely triangular, mostly rectangular to trapeziform, posterior margin as long, or almost as long, as medial. Frontal carina usually incomplete, fading before reaching posterior cephalic corner. Antennal scape relatively short, never reaching posterior cephalic corner (SI=71 ± 2).

Mesosoma. Mesosomal tubercles small, low and obtuse. Propodeal carinae low and feeble, sometimes serrate, sometimes reduced to just posterodorsal denticles.

Metasoma. Petiole with two low, reduced denticles; postpetiole with two faint, short carina dorsally. First gastral tergite with lateral carinae weakly developed, dorsal carinae absent.

Queen

HWe 1.02–1.16 HW 1.05–1.20 HW1 1.10–1.25 HW2 1.20–1.30 HW3 0.72–0.85 IFW1 0.76–0.85 IFW2 0.24–0.33 HL1 1.09–1.12 HL2 0.98–1.00 SL 0.74–0.78 EL 0.20–0.24 Om 15–17 EW 0.08–0.10 WL 1.58–1.80 PL 0.34–0.48 PPL 0.24–0.28 GL 1.50–1.64 HFL 0.99–1.28 PW 0.90–0.96 FWg 4.85–5.17 HWg 3.60–3.64 CI 93–106 FLI 71–76 SI 64–73 OI 18–22 [N=6]

Head. Mandible with 7–8 teeth, dorsally glossy and smooth, finely transversely striate only along masticatory margin. Preocular carina fading posterior to eye, 1–3 isolated, short, thin, supraocular carinae sometimes present, never reaching posterior cephalic corner. Eye large (OI=20 ± 1), convex, 15–17 ommatidia across largest diameter. Frontal lobe as in worker, antennal scape not reaching posterior cephalic corner.

Mesosoma. Lateral pronotal tubercles low and obtuse. Scutum in dorsal view with notauli and median mesoscutal line reduced, parapsidal lines thin. Scutellum small and short, with posterior notch shallow to absent and with median impression sometimes separating scutellum in two lateral halves. Propodeal carinae low, each with low posterodorsal denticle.

Metasoma. Petiole with two dorsal and two lateral low and obtuse denticles, best seen in frontodorsal view. Postpetiole with two short, low carinae dorsally and two low denticles laterally. First gastral tergite with lateral carinae well developed, dorsal carinae absent, anteromedian groove visible.

Male

HWe 0.66–0.74 HW 0.46–0.58 IFW1 0.20–0.27 IFW2 0.13–0.18 HL1 0.53–0.61 SL 0.49–0.62 EL 0.22– 0.28 Om 19–28 EW 0.09–0.14 WL 1.20–1.44 PL 0.27–0.38 PPL 0.16–0.22 GL 0.96–1.12 HFL 1.20–1.50 PW 0.50–0.80 IOD 0.36–0.50 FWg 3.48–4.10 HWg 2.20–2.84 CI 115–125 FLI 30–38 SI 71–88 OI 29–39 [N=7]

Head in full-face view longer than broad (CI=121 ± 4). Eye large (OI=34 ± 3), convex, 19–28 ommatidia across largest diameter. Preocular carina fading posterior to eye, medially curved before fading. Notauli and mesoscutal line faint, parapsidal lines thin, groove between axillae smooth, sometimes weakly transversely costate. Propodeum without denticles or carinae. Petiole and postpetiole with lateral denticles very reduced, dorsal denticles absent.

Larva

Approximately eight setae on each side of dorsal and lateral body surfaces (i.e., approximately 16 total). Supra-antennal setae absent. Four genal setae on each side. Mandibular apical tooth undivided. Labial denticles not visible. First thoracic segment ventrally with multiple multidentate spinules, arranged in transverse rows. Numbers of ventral hairs: six on each thoracic segment, eight on the abdomen (not including anal setae). Single pair of sensilliform setae anterior to anal opening.

Type Material

Lectotype worker (here designated): (“Brazil”)* Mexico, Veracruz, Córdoba, [18.8808, -96.9272], E. Norton (Naturhistorisches Museum Wien, Vienna: 1w, CASENT0915956) Paralectotypes: Same data as lectotype: (NHMW: 1w, CASENT0915955) (National Museum of Natural History: 1w, USNM00924096).

The original description of S. opacus by G. L. Mayr in 1865, which is also the original description of the genus Sericomyrmex, lists “Brasilien” as the type locality. Based on the route of the Novara-Expedition, which is the expedition from which Mayr’s specimens supposedly originated, the Brazilian type locality is most likely Rio de Janiero (Mayr, 1865). However, the locality labels of the type specimens (CASENT0915955, CASENT0915956, USNMENT00924096) of Sericomyrmex opacus that we studied indicate “Mexico, Cordoba,” and “Norton” as the collector. The labels look original when compared to the labels of other Mayr type specimens, both in terms of handwriting and in resemblance to the labels of other specimens collected by Norton. Indeed, Mayr described other species based on specimens collected by E. Norton in Mexico, so he clearly had access to Norton’s Mexican material. Importantly, the type specimen of S. opacus is identical to the type specimen of Sericomyrmex aztecus, a Mexican species described by Forel (1885), which in turn is identical to numerous specimens collected in Mexico and elsewhere in Central America. S. aztecus is the name most commonly applied to such specimens. Given these facts, the most likely explanation is that the locality of the type specimen of S. opacus (“Brasilien”) given in the original description is incorrect and that the locality labels affixed to the syntype specimens are correct. The alternative explanation is that the published locality is instead correct, the specimen labels are incorrect, and that the type specimen of S. opacus originated in Brazil. We judge this alternative to be highly unlikely, because S. opacus (under which we have synonymized S. aztecus, Sericomyrmex diego, and Sericomyrmex zacapanus) does not occur anywhere near Rio de Janeiro.

References

References based on Global Ant Biodiversity Informatics

  • Ahuatzin D. A., E. J. Corro, A. Aguirre Jaimes, J. E. Valenzuela Gonzalez, R. Machado Feitosa, M. Cezar Ribeiro, J. Carlos Lopez Acosta, R. Coates, W. Dattilo. 2019. Forest cover drives leaf litter ant diversity in primary rainforest remnants within human-modified tropical landscapes. Biodiversity and Conservation 28(5): 1091-1107.
  • Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
  • Escalante-Jimenez A. L., and M. Vasquez-Bolanos. 2014. The ants collection (Hymenoptera: Formicidae) of the Laboratorio de Invertebrados, Facultad de Biología, Universidad Michoacana de San Nicolás de Hidalgo. Entomología Mexicana, 1: 1057– 1062.
  • Fernandes, P.R. XXXX. Los hormigas del suelo en Mexico: Diversidad, distribucion e importancia (Hymenoptera: Formicidae).
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  • Jesovnik A., J. Chaul, and T. Schultz. 2018. Natural history and nest architecture of the fungus-farming ant genus Sericomyrmex (Hymenoptera: Formicidae). Myrmecological News 26: 65-80.
  • Jesovnik A., and T. R. Schultz. 2017. Revision of the fungus-farming ant genus Sericomyrmex Mayr (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 670:1-109.
  • Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
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  • Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
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  • Vasquez-Bolanos M. 2011. Checklist of the ants (Hymenoptera: Formicidae) from Mexico. Dugesiana 18(1): 95-133.
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  • Wheeler W. M. 1905. The ants of the Bahamas, with a list of the known West Indian species. Bulletin of the American Museum of Natural History 21: 79-135.