Trachymyrmex smithi

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Trachymyrmex smithi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Trachymyrmex
Species: T. smithi
Binomial name
Trachymyrmex smithi
Buren, 1944

Trachymyrmex smithi casent0105871 profile 1.jpg

Trachymyrmex smithi casent0105871 dorsal 1.jpg

Specimen labels

Synonyms

Identification

Trachymyrmex smithi might be confused with Mycetomoellerius jamaicensis due to its large size and dark coloration, but the species are allopatric; M. jamaicensis is only known from southwest Florida, the Florida Keys, and the Caribbean, whereas T. smithi occurs in the deserts of western Texas, New Mexico, and the State of Coahuila in northern Mexico. In addition, the frontal and preocular carina of T. smithi do not form a well developed antennal scrobe that extends back to the preoccipital margin as in M. jamaicensis, and the frontal lobes are triangular in T. smithi, not rounded, as in M. jamacensis. (Rabeling et al. 2007)

Keys including this Species

Distribution

Trachymyrmex smithi is a Chihuahuan Desert species that occurs in southwest Texas, south-central New Mexico, and the Mexican states of Chihuahua and Coahuila. (Rabeling et al. 2007)

Latitudinal Distribution Pattern

Latitudinal Range: 34.16409° to 11.55254°.

   
North
Temperate 		North
Subtropical 		Tropical South
Subtropical 		South
Temperate

Distribution based on Regional Taxon Lists

Nearctic Region: United States.
Neotropical Region: Mexico (type locality).

Distribution based on AntMaps

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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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Habitat

Inhabits creosote bush bajadas (alluvial fans), mesquite/Yucca grassland playas (dry lakebeds) and mesquite coppice dune habitats at elevations of 1100–1500 m. (Rabeling et al. 2007)

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. ‎

From Rabeling et al. (2007): Nests are often in the shade of creosote bush or Mormon tea (Ephedra trifurca). Older nests may have large nest mounds (~30 cm diameter) with conspicuous middens consisting of dried leaves and exhausted fungus substrate. The subterranean nests of T. smithi are the largest of all Trachymyrmex species occurring in the US. Older nests consist of more than 20–30 chambers (Johnson et al. 2006; Rabeling & Mueller, unpublished data) of which 50–60% contain fungus gardens in the summer. Near El Paso, Texas, the fungus gardens are nourished with entire mesquite leaflets (Johnson et al. 2006; Rabeling, unpublished data), and resemble the fragile fungus gardens of grass-cutting Acromyrmex species in South America. Colonies can be very populous; Johnson et al. (2006) report up to 786 workers and 6 dealate queens in one nest, and Schuhmacher and Whitford (1974) estimate 1250 workers for one colony based on mark-recapture experiments. Colony activity and the number of fungus gardens decrease from November through May (Schuhmacher & Whitford 1976). Two nests, which we partially excavated during winter, had 26 chambers per colony, reaching down to 180 and 130 cm depth, respectively. None of the chambers contained a fungus garden in December, suggesting that T. smithi moves its gardens to deeper layers in winter. During springtime the excavation of two adjacent colonies showed, that in April the ants already moved the fungus garden to shallower nest chambers. Numerous fungus gardens were encountered hanging from the chambers’ ceilings in 25–130 cm depth. From the partially excavated winter colonies, 212 and 362 workers were collected (Rabeling & Mueller, unpublished data). Trachymyrmex smithi forages mostly at night during the summer months, to avoid soil temperatures exceeding 50°C during the day (Whitford 1978).

Castes

Worker

Images from AntWeb

Trachymyrmex smithi casent0172997 head 1.jpgTrachymyrmex smithi casent0172997 profile 1.jpgTrachymyrmex smithi casent0172997 dorsal 1.jpgTrachymyrmex smithi casent0172997 label 1.jpg
Paratype of Trachymyrmex smithi. Worker. Specimen code casent0172997. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by MCZ, Cambridge, MA, USA.

Nomenclature

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

  • smithi. Trachymyrmex smithi Buren, 1944b: 5 (w.) MEXICO (Coahuila).
    • Type-material: holotype worker, 58 paratype workers.
    • Type-locality: holotype Mexico: Coahuila, desert nr La Rosa, 5.xi.1942 and 8.xi.1942 (E. Buren).
    • [Note: Buren does not specify the collection date of the holotype.]
    • Type-depositories: LACM (holotype); AMNH, LACM, USNM (paratypes).
    • Rabeling, et al. 2007: 21 (q.m.).
    • Combination in Trachymyrmex: Solomon, Rabeling, et al. 2019: 948.
    • Status as species: Bolton, 1995b: 421; Mackay & Mackay, 2002: 246; Rabeling, et al. 2007: 20 (redescription); Sánchez-Peña, et al. 2017: 88 (in key).
    • Senior synonym of neomexicanus: Rabeling, et al. 2007: 20.
    • Distribution: Mexico, U.S.A.
  • neomexicanus. Trachymyrmex smithi subsp. neomexicanus Cole, 1952a: 159, fig. 1 (w.) U.S.A. (New Mexico).
    • Type-material: holotype worker, 202 paratype workers.
    • Type-locality: holotype U.S.A.: New Mexico, 6 mi. N Las Cruces, east side Highway US 85, 15.ix.1951, no. N-341 (A.C. Cole); paratypes: 180 workers with same data, 22 workers with same data but no. A-232.
    • Type-depositories: LACM (holotype); AMNH, DRIR, FMNH, LACM, MCZC, USNM (paratypes).
    • Cole, 1953g: 300 (q.m.).
    • Subspecies of smithi: Cole, 1953g: 300; Cole, 1955b: 49; Smith, M.R. 1958c: 138; Hunt & Snelling, 1975: 22; Smith, D.R. 1979: 1412; Dlussky, 1981a: 48; Bolton, 1995b: 421; Mackay & Mackay, 2002: 246.
    • Junior synonym of smithi: Rabeling, et al. 2007: 20.

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

from Rabeling et al. (2007): Buren (1944) described T. smithi from Mexico (La Rosa, Coahuila) and Cole (1952) later based the subspecies T. smithi neomexicanus on workers from the United States (Las Cruces, New Mexico). Cole separated neomexicanus from smithi because it possessed larger and less tuberculate spines, a more concave posterior margin of the postpetiole, larger body size, darker color, and more abundant gray “granulation” on the integument. For a Trachymyrmex, T. smithi workers show considerable size variation and all characters, except color and the presence of granulation, vary proportionally to size. The morphological differences cited by Cole for neomexicanus fall well within the range of variation shown by this widely distributed species. Likewise, black, reddish-brown and intermediate color morphs are distributed over the species entire range, including the type locality (C. Rabeling personal observation). Molecular evidence also supports our contention that in T. smithi we are dealing with a single variable species. The short branch lengths in the molecular phylogenetic analysis (see below) show that the sequence diversity is minimal and similar for both smithi and neomexicanus. The more abundant gray granulation of neomexicanus mentioned by Cole (1952) is most likely caused by actinomycete bacteria of the genus Pseudonocardia (Cafaro & Currie 2005), which grow on the ant’s exoskeleton. Actinomycete load on the worker’s body surface varies among individuals of the same nest and is affected by worker age, characteristic activity (foraging versus garden-tending), or the health of the fungus garden. This coating is therefore of no taxonomic importance. To remove the sometimes confusing actinomycete coating, specimens can be washed with acidic acid (vinegar).

Description

Worker

Diagnosis from Rabeling et al. (2007): HL 0.94–1.25, HW 1.0–1.375, CI 100–111, SL 0.86–1.19, SI 84–89, ML 1.25–1.69. A large, dark colored species. Head trapezoidal, almost cordate; always broader than long (HW > HL) even in the smallest workers, widest at midpoint between the eye and the posterior corner, and strongly tapering anteriorly. Posterior margin of head moderately concave, more so in larger workers. Antennal scapes short, surpassing the posterior corner of the head by its maximum diameter or less. In full-face view, frontal carinae extending almost to the posterior corners, but weakening before they reach the vertex. Preocular carinae variably developed, traversing approximately half the distance between eye and frontal carina, never touching the frontal carinae. Antennal scrobes weakly developed. In full-face view, frontal lobes small, broadly triangular, usually asymmetrical, with anterior side longer than the posterior. In dorsal view, anterolateral promesonotal tooth thick, sharply pointed, projecting horizontally, not vertically. Anterior median promesonotal tubercles short, vertical, toothlike in frontal or posterior view. Propodeal teeth strongly divergent, spinelike and longer than the distance separating their bases. Vertex of head and gaster strongly tuberculate, remainder of body moderately tuberculate, tuberculi small, tubercular setae weakly to strongly recurved; tuberculi on sides of mesosoma miniscule and sparse. Texture of entire body surface coarse, sandpaperlike. Trachymyrmex smithi displays considerable color variation, ranging from grayish black or blackish brown to rarely dark red or reddish-brown.

Queen

Diagnosis from Rabeling et al. (2007): HL 1.2, HW 1.35–1.4, CI 113–114, SL 1.05–1.1, SI 78–79, ML 1.9–2.0. As in worker diagnosis but with typical caste-specific mesosomal morphology related to wing-bearing and head with small ocelli. Dorsolateral pronotal teeth well developed, tuberculate and sharply triangulate in dorsal view. Ventrolateral pronotal teeth short, triangular, not tuberculate and pointed. Mesoscutum longitudinally rugulose, not tuberculate. Pronotal sides, mesopleura and propodeum with only a few minute tuberculi, if any. Setae abundant, short, straight and suberect. Dorsum of mesosoma, petiole, postpetiole and gaster distinctly bicolored.

Male

Diagnosis from Rabeling et al. (2007): HL 0.81–0.84, HW 0.84–0.87, CI 100–107, SL 0.93–0.99, SI 107–118, ML 1.9–2.05. A large male with relatively long appendages and antennal scapes. Preocular carina a distinctive vertical ridge as it passes the eye and curves towards the midline, remaining strongly developed until the posteriormost portion of the “scrobe.” Ocelli moderately large, slightly elevated above the remainder of the head in side view. Dorsolateral pronotal teeth very short, indistinct, or absent. Ventrolateral pronotal teeth short, triangular. Mesoscutum with weakly reticulate longitudunal rugluae, interrugal spaces granulate. First gastric tergite minutely tuberculate, with numerous, short, decumbent or suberect recurved setae.

Type Material

From Rabeling et al. (2007):

Holotype worker Los Angeles County Museum of Natural History, Paratype workers American Museum of Natural History, Los Angeles County Museum of Natural History, National Museum of Natural History; Holotype worker Los Angeles County Museum of Natural History, Paratype workers American Museum of Natural History, Los Angeles County Museum of Natural History, Museum of Comparative Zoology, National Museum of Natural History. Examined.

To our great surprise we encountered two holotypes of T. smithi Buren; one deposited in the LACM and the other in the USNM collection. Most likely, the USNM specimen was mislabeled and actually represents a paratype, because Buren (1944, p. 6) stated that the single holotype would remain in his personal collection and paratypes would be deposited in the National Museum and his personal collection. Since the LACM accessioned the W. F. Buren collection in 1983, we here designate the holotype of T. smithi as the specimen deposited at the LACM.

Type Locality Information

La Rosa, Coahuila, Mexico; 6 mi N Las Cruces along Hwy US 85, New Mexico, U.S.A. (Rabeling et al. 2007).

Etymology

Buren (1944) named this species after Marion R. Smith, myrmecologist and curator of Hymenoptera at the National Museum of Natural History in Washington, DC for many years during the mid twentieth century. (Rabeling et al. 2007).

References

References based on Global Ant Biodiversity Informatics

  • Bestelmeyer B. T., and J. A. Wiens. 2001. Local and regional-scale responses of ant diversity to a semiarid biome transition. Ecography 24: 381-392.
  • Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
  • Klingenberg, C. and C.R.F. Brandao. 2005. The type specimens of fungus growing ants, Attini (Hymenoptera, Formicidae, Myrmicinae) deposited in the Museu de Zoologia da Universidade de Sao Paulo, Brazil. Papeis Avulsos de Zoologia 45(4):41-50
  • Mackay W. P., and E. E. Mackay. 2002. The ants of New Mexico (Hymenoptera: Formicidae). Lewiston, New York: Edwin Mellen Press, 400 pp.
  • McDonald D. L., D. R. Hoffpauir, and J. L. Cook. 2016. Survey yields seven new Texas county records and documents further spread of Red Imported Fire Ant, Solenopsis invicta Buren. Southwestern Entomologist, 41(4): 913-920.
  • Moody J. V., and O. F. Francke. 1982. The Ants (Hymenoptera, Formicidae) of Western Texas Part 1: Subfamily Myrmicinae. Graduate Studies Texas Tech University 27: 80 pp.
  • Nash M. S., W. G. Whitford, J. Van Zee, and K. M. Havstad. 2000. Ant (Hymenoptera: Formicidae) responses to environmental stressors in the Northern Chihuahuan Desert. Environ. Entomol, 29(2): 200-206.
  • O'Keefe S. T., J. L. Cook, T. Dudek, D. F. Wunneburger, M. D. Guzman, R. N. Coulson, and S. B. Vinson. 2000. The Distribution of Texas Ants. The Southwestern Entomologist 22: 1-92.
  • Rabeling C., S. P. Cover, R. A. Johnson, and U. G. Mueller. 2007. A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae). Zootaxa 1664: 1-53
  • Solomon S. E., C. Rabeling, J. Sosa-Calvo, C. Lopes, A. Rodrigues, H. L. Vasconcelos, M. Bacci, U. G. Mueller, and T. R. Schultz. 2019. The molecular phylogenetics of Trachymyrmex Forel ants and their fungal cultivars provide insights into the origin and coevolutionary history of ‘higher-attine’ ant agriculture. Systematic Entomology 44: 939–956.
  • Van Pelt, A. 1983. Ants of the Chisos Mountains, Texas (Hymenoptera: Formicidae) . Southwestern Naturalist 28:137-142.
  • Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
  • Wheeler, G.C. and J. Wheeler. 1985. A checklist of Texas ants. Prairie Naturalist 17:49-64.
  • Whitford W. G. 1978. Structure and seasonal activity of Chihuahua desert ant communities. Insectes Sociaux 25(1): 79-88.
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