Myrmelachista mexicana Wheeler,

Longino, J. T., 2006, A taxonomic review of the genus Myrmelachista (Hymenoptera: Formicidae) in Costa Rica., Zootaxa 1141, pp. 1-54: 39-40

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Myrmelachista mexicana Wheeler


Myrmelachista mexicana Wheeler  HNS 

Myrmelachista mexicana Wheeler  HNS  1934:200. Syntype workers, queen, males: Mexico, Veracruz, Mirador (Skwarra #296), in hollow twigs [ MCZC, USNM] (USNM syntype worker examined)  . Combination in M. (Hincksidris)  HNS  : Kempf, 1972:149.


Worker with antenna 10-segmented, face shiny, HW less than 0.5mm.


Antenna 10-segmented; maxillary palpus 6-segmented; mandible, clypeus, and face smooth and shining; in full face view, sides of head with sparse, short, appressed pubescence, no erect setae; rear margin of head with longer erect setae; ventral surface of head with very sparse, very short appressed pubescence, no erect setae; hind tibia with abundant appressed to suberect setae, pilosity short, about 1/4 width of tibia; mesosoma strongly constricted at metanotal groove, hourglass-shaped; dorsal face of propodeum with faint to pronounced reticulate sculpture; petiole in side view with low, rounded node, short anterior peduncle and long posterior peduncle; bicolored, with light red brown head and mesosoma, dark brown gaster, or grading to more uniformly dark red brown coloration. Also see description of Wheeler (1934).

Measurements: HL 0.438-0.471, HW 0.389-0.423, SL 0.256-0.292, EL 0.093-0.100, CI 87-90 (n=5).


Similar to worker in meristic characters, patterns of sculpture, pilosity, coloration. Labrum short, bilobed. Also see description of Wheeler (1934).

Measurements: HL 0.570-0.599, HW 0.483-0.484, SL 0.285-0.297, EL 0.175-0.180, OW 0.032, OD 0.147-0.156, CI 81-85, OI 36-37, OcI 5-6 (n=2).


See description of Wheeler (1934). Wheeler’s figure of male genitalia show similarities to zeledoni  HNS  , with blunt basiparamere lobe and paramere, and strongly upturned penial valve (suggesting that apodeme meets dorsal margin at right angle, like zeledoni  HNS  ). The volsella is not visible in the illustration, suggesting it is short and downturned, like zeledoni  HNS  . Pygostyles are not shown, suggesting they are absent or minute.


Mexico, Costa Rica, Panama. In Costa Rica it is known from La Selva Biological Station and Arenal National Park.


The types of M. mexicana  HNS  were collected in hollow twigs in southern Mexico. A dealate queen at USNM was intercepted by Brownsville quarantine in an orchid stem from the Canal Zone in Panama. At La Selva Biological Station and on the Barva transect in Braulio Carrillo National Park it has been collected in several Project ALAS Malaise and canopy fogging samples, from 50 to 500m elevation.

At La Selva I found a colony in a small dead stem in the crown of a recently felled Carapa guianensis  . The relict tree was somewhat isolated in low second growth vegetation, and there were abundant vines over the crown, mainly Marcgraviaceae. The colony was polygynous, with multiple dealate queens. In the field, the tiny workers looked like small Solenopsis  HNS  or Monomorium floricola  HNS  .

Material Examined

COSTA RICA, Alajuela: Par. Nac. Arenal, La Peninsula , 10°27’N, 84°45’W, 600m (J. S. Noyes)GoogleMaps  ; Heredia: La Selva Biological Station , 10°26’N, 84°01’W, 50m (ALAS)GoogleMaps  ; same data (J. Longino, 3 collections)GoogleMaps  ; MEXICO, Veracruz: Mirador , 19°13’N, 96°51’W (E. Skwarra) [ USNM]GoogleMaps  ; PANAMA, Canal Zone: Canal Zone (Brownsville Quarantine) [ USNM]  .


USA, Massachusetts, Cambridge, Harvard University, Museum of Comparative Zoology


USA, Washington D.C., National Museum of Natural History, [formerly, United States National Museum]