Myrmelachista joycei Longino 2006

Formicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker face view

worker lateral view

queen face view

queen lateral view

Queen in images above is holotype.

Additional images:

Holotype queen, label (large). Different queen, face view (large). Male, face view (large); abdomen, lateral view (large); genitalia (large). Different male, abdomen, lateral view (large); abdomen, ventral view (large); genitalia (large); pygostyles (large).


Costa Rica, Nicaragua. In Costa Rica it occurs in cloud forest above 1000m, from the Cordillera de Tilarán south to the Cordillera de Talamanca. I have one record of a queen from cloud forest near Matagalpa, Nicaragua.


Diagnosis: Worker with antenna 9-segmented, color red brown. Queen with head black, mandible and clypeus usually smooth and shiny, HW 70.5-1.08mm, CI 87-98, OcI 3-6. Male with digitus elongate, curving, scimitar-shaped.

Worker: Antenna 9-segmented; maxillary palpus 5-segmented but terminal segment elongate, sometimes with partial constriction suggestion partial fusion of terminal two palpomeres; mandible, clypeus, and face smooth and shining; in full face view, side and rear margins of head with sparse to abundant subdecumbent pubescence, sometimes with projecting setae on posterolateral vertex; ventral surface of head with very abundant short subdecumbent pubescence, no erect setae; scape with abundant suberect setae, longer setae about equal to width of scape; hind tibia with abundant appressed to suberect setae, relatively uniform length, about 1/4 to 1/2 width of tibia; typically with dark brown head and gaster, mottled dark and light brown mesosoma, sometimes uniformly dark brown, never strongly bicolored (nanitics may be bicolored).

Measurements: HL 0.556-0.655, HW 0.556-0.670, SL 0.302-0.352, EL 0.114-0.137, CI 100-107 (n=5).

Queen: Antenna 9-segmented; maxillary palpus 6-segmented; dorsal surface of mandible smooth and shining with sparse piligerous puncta or weakly punctatorugose; clypeus and face largely smooth and shining with sparse small piligerous puncta; in full face view side and rear margins of head with abundant short appressed to suberect pubescence, without longer erect setae, sometimes with longer erect setae on posterolateral vertex; ventral surface of head with abundant subdecumbent to suberect setae, these similar to or longer than setae on sides of head; scape with abundant suberect setae, longer setae about equal to width of scape; hind tibia with abundant appressed to suberect setae, relatively uniform length, about 1/4 to 1/2 width of tibia; color largely black, sometimes with some degree of lighter red color on anterior face.

Measurements: HL 0.793-1.124, HW 0.747-1.083, SL 0.395-0.531, EL 0.213-0.269, OW 0.024-0.069, OD 0.176-0.220, CI 87-98 (87 for specimen from northern Nicaragua, 89-98 for Costa Rican material), OI 25-29, OcI 3-6 (n=12).

Male: Antenna 10-segmented; maxillary palpus 6-segmented; pygostyles minute, in the form of weakly sclerotized papillae; basiparamere with elongate lobe; paramere elongate and linear, with parallel sides; cuspis a small, weakly sclerotized narrowly triangular tooth appressed to the inner surface of the paramere, distant from digitus; digitus elongate, curving, scimitar-shaped; apodeme of penial valve curving into dorsal margin at obtuse angle.

Natural History

This species is very abundant in cloud forest. It nests in live branches of canopy trees, with columns extending out in galleries beneath epiphyte mats. It is one of the most common arboreal ants in the Monteverde cloud forest, occurring in a high frequency of tree crowns (Longino 2000) and common in canopy fogging samples (Schonberg et al. 2004). Active colony space occurs in hollow stems near shoot tips, but also extends far back in the centers of live branches, such that workers may be found in narrow chambers deep in the center of relatively thick branches, to 10cm diameter or more. Periodic larger chambers contain dense masses of workers, queens, and brood and may be well-protected deep in solid wood. Clusters of workers and brood also occur beneath epiphytes and in small bits of dead wood. Colonies are large and may occupy an entire tree crown. Large colonies are strongly polygynous, with clusters of physogastric queens scattered throughout the colony space. Pseudococcidae and Coccidae commonly occur in the nests and in the surface galleries beneath epiphytes. Colonies have been found in live branches of Sapium oligoneuron, Vismia, Clusia alata, Cecropia angustifolia (formerly polyphlebia), Ficus, Ocotea austinii, hemiepiphytic Araleaceae, Licaria, and Erythrina. A founding queen was found in a live stem of an orchid.

Literature Cited

Longino, J. T. (2000). The ants of Monteverde. Monteverde: ecology and conservation of a tropical cloud forest. Nadkarni, N. M. and Wheelwright, N. T. New York, New York, Oxford University Press, 132–136.

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

Schonberg, L., Longino, J. T., Nadkarni, N. M., Yanoviak, S. P. and Gering, J. C. (2004). Arboreal Ant Species Richness in primary, secondary forest and pasture habitats of a tropical montane landscape. Biotropica 36, 402–409.

Page author:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA.

Date of this version: 20 March 2006.
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