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Genus Myrcidris

The genus Myrcidris was described from a single species, M. epicharis Ward, originally discovered by Woody Benson, and found to inhabit the live hollow stems of an Amazonian ant-plant in the genus Myrcia (Ward, 1990). A few stray workers of a second, undescribed (but closely related) species were recently collected in Guyana by Ted Schultz. The key features of the workers and queens of Myrcidris are the 11-segmented antennae (with partial fusion of the second and third funicular segments, so that in some views the antenna appears 10-segmented), single proximal tooth on the basal margin of the mandible, four teeth on the masticatory margin of the mandible, non-truncate upper surface of the median clypeal lobe, laterally extended median lobes of the antennal sclerites, and well-developed sulcus on the mesobasitarsus and the metabasitarsus. Males can be recognized by their possession of 13 antennal segments (in all other pseudomyrmecine ants the male antennae are 12-segmented) and by various features of the male terminalia (see Ward, 1990).

In the key below, the following measurements and indices are cited:

HW maximum width of head, including the eyes (in mm)
HL length of head, measured from the anterior extremity of the clypeus to the midpoint of a line drawn across the posterior margin of the head (in mm)
CI cephalic index = HW/HL

Key to species of Myrcidris, based on the worker caste

1a: Larger species, with relatively broad head; HW 0.49-0.61, CI 0.75-0.79 (n = 14); Amazonas, Brazil …. epicharis Ward

1b: Smaller species, with more elongate head; HW 0.39-0.42, CI 0.64-0.66 (n = 3); Guyana …. undescribed species

Frontal view of head of worker (left), queen (center) and male (right) of Myrcidris epicharis.

Literature Cited

Ward, P. S. 1990. The ant subfamily Pseudomyrmecinae (Hymenoptera: Formicidae): generic revision and relationship to other formicids. Syst. Entomol. 15:449-489

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