Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Veracruz lowlands of Mexico through Central America and the West Indies to hylean South America, at least as far south as the Beni River drainage of Bolivia, and on the west slope of the Andes to southern Ecuador (Brown 1978). Costa Rica: wet forest in Atlantic lowlands to 800m elevation.
Combined length of head and closed mandibles less than 1.75mm; petiolar node as seen from the front or rear with apical margin distinctly concave, the 2 free corners forming angles or produced as teeth; second segment of antennal funiculus less than twice as long as broad.
Anochetus are presumably predators, using their snapping mandibles much like their larger relatives, Odontomachus. However, there are few direct observations. "A. mayri is found mostly in forests under stones, in moss on rocks or logs, in rotten twigs on the forest floor, or in larger bodies of rotten wood. The workers and queen feign death, and are difficult to see (Brown 1978)." There appear to be two distinct forms in the Atlantic lowlands of Costa Rica, one of which may be more arboreal (see below).
From Brown 1978:
A. mayri was first proposed in a key, without a proper description, from a specimen from St. Thomas in the West Indies. It was never described in full by Emery, so when Wheeler described the subspecies laeviuscula, he did not know what the "typical" mayri was like. In fact, we still have no clear idea of what the color, sculpture, etc. of the mayri type really are... But we do know that the mayri complex is widespread in the West Indies and shows there wide variation in size, color and sculpture, including samples with predominantly smooth and some with completely striate pronota, as well as intermediates. After prolonged study of this material, I cannot find any way to separate it into two species, or even into reasonably clearcut geographical forms, so I assume that mayri and laeviusculus are synonyms.
On the mainland, the situation is more complex, because the variation is more extensive. The Atlantic lowland forest of Costa Rica, for example, contains a larger, dark brown form (HL 1.05-1.08, HW 0.92-0.94, ML 0.57-0.58, eye L 0.13 mm) with punctulate-striate sculpture weak in the middle of the pronotum, and weakly shining, but still not completely smooth. Sympatric in this area (for instance, at Rio Toro Amarillo, near Guapiles, Limon Prov.) is a smaller (HL 0.93, HW 0.82, ML 0.48, eye L 0.10-0.11 mm) brownish-yellow phenon with completely longitudinally striate pronotum. Whether these forms are conspecific or not cannot be decided without more evidence from this locality, but there are available intermediates among samples from elsewhere in the range...
These two forms appear to be sympatric and distinct at La Selva Biological Station. Additional distinguishing features are that the larger, darker form has the mesopleuron largely smooth, punctate only in the anterodorsal corner. In contrast, the lighter form has the mesopleuron with the upper third punctate (Figure: reduced, original).
The two forms in the mayri complex appear to segregate vertically. The dark form occurs frequently in berlese samples of soil and leaf litter, and in samples of sifted leaf litter from forest floor. In contrast, the light form has not appeared in any Berlese or Winkler samples, including those of Project ALAS, but I have encountered it three times during general collecting: (1) two dealate queens with larvae under a rotting pejibaye palm trunk on ground, (2) workers under loose bark of a rotten log, and (3) a nest under and in a thick humus mat in the crown of a subcanopy Pentaclethra tree.
Anochetus mayri Emery 1884. Syntype worker: Virgin Island, St. Thomas.
Brown, W. L., Jr. 1978. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section B. Genus Anochetus and bibliography. Studia Entomol. 20:549-652.
Emery, C. 1884. Materiali per lo studio della fauna Tunisia raccolti da G. e L. Doria. III. Rassegna delle formiche della Tunisia. Annali del Museo Civico di Storia Naturale di Genova (2)1:373-386.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.firstname.lastname@example.org
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