Labidus praedator sedulus (Menozzi 1926): possible cryptic species or synonym.
Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Mexico to Argentina. Type locality Brazil. Costa Rica: wet forest areas throughout.
Worker: color brown; face microsculptured, matte; mesosoma relatively gracile, dorsal face of propodeum as long as or longer than posterior face; ventral margin of petiole flat, lacking anteroventral tooth.
Similar species: spininodis, JTL-001.
This is a widespread and common species throughout the Neotropics. In Costa Rica it can be locally abundant, but seems to be somewhat patchy. I have not encountered it in dry forest areas, but it does occur in both lowland and montane wet forest. On the Barva transect in Braulio Carrillo National Park, it is a relatively rare ant at La Selva but reaches much higher density at 1000-1500m elevation.
Labidus praedator forms massive carpet raids that blanket the ground. In some ways they can be more impressive than Eciton burchellii, because the workers are smaller and more dense, and the ground and low vegetation become almost entirely black with a seething mass of workers. They seem to be mainly subterranean, without surface bivouacs. The large surface raids always seem to emerge spontaneously from the leaf litter or from a hole in the ground. Small segments of columns may be encountered, emerging from one hole and entering another one a few meters away.
I have rarely observed the prey of L. praedator, so I do not know what their dietary preferences are. In one raid I observed a mass of workers harvesting pieces from a fruit on the forest floor, so they may have somewhat generalized scavenging habits, like L. coecus. In cloud forest habitats I have sometimes seen masses of terrestrial isopods rushing up low vegetation and forming clusters on leaf tips in response to a Labidus swarm in the leaf litter below, but I do not know if the Labidus actually prey on the isopods.
Males are occasionally attracted to lights at night, and may also be collected in Malaise traps.
Borgmeier (1955) recognized two subspecies: praedator s. str. and praedator sedulus (Menozzi 1926). The type locality of praedator s. str. is Brazil, of sedulus Colombia. The male of praedator s. str. had the frons relatively flat and the mandibles acuminate; the male of sedulus had the frons more elevated and the tip of the mandible obliquely truncate and somewhat emarginate (Figure). The soldier of praedator s. str. had the rear margin of the head more or less flat, not deeply emarginate; the soldier of sedulus had the rear margin deeply emarginate. The material examined by Borgmeier showed overlapping or interdigitated ranges. He identified workers of praedator s. str. from Mexico, Belize, Guatemala, Nicaragua, Panama, Peru, Guyana, throughout Brazil, Paraguay, and Argentina; and males from Mexico, Bolivia, Brazil, Paraguay, and Argentina. For sedulus, he identified workers from Costa Rica, Panama, and Colombia; and males from Costa Rica, Panama, Colombia, and Bolivia.
The males I have examined from Costa Rica have the emarginate mandibles of sedulus. The degree of emargination of the head of the soldier depends greatly on the size of the soldier, and I do not trust that character without a more quantitative assessment. Until variation is investigated more thoroughly, I prefer to refer to the Costa Rican material as praedator s. str. and to ignore sedulus until it is better defined.
Borgmeier, T. 1955. Die Wanderameisen der neotropischen Region. Studia Entomologica 3:1-720.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. firstname.lastname@example.org
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