Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Image catalog (click here).
Range
Widespread in Neotropics from southern Mexico to Argentina.
Identification
This is a member of the crinosa complex and may not always be distinguishable from crinosa and torosa. See under crinosa for further discussion. In Costa Rica rochai always has the fourth abdominal tergite completely devoid of erect setae, and the anteroventral petiolar process is long and sharp. Costa Rican material also lacks a differentiated dorsal face of the propodeum, but material from central and southern South America develops a stronger propodeal suture, thus approaching the condition in other crinosa group material. Also, southern material often has one to five erect setae on the anterolateral portions of the fourth abdominal tergite.
Description of worker
Differing from crinosa and torosa by the following combination of characters: dorsal and posterior face of propodeum in nearly the same plane, such that the propodeal suture appears very shallow with no posterior wall, the propodeum forming a single declivity from the propodeal suture to the petiolar insertion (very large workers have a short dorsal face that drops to propodeal suture); promesonotum strongly arched, not flattened; anteroventral petiolar tooth long, sharply acute, triangular to spine-like; fourth abdominal tergite completely lacking erect setae.
Measurements:
HL 0.851, 0.519, 1.139; HW 0.915, 0.535, 1.238; HC 0.905, 0.509, 1.207; SL 0.559, 0.375, 0.681; EL 0.198, 0.114, 0.257; A11L 0.247; A11W 0.123; A10L 0.110; A10W 0.104; A09L 0.062; A09W 0.078; A08L 0.045; A08W 0.060; WL 0.913, 0.500, 1.259; SPL 0.098, 0.069, 0.158; PTH 0.200, 0.121, 0.265; PTL 0.271, 0.158, 0.407; PTW 0.279, 0.166, 0.343; PPL 0.232, 0.128, 0.286; PPW 0.262, 0.167, 0.352; CI 108, 103, 109; OI 23, 22, 23; SI 66, 72, 60; PTHI 74, 77, 65; PTWI 103, 105, 84; PPI 113, 130, 123; SPI 11, 14, 13; ACI 0.57.
Description of Queen (Costa Rica)
A normal queen (dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum) with general shape, sculpture, and pilosity characters of the worker.
Natural History
Crematogaster rochai has a biology very similar to crinosa and torosa. It occurs primarily in open, seasonally dry areas, highly disturbed areas, pasture edges, and beach margins. It occasionally occurs in mangroves, although crinosa is the more common mangrove inhabitant. I have never collected it in rainforest areas.
Nests are large, polydomous, and distributed in a wide variety of plant cavities. Dead branches and knots in living trees are most often used. In Guanacaste Province in Costa Rica colonies may occupy ant acacias and may invade acacias occupied by Pseudomyrmex. I have seen workers distributed in small chambers scattered in the corky bark of Tabebuia trees (Bignoniaceae) and Erythrina trees (Fabaceae). Workers often construct small carton baffles to restrict nest entrances and small carton pavilions that shelter Homoptera on surrounding vegetation.
Foraging is primarily diurnal. Workers are generalized scavengers and they frequently visit extrafloral nectaries. Often columns of workers move between nests.
I often find cockroach egg cases scattered in the nest chambers of C. rochai, at a much higher density than in the environment generally. The nature of the relationship between cockroaches and the crinosa group would be worth investigation.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Date of this version: 4 March 2003.
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