Tetramorium bicarinatum (Nylander)

Bolton, B., 1979, The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Malagasy region and in the New World., Bulletin of the British Museum (Natural History) Entomology 38, pp. 129-181 : 164-165

Tetramorium bicarinatum (Nylander)

(Figs 39, 43, 47)

Myrmica bicarinata Nylander, 1846: 1061 . Syntype workers, female, U. S. A.: California, 1840 (types lost). Tetramorium bicarinatum (Nylander) ; Mayr, 1862: 740. [For a full statement of the current synonymy of bicarinatum , application of the name and discussion of the species see Bolton, 1977: 94.]

Worker. TL 3.4 - 4.5, HL 0.80 - 1.00, HW 0.68 - 0.86, CI 80 - 87, SL 0.54 - 0.68, SI 75 - 84, PW 0.50 - 0.62, AL 0.94 - 1.20 (114 measured).

Mandibles very finely and densely longitudinally striate; extremely rarely the mandibles appearing finely shagreened. Anterior clypeal margin with a marked median notch or impression. Median portion of clypeus with three longitudinal carinae of about equal strength, a median and one on each side. Sometimes another carina present on each side of the median but these are very feeble by comparison and nearly always incomplete or broken. Frontal carinae strong, running back almost to the occiput and equipped above with a narrow, raised semitranslucent rim or flange. Eyes relatively large, maximum diameter c. 0.19 - 0.24 so that diameter of eye is 0.26 - 0.29 x HW. Pronotal angles sharp in dorsal view. Metanotal groove absent but some specimens with a shallow impression in the alitrunk outline at its approximate position. Propodeal spines in profile strong and acute, moderately long, varying from more or less straight to slightly upcurved along their length. Metapleural lobes elongate-triangular and upcurved. Petiole node in profile roughly rectangular, with parallel or almost parallel anterior and posterior faces and an evenly convex dorsum which meets each face in an angle. The anterodorsal and posterodorsal angles of the node in profile are on a level as the dorsum of the node does not slope upward posteriorly. Dorsum of head with scattered irregular longitudinal rugae with a few cross-meshes but behind the level of the eyes with a strong rugoreticulum (Fig. 47). Ground-sculpture between the rugae superficial and inconspicuous. Dorsum of alitrunk, petiole and postpetiole reticulate-rugose, the sides of the pedicel segments similarly sculptured. Gaster unsculptured for the most part but nearly always with some short, fine, basal costulae on the first tergite. These may be very faint but are only rarely completely absent. All dorsal surfaces with numerous erect or suberect hairs, those projecting from the dorsum of the frontal carinae between the antennal insertions and the occipital corner relatively short (by comparison with other species of the group), shorter than the maximum diameter of the eye. Head, alitrunk, petiole and postpetiole varying from light yellow-brown to bright orange-yellow, the gaster always much darker, deep brown or blackish brown.

T. bicarinatum is a highly successful tramp species which appears to have originated in SE Asia. It is now reasonably common throughout the tropical and subtropical zones of the world except for the Ethiopian region, from which it is unknown. In temperate zones bicarinatum is capable of establishing itself in hothouses, conservatories and other constantly heated buildings.

It is the only member of its group to be found in Madagascar, but in the New World two closely related species also occur as introductions. These are pacificum and insolens , both of which differ from bicarinatum in having the mandibles smooth and shining. In addition to this, the petiole node is very differently shaped in pacificum (compare Figs 43 and 44) and the ant is uniformly dark brown or black in colour. T. insolens also differs in colour from bicarinatum , having the gaster the same colour or lighter than the head and alitrunk, and in addition having relatively much longer hairs on the dorsum of the frontal carinae, which are distinctly longer than the maximum diameter of the eye (compare Figs 39 and 40).

For a full list of material previously examined see Bolton (1977: 96). In this study I have examined material of the Neotropical region from Mexico, Trinidad, Cuba, Puerto Rico, Antigua, Dominican Republic, Barbados, Haiti, Panama, Costa Rica, Honduras, Nicaragua, Venezuela, Colombia, Bolivia, Guiana, Brazil and Peru, which indicates that bicarinatum is fairly well established in the neotropics. Material from North America has been seen from the Bahamas, Florida, New York, Ohio, Wisconsin, Illinois, Georgia, Texas, W. Virginia, California. The majority of this material is deposited in USNM, Washington; MCZ, Cambridge; LACM, Los Angeles; BMNH.