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Mexico to southern Brazil. Costa Rica: Atlantic and southern Pacific lowlands, Central Valley.
This species is very common in lowland wet forest habitats. It can occur in both mature forest and highly disturbed areas. For example, workers are very common in canopy fogging samples from mature forest at La Selva Biological Station, yet I have also found them on the landscaping around the Juan Santa Maria airport near San Jose. Foragers are diurnal.
Nests occur in highly insolated areas such as upper forest canopy, open scrubby or second growth vegetation, roadsides, and agricultural land. The species is an opportunistic cavity nester. Nests are in dead branches, ranging from narrow vine stems to relatively large branches. In surveys of Cecropia trees, I often find nests in internodes of saplings, or in mature trees abandoned by Azteca, or in peripheral portions of trees that have a dominant Azteca colony elsewhere in the crown.
This species is morphologically and behaviorly very similar to C. planatus. The two species seem to differ in the degree of habitat disturbance they prefer. This species is relatively more common in mature forest habitats, while C. planatus dominates in open areas subject to higher disturbance rates.
Through an early misidentification by Forel, it has been thought that senex builds silk nests. There is no mention of the nest of senex in Smith's original description nor in Mayr's (1878) redescription. Forel (1879) reviewed the Camponotus species related to senex, and identified a collection from Cordoba, Mexico, as senex. The Mexican collection was from a "paper nest among branches," and Forel noted the similarity of the nest of "senex" with the silk nests of chartifex and nitidior (subgenus Dendromyrmex). Forel (1899) described the subspecies textor, based on material that Tonduz collected in Costa Rica, from a carton nest on leaves. Forel later (1905) identified Brazilian material as senex and reported Gšldi's observations that the larvae are used to spin silk for the nest. Wheeler (1915) reviewed use of larval silk for nest construction by ants, perpetuating the association of senex with carton nests. This was followed by Wheeler and Wheeler (1953), Hšlldobler and Wilson (1983), and Schremmer (1979).
Alex Wild provided an image of the type of senex (Click here) and it is clearly not the Costa Rican species that builds silk nests. All the observations of "Camponotus senex" using larvae to make exposed silk nests are of other species that are not senex. See textor.
Forel, A. 1879. ƒtudes myrmŽcologiques en 1879 (deuxime partie [1re partie en 1878]). Bull. Soc. Vaudoise Sci. Nat. 16:53-128.
Forel, A. 1899. Biologia Centrali-Americana; or, contributions to the knowledge of the fauna and flora of Mexico and Central America. Insecta. Hymenoptera. 3 (Formicidae). London. 169 pp.
Forel, A. 1905. Einige biologische Beobachtungen des Herrn Prof. Dr. E. Gšldi an brasilianischen Ameisen. Biol. Centralbl. 25:170-181.
Holldobler, B., and E. O. Wilson. 1983. The evolution of communal nest-weaving in ants. American Scientist 71:490-499.
Mayr, G. 1878 ("1877"). Formiciden gesammelt in Brasilien von Professor Trail. Verh. K-K. Zool.-Bot. Ges. Wien 27:867-878.
Schremmer, F. 1979. Das Nest der neotropischen Weberameise Camponotus (Myrmobrachys) senex Smith (Hymenoptera, Formicidae). Zoologischer Anzeiger 203:273-282.
Smith, F. 1858. Catalogue of hymenopterous insects in the collection of the British Museum. Part VI. Formicidae. London: British Museum, 216 pp.
Wheeler, G. C., Wheeler, J. 1953. The ant larvae of the subfamily Formicinae. Ann. Entomol. Soc. Am. 46:126-171.
Wheeler, W. M. 1915. On the presence and absence of cocoons among ants, the nest-spinning habits of the larvae and the significance of black cocoons among certain Australian species. Ann. Entomol. Soc. Am. 8:323-342.
Das mir aus Brasilien vom Mus. Caes, vorliegende Exemplar stimmt in allen Eigenschaften mit Smith's Beschreibung ueberein, ausser darin, dass es oben eine etwas ausgerandete Schuppe hat, dass die Geissel, mit Ausnahme des ersten Gliedes, schwarz ist, ferner dass der Kopf, Thorax, und Hinterleib ziemlich reichlich abstehend behaart sind. Smith's Worte: „ the node of the peduncle ovate " beruhen jedenfalls auf einer Irrung; Smith wollte wohl statt node: scale schreiben.
Found most commonly in these habitats: 11 times found in Entre SHO y SSE, 7 times found in CES 400, 13 times found in montane wet forest, 5 times found in SURA 850M, 4 times found in SSO 350m, 7 times found in lowland rainforest, 2 times found in wet forest edge, 3 times found in wet forest, 1 times found in 2nd growth wet forest, 3 times found in Pentaclethra, ...
Found most commonly in these microhabitats: 6 times beating vegetation, 6 times copa de árbol, 1 times nest in dead stem, 3 times Malaise trap, 1 times canopy fogging sample, 3 times strays, 1 times Roadside veg., nests in several adjacent dead sticks., 1 times nest in dead stick, 1 times nest in dead branch Ficus, 1 times In 9mm dia vertical dead branch, 1 times beating veg., ...
Collected most commonly using these methods: 76 times Fogging, 18 times Malaise, 10 times search, 7 times Beating, 2 times flight intercept trap, 1 times Malaise trap, 2 times Sweeping, 1 times Search & Berles, 1 times yellow pan trap.
Elevations: collected from 5 - 2250 meters, 127 meters average