Formicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images: dorsal view of worker from La Selva (reduced, original); worker from Corcovado (reduced, original).
Range
Costa Rica: Atlantic and southern Pacific lowlands.
Identification
Minor worker: Propodeum lacking spines or tubercles of any kind; propodeum somewhat box-like, dorsal and lateral faces flat or nearly flat and meeting at an approximate right angle; dorsal face of propodeum subrectangular; first gastral tergite with very dense, long, bright gold appressed pubescence; abundant gold erect setae cover mesosoma and head; erect setae on first gastral tergite relatively long, intermediate between planatus and brettesi; uniformly dark brown to dark red brown; side of mesosoma densely punctate, not shining; mesosomal profile relatively flat (makes nests of leaves sewn together with silk).
Two workers from Corcovado National Park do not have the same mesosomal profile as material from La Selva. The propodeal shape is like brettesi (dorsal face more sloping, meeting posterior face at more obtuse angle), but the strong golden pubescence and pilosity is like La Selva material. Also, the surface sculpture on these two workers is duller than either La Selva textor or brettesi. Image of worker: (reduced, original).
Similar species: JTL-045, senex.
Natural History
This species inhabits mature rainforest canopy, where it builds nests by sewing leaves together with larval silk (Forel 1899, 1905, Wheeler 1915, Schremmer 1979, Holldobler and Wilson 1983). This is one of four Camponotus species I know in Costa Rica that exhibit this behavior (see chartifex, JTL-045, nitidior).
I have only seen the silk nests once. At La Selva Biological Station there is a large foot bridge that crosses the Rio Puerto Viejo. On each side of the river the bridge goes through the crowns of canopy trees growing on the banks of the river. One of these is an Inga, and for a while it contained nests of textor. From the side of the bridge I could see two or three of the nests, each a cluster of leaves and silk about the size of a baseball. This was in the early 1990's, but in recent years (late 1990's) I have not seen them.
The species does not seem very common. The only record of textor in 52 canopy fogging samples at La Selva is one dealate queen, and a worker was collected in one Malaise trap sample. I also collected two workers of textor at Sirena in Corcovado National Park. These two workers were stray workers on tree trunks, not associated with silk nests, and given their differences from La Selva textor (see above) may not be conspecific. In general textor seems to be a low density species in Costa Rica, but may have higher densities elsewhere in the Neotropics.
Wheeler (1915) discussed the Camponotus species that build exposed nests of leaves sewn together with silk and use their larvae as a source of silk. He observed that these species tend to have very weak polymorphism. I also have noted the surprising lack of major workers in textor and JTL-045. There is some variation in worker size, but no large major workers. Members of the subgenus Dendromyrmex exhibit no size variation at all. The workers of subgenus Dendromyrmex do not seem at all closely related to C. textor and JTL-045, suggesting that the construction of silk nests and the weak to absent polymorphism have evolved independently in two different lineages.
Comments
Forel described senex textor based on a Costa Rican collection by Tonduz. It was collected in a silk nest attached to leaves, and the entire nest, with queen, was sent to Forel. The description includes the dense yellow pubescence and abundant long erect pilosity, and I am confident of this determination.
I used to call this species C. senex Smith 1858, and literature reports refer to senex as a species that builds silk nests. However, examination of Alex Wild's images of the type of senex (Click here) suggest senex is not the silk nest builder, but instead a widespread species that nests in dead wood. See senex.
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 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), Schremmer (1979), and Hšlldobler and Wilson (1983).
I have concluded that all the observations of "Camponotus senex" using larvae to make exposed silk nests are of other species that are not senex. I am using the name textor for these, but auricomus should be looked at as a potential older name.
Literature Cited
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.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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