Fischer et al. (2020) found 13 unusual species, which they call the Pheidole lucida group (for the first of its two described species, Pheidole lucida, Pheidole oculata being the other), all of which are associated with other Pheidole species in Madagascar. Although the full biology of these species is not yet known, multiple lines of evidence suggest that they are inquilines (residing inside the nest of another species), and likely social parasites. First, they were frequently observed and collected as part of a nest series of other Pheidole species (i.e., the putative hosts). Second, they have a suite of morphological traits that are typically observed in other inquiline species. The minor worker caste has reduced mandibles and loss of cuticular pigmentation, whereas the queens show modifications found in many other inquiline species that are often referred to as part of a ‘‘parasitic syndrome’’ (e.g., rounded head shape, elongated antennae, broadened postpetiole, etc. (Wilson, 1971; Wilson, 1984)). Third, the major worker subcaste, a hallmark of the genus and present in all 1,000+ non-parasitic Pheidole species, is entirely absent in the P. lucida group. In this genus, the partial loss of the worker caste is a strong indication of a socially parasitic lifestyle, where reproductive allocation to the worker caste is often reduced or lost entirely (Buschinger, 2009; Wilson, 1971; Wilson, 1984; Hoelldobler & Wilson, 1990; Maschwitz et al., 2000; Sumner et al., 2003). Only one of the 13 inquiline species (an undescribed species, Pheidole gf010) seems to be entirely workerless, with the queen itself showing a very reduced, worker-like morphology. Sumner et al. (2003) suggested that workers of incipient social parasites (inquilines) may help the parasitic queen suppress host reproduction and redirect host resources toward the production of parasite queens and males. We refer to this group as ‘‘social parasites’’ because of the evidence above but, without direct observation, the strength of this parasitism in the P. lucida group is uncertain and we cannot rule out weak or even no costs to the host (i.e., commensalism). However, the important point for the following study is that if the workers in the P. lucida group are symbiotic with the host colonies, we should expect their phenotypes to be subject to scrutiny by the host workers in everyday social interactions.
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
Check data from AntWeb
X-ray micro-CT scan 3D model of Pheidole oculata (worker) prepared by the Economo lab at OIST.
The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.
- oculata. Aphaenogaster oculata Emery, 1899f: 276 (q.) MADAGASCAR. Combination in Parapheidole: Emery, 1915d: 68; in Pheidole: Smith, D.R. 1979: 1366.
- Brown, W. L., Jr. 1973b. A comparison of the Hylean and Congo-West African rain forest ant faunas. Pp. 161-185 in: Meggers, B. J., Ayensu, E. S., Duckworth, W. D. (eds.) Tropical forest ecosystems in Africa and South America: a comparative review. Washington, D.C.: Smithsonian Institution Press, viii + 350 pp. (Parapheidole synonymy)
- Buschinger, A. (2009). Social parasitism among ants: a review (Hymenoptera: Formicidae). Myrmecol. News 12, 219–235.
- Emery, C. 1899e. Formiche di Madagascar raccolte dal Sig. A. Mocquerys nei pressi della Baia di Antongil (1897-1898). Bull. Soc. Entomol. Ital. 31: 263-290 (page 276, queen described)
- Emery, C. 1915k. Definizione del genere Aphaenogaster e partizione di esso in sottogeneri. Parapheidole e Novomessor nn. gg. Rend. Sess. R. Accad. Sci. Ist. Bologna Cl. Sci. Fis. (n.s.) 19: 67-75 (page 68, Combination in Parapheidole)
- Fischer, G., Friedman, N.R., Huang, J.-P., Narula, N., Knowles, L.L., Fisher, B.L., Mikheyev, A.S., Economo, E.P. 2020. Socially parasitic ants evolve a mosaic of host-matching and parasitic morphological traits. Current Biology 30, 3639–3646.e4 (doi:10.1016/j.cub.2020.06.078).
- Hoelldobler, B., and Wilson, E.O. (1990). The Ants (Harvard University Press).
- Maschwitz, U.; Dorow, W. H. O.; Buschinger, A.; Kalytta, G. 2000. Social parasitism involving ants of different subfamilies: Polyrhachis lama (Formicinae) an obligatory inquiline of Diacamma sp. (Ponerinae) in Java. Insectes Soc. 47: 27-35.
- Peeters, C., Keller, R.A., Khalife, A., Fischer, G., Katzke, J., Blanke, A., Economo, E.P. 2020. The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour. Frontiers in Zoology 17, 33. (doi:10.1186/s12983-020-00375-9).
- Smith, D. R. 1979. Superfamily Formicoidea. Pp. 1323-1467 in: Krombein, K. V., Hurd, P. D., Smith, D. R., Burks, B. D. (eds.) Catalog of Hymenoptera in America north of Mexico. Volume 2. Apocrita (Aculeata). Washington, D.C.: Smithsonian Institution Press, pp. i-xvi, 1199-2209. (page 1366, Combination in Pheidole)
- Sumner, S., Nash, D.R., and Boomsma, J.J. (2003). The adaptive significance of inquiline parasite workers. Proc. Biol. Sci. 270, 1315–1322.
- Wheeler, W. M. 1922k. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. IX. A synonymic list of the ants of the Malagasy region. Bull. Am. Mus. Nat. Hist. 4 45: 1005-1055 (see also)
- Wilson, E.O. (1971). The Insect Societies (Harvard University Press).
- Wilson, E.O. (1984). Tropical social parasites in the ant genus Pheidole, with an analysis of the anatomical parasitic syndrome (Hymenoptera: Formicidae). Insectes Soc. 31, 316–334.
References based on Global Ant Biodiversity Informatics
- Fisher B. L. 1997. Biogeography and ecology of the ant fauna of Madagascar (Hymenoptera: Formicidae). Journal of Natural History 31: 269-302.
- Fisher B. L. 2003. Formicidae, ants. Pp. 811-819 in: Goodman, S. M.; Benstead, J. P. (eds.) 2003. The natural history of Madagascar. Chicago: University of Chicago Press, xxi + 1709 pp.
- Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. IX. A synonymic list of the ants of the Malagasy region. Bulletin of the American Museum of Natural History 45: 1005-1055