Behavioral Ecology and Sociobiology

, Volume 14, Issue 1, pp 47–54 | Cite as

Caste and division of labor in leaf-cutter ants (Hymenoptera: Formicidae: Atta)

III. Ergonomic resiliency in foraging by A. cephalotes
  • Edward O. Wilson


More than 90% of media workers with head widths 1.8–2.2 mm, comprising the largest and energetically most efficient segment of the foraging force, were removed from four Atta cephalotes colonies containing approximately 8,000 workers. Contrary to expectation, the colonies did not respond by adding workers from adjacent size classes (head width ≦1.6 mm, ≧2.4 mm) to the foraging force (Table 1, Fig. 1). Yet the rate of leaf harvesting remained unaffected, due to the fact that excess workers in the adjacent size classes were already present on a stand-by basis in the foraging area (Table 2, Fig. 2). Moreover, the few survivors in the 1.8–2.2 mm group increased their individual activity by approximately 5x. In control and undisturbed colonies, the prime foragers in the 1.8–2.2 mm group tended to displace the others from the edges of the leaves, where most cutting takes place. When these individuals were removed, the auxiliaries participated more actively.

Brood development was followed through 2 full development cycles after the excision. No differential increase of the extirpated worker class (1.8–2.2 mm) could be detected in the experimental colonies when compared with sham-treated control colonies. As a consequence, this group remained underrepresented in the foraging arenas by about 50% at the end of the first cycle (8 weeks), but was fully replenished by the end of the second cycle (16 weeks).

The size-frequency distributions of the worker pupae belonged to one or the other of three patterns among both experimental and control colonies: unimodal at head width 0.8 mm, unimodal within 1.4–2.0 mm, or bimodal at these two respective positions (Fig. 3). Several colonies shifted from one pattern to another during a single brood cycle (Table 3). A hypothesis of the control of the size-frequency distribution has been developed consistent with these results.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Autuori M (1956) La fondation des sociétés chez les fourmis champignonnistes du genre Atta (Hym. Formicidae). In: Autuori M et al. (eds) L'instinct dans le comportement des animaux et de l'homme. Masson, Paris, pp 77–104Google Scholar
  2. Barrer PM, Cherrett JM (1972) Some factors affecting the site and pattern of leaf-cutting activity in the ant Atta cephalotes L. J Entomol 47:15–27Google Scholar
  3. Eibl-Eibesfeldt I (1967) Atta cephalotes (Formicidae): Schneiden und Eintragen von Blattstücken; Parasiten-Abwehr. Encycl Cinematogr (Inst Wiss Film, Göttingen, no E1407)Google Scholar
  4. Eidmann H (1935) Zur Kenntnis der Blattschneiderameise Atta sexdens L., insbesondere ihrer Ökologie. Z Angew Entomol 22:185–241, 385–436Google Scholar
  5. Gregg RE (1942) The origin of castes in ants with special reference to Pheidole morrisi Forel. Ecology 23:295–308Google Scholar
  6. Nijhout HF, Wheeler DE (1982) Juvenile hormone and the physiological basis of insect polymorphisms. Q Rev Biol 57:109–133Google Scholar
  7. Oster GF, Wilson EO (1978) Caste and ecology in the social insects. Princeton University Press, Princeton, NJGoogle Scholar
  8. Passera L (1974) Différenciation des soldats chez la fourmi Pheidole pallidula Nyl. (Formicidae Myrmicinae). Insectes Soc 21:71–86Google Scholar
  9. Passera L (1977) Production des soldats dans les sociétés sortant d'hibernation chez la fourmi Pheidole pallidula (Nyl.) (Formicidae, Myrmicinae). Insectes Soc 24:131–146Google Scholar
  10. Shepherd JD (1982) Trunk trails and the searching strategy of a leaf-cutter ant, Atta colombica. Behav Ecol Sociobiol 11:77–84Google Scholar
  11. Sokal RR, Rohlf FJ (1969) Biometry. Freeman, San FranciscoGoogle Scholar
  12. Wheeler DE, Nijhout HF (1981) Soldier determination in ants: New role for juvenile hormone. Science 213:361–363Google Scholar
  13. Wilson EO (1980a) Caste and division of labor in leaf-cutter ants (Hymenoptera: Formicidae: Atta). I. The overall pattern in A. sexdens. Behav Ecol Sociobiol 7:143–156Google Scholar
  14. Wilson EO (1980b) Caste and division of labor in leaf-cutter ants (Hymenoptera: Formicidae: Atta). II. The ergonomic optimization of leaf cutting. Behav Ecol Sociobiol 7:157–165Google Scholar
  15. Wilson EO (1983) Caste and division of labor in leaf-cutter ants (Hymenoptera: Formicidae: Atta). IV. Colony ontogeny in A. cephalotes. Behav Ecol Sociobiol 14:55–60Google Scholar

Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • Edward O. Wilson
    • 1
  1. 1.Museum of Comparative ZoologyHarvard UniversityCambridgeUSA

Personalised recommendations