, Volume 91, Issue 11, pp 539–543

Parasitoids and competitors influence colony-level responses in the red imported fire ant, Solenopsis invicta

  • Natasha J. Mehdiabadi
  • Elizabeth A. Kawazoe
  • Lawrence E. Gilbert
Short Communication


Social insect colonies respond to challenges set by a variable environment by reallocating work among colony members. In many social insects, such colony-level task allocation strategies are achieved through individual decisions that produce a self-organized adapting group. We investigated colony responses to parasitoids and native ant competitors in the red imported fire ant (Solenopsis invicta). Parasitoid flies affected fire ants by decreasing the proportion of workers engaged in foraging. Competitors also altered colony-level behaviours by reducing the proportion of foraging ants and by increasing the proportion of roaming majors, whose role is colony defence. Interestingly, the presence of both parasitism and competition almost always had similar effects on task allocation in comparison to each of the biotic factors on its own. Thus, our study uniquely demonstrates that the interactive effect of both parasitism and competition is not necessarily additive, implying that these biotic factors alter colony behaviour in distinct ways. More generally, our work demonstrates the importance of studying the dynamics of species interactions in a broader context.


  1. Camilo GR, Phillips SA (1990) Evolution of ant communities in response to invasion by the fire ant Solenopsis invicta. In: Vander Meer RK, Jaffe K, Cedeno A (eds) Applied myrmecology: a world perspective. Westview, Boulder, Colo., USA, pp 190–198Google Scholar
  2. Disney RHL (1994) Scuttle flies: the Phoridae. Chapman and Hall, LondonGoogle Scholar
  3. Feener DH (1981) Competition between ant species outcome controlled by parasitic flies. Science 214:815–817Google Scholar
  4. Folgarait PJ, Gilbert LE (1999) Phorid parasitoids affect foraging activity of Solenopsis richteri under different availability of food in Argentina. Ecol Entomol 24:163–173CrossRefGoogle Scholar
  5. Gordon DM (1989) Dynamics of task switching in harvester ants. Anim Behav 38:194–204Google Scholar
  6. Gordon DM, Mehdiabadi NJ (1999) Encounter rate and task allocation in harvester ants. Behav Ecol Sociobiol 45:370–377CrossRefGoogle Scholar
  7. Hart AG, Bot ANM, Brown MJF (2002) A colony-level response to disease control in a leaf-cutting ant. Naturwissenschaften 89:275–277CrossRefPubMedGoogle Scholar
  8. Mehdiabadi NJ, Gilbert LE (2002) Colony-level impacts of parasitoid flies on fire ants. Proc R Soc Lond Ser B 269:1695–1699CrossRefGoogle Scholar
  9. Mehdiabadi NJ, Kawazoe EA, Gilbert LE (2004) Phorid fly parasitoids of invasive fire ants indirectly improve the competitive ability of a native ant. Ecol Entomol 29:621–627CrossRefGoogle Scholar
  10. Morrison LW (1999) Indirect effects of phorid fly parasitoids on the mechanisms of interspecific competition among ants. Oecologia 121:113–122CrossRefGoogle Scholar
  11. Morrison LW, Dall’Aglio-Holvorcem CG, Gilbert LE (1997) Oviposition behavior and development of Pseudacteon flies (Diptera: Phoridae), parasitoids of Solenopsis fire ants (Hymenoptera: Formicidae). Environ Entomol 26:716–724Google Scholar
  12. Orr MR, Seike SH, Benson WW, Gilbert LE (1995) Flies suppress fire ants. Nature 373:292–293CrossRefGoogle Scholar
  13. Porter SD, Tschinkel WR (1985) Fire ant polymorphism: the ergonomics of brood production. Behav Ecol Sociobiol 16:323–336CrossRefGoogle Scholar
  14. Porter SD, Vander Meer RK, Pesquero MA, Campiolo S, Fowler HG (1995) Solenopsis (Hymenoptera: Formicidae) fire ant reactions to attacks of Pseudacteon flies (Diptera: Phoridae) in southeastern Brazil. Ann Entomol Soc Am 88:570–575Google Scholar
  15. Robinson GE (1992) Regulation of division of labor in insect societies. Annu Rev Entomol 37:637–665CrossRefPubMedGoogle Scholar
  16. Rosengaus RB, Maxmen AB, Coates LE, Traniello JFA (1998) Disease resistance: a benefit of sociality in the dampwood termite Zootermopsis angusticollis (Isoptera: Termopsidae). Behav Ecol Sociobiol 44:125–134CrossRefGoogle Scholar
  17. SAS Institute (2000) SAS/STAT user’s guide, version 8, vols 1, 2, 3. SAS Institute, Cary, N.C., USAGoogle Scholar
  18. Sanders NJ, Gordon DM (2000) The effects of interspecific interactions on resource use and behavior in a desert ant. Oecologia 125:436–443CrossRefGoogle Scholar
  19. Seeley TD (1982) Adaptive significance of the age polyethism schedule in honeybee colonies. Behav Ecol Sociobiol 11:287–293CrossRefGoogle Scholar
  20. Wilson EO (1978) Division of labor based on physical castes in fire ants (Hymenoptera: Formicidae: Solenopsis). J Kans Entomol Soc 51:615–636Google Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Natasha J. Mehdiabadi
    • 1
    • 2
  • Elizabeth A. Kawazoe
    • 1
  • Lawrence E. Gilbert
    • 1
  1. 1.Section of Integrative Biology and Brackenridge Field Laboratory, School of Biological SciencesUniversity of Texas at AustinAustinUSA
  2. 2.Department of Ecology and Evolutionary BiologyRice UniversityHoustonUSA

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