CassillDeby Lee Cassill
Associate Chair, Associate Professor, Ph.D., Florida State University, 1996
Email: Dr. Deby Cassill
Phone: (727) 873-4064 (O), or (727) 873-4832 (Lab)

“Why do some offspring give up their reproductive rights?” The existence of sterile adults in ants, honey bees, social wasps, termites, naked mole rats and humans (post-menopausal females) has been a long-standing enigma for biologists—one that mystified the likes of Charles Darwin (1859) who Darwin wrote:

“I will…confine myself to one special difficulty, which at first appeared … fatal to my whole theory [of natural selection].  I allude to the neuters … for these neuters often differ widely in instinct and in structure from both the males and fertile females, and yet, from being sterile, they cannot propagate their kind… This difficulty…I believe, disappears, when it is remembered that [natural] selection may be applied to the family, as well as to the individual.”

– Research opportunities with Dr. Cassill

Darwin’s “applied to the family” hypothesis spawned a number of models that attempted to explain the evolution of altruistic offspring including kin selection, reproductive skew and bet-hedging models. The unspoken assumption central to these models was that offspring were initially created equal; differences in the fertility of adults emerge from transactions such as altruistic “giving,” or coercive “taking” Dr. Cassill has developed a maternal investment model that departs from an assumption of offspring equality and instead proceeds with an assumption of offspring inequality. In short, right from the beginning, “Moms don’t pack their kids’ lunch boxes equally,” (M. Ghiselin, personal communication). An assumption of inequality alters the solution to the enigma of Darwin’s altruistic “neuters” from a moral question, “Why do some offspring give up their reproductive rights?” to a risk- management question, “In risky environments, how many disposable spares must a matriarch invest in to ensure the survival of two sexually mature heirs, one to replace her and one to replace her mate?”  Currently, Dr. Cassill’s research is focused on gathering field data to test the assumptions and predictions of her maternal risk-management model on the evolution of diversity “within” species from bacteria to mammals.

BBC Media: Sleeping Ants

Selected Publications

(Click here for extended publications)

*Cassill, D.L. 2014. What can ants tell us about corporate social responsibility? Handbook of Research on Marketing and Corporate Social Responsibility Eds: Ronald Paul Hill and Ryan Langan. Edward Elgar Publishing Ltd, Abingdon, Oxon UK.

Dellert, L., D. O’Neal, D.L. Cassill. 2014. Effects of Nest Relocation and Beach Renourishment on the Success of Loggerhead Sea Turtle Hatchlings (Caretta caretta) Journal of Herpetology 48: 186-187.

Asano, E. and D.L. Cassill. 2012. Modeling seasonal fluctuations in colony size in the fire ant, Solenopsis invicta. Journal of Theoretical Biology 305:70-77.

Asano, E. and D.L. Cassill. 2011. Impact of worker longevity and other endogenous factors on colony size in the fire ant, Solenopsis invicta. Insectes Sociaux 58: 551-557.

Cassill, D.L. 2011. Sex ratio theory is a contradiction, not an extension, of kin selection. The Open Evolution Journal 5:5-7.

Cassill D.L. Hardisty B.E. and Watkins A. 2011. Skew selection solves the enigma of altruism’ in the Shedao pit-viper, Gloydius shedaoensis. Journal of Bioeconomics 13:17–29.

Hardisty, B.E. and D.L. Cassill 2010. Memes and the Ecological Niche. Biological Theory 5:1-3.

Hardisty, B.E. and D.L. Cassill. 2010. Extending eusociality to include vertebrate family units. Biology and Philosophy 25:437-440.

Allen, S. and D.L. Cassill 2010. Skew selection theory applied: The wealth and welfare of nations. Journal of Sociology and Social Welfare 37:115-134.

Cassill, D.L. and A. Watkins. 2010. The emergence of cooperative hierarchies through natural selection processes. Journal of Bioeconomics (12) 29-42.

Cassill, D.L. and D. Singh. 2009. Ambidextrous mandibles in the fire ant, Solenopsis invicta. Annals of the Entomological Society of America 102(4):713-716.

Cassill, D.L., Skye Brown, Devon Swick 2009. Polyphasic wake/sleep episodes in the fire ant, Solenopsis invicta. Journal of Insect Behavior 22:313-323.

Cassill, D.L., Kim Vo and B. Becker. 2008. Young fire ants feign death and survive aggressive neighbors. Naturwissenschaften  95:617-624.

Cassill, D.L. and S.B. Vinson. 2007. Effects of larval secretions on queen fecundity in the fire ant. Annals of the Entomological Society of America 100:327-332.

Cassill, D.L., I. Kuriachan and S.B. Vinson. 2007. A test of two skew models to explain cooperative breeding among unrelated individuals. Journal of Bioeconomics 9:19-37.

Cassill, D.L. and R.P. Hill 2007. A naturological approach to corporate governance: An extension of the Frederick model of corporation-community relations. Business and Society 46:286-303.

Cassill, D.L., Anthony Greco, Rajesh Silwaland Xuefeng Wang. 2007. Opposable spines facilitate fine and gross object manipulation in fire ants. Naturwissenschaften 94:326-332. Online in 2006 ( ). Featured in Nature, Research Highlights, Handy Legs, 446:834 (2007).

Cassill, D.L. 2006. Why skew selection, a model of parental exploitation, should replace kin selection. Journal of Bioeconomics 8: 101-119.

Cassill, Deby L., James Butler, S. Bradleigh Vinson and Diana Wheeler 2005. Cooperation in prey digestion between workers and larvae in the ant, Pheidole spadonia. Insectes Sociaux 52:339-343.

Cassill, D.L. 2005. The social gene. Journal of Bioeconomics 7:73 – 84.

*Cassill, D.L. and A. Watkins. 2004. Mogul games: In defense of inequality as an evolutionary strategy to cope with multiple agents of selection. In: Advances in Austrian Economics (Ed. R. Koppl). Kluwer Academic Publisher, Norwell, MA. 7:35-59.

Hill, R.P. and D.L. Cassill. 2004. The naturological view of the corporation and its social responsibility: An extension of the Frederick model of corporate-community relations. Business and Society Review 109:281-296.

Cassill, D.L.  2003. Skew selection: Nature favors a trickle-down distribution of resources in ants.  Journal of Bioeconomics. 5:83-96.

Cassill, D.L. 2003. Rules of supply and demand regulate recruitment to food in the fire ant, Solenopsis invicta. Behavioral Ecology and Sociobiology. 54:441-450.

Cassill, D.L. 2002. Yoyo-bang: A risk aversion investment strategy by a perennial insect society. Oecologia 132:150-158.

Cassill, D.L. 2002.  Brood care strategies by newly-mated monogyne Solenopsis invicta queens during claustral colony founding (Hymenoptera: Formicidae)Annals of the Entomological Society of America 95:208-212.

Cassill, D.L., W.R. Tschinkel and S. B. Vinson. 2002. Nest complexity, group size and brood rearing in the fire ant, Solenopsis invicta. Insectes Soc. 49:158-163.

Cassill, D.L. and W.R. Tschinkel. 2000. Behavioral and developmental homeostasis the fire ant, Solenopsis invicta. Journal of Insect Physiology 46:933-939.

Cassill, D.L. and W.R. Tschinkel. 1999. Task selection by workers of the fire ant, Solenopsis invicta. Behavioral Ecology and Sociobiology 45:301-310.

Cassill, D.L. and W.R. Tschinkel.  1999. Regulation of diet in the fire ant, Solenopsis invicta. Journal of Insect Behavior 12:307-327.

Cassill, D.L. and W.R. Tschinkel. 1999. Effects of colony-level attributes on larval feeding in the fire ant, Solenopsis invicta. Insectes Sociaux 46:261-266.

*Cassill, D.L. and W.R. Tschinkel. 1999. Information flow during social feeding in ant societies. In: Information Processing in Social Insects (Eds: C.T. Detrain and J.L. Pasteels). Birkauser Verlag, Basel, Switzerland. 69-81.

Cassill, D.L., A. Stuy and R. Buck. 1998. Emergent properties of food distribution among fire ant larvae. Journal of Theoretical Biology 195:371-381.

Cassill, D.L. and W.R. Tschinkel. 1996. A duration constant for worker-larva trophallaxis in fire ants.  Insectes Sociaux 43:149-166.

Cassill, D.L. and W.R. Tschinkel. 1995. Allocation of liquid food to larvae via trophallaxis in colonies of the fire ant, Solenopsis invicta. Animal Behaviour, 50:801-813.

Miller, T., D.L. Cassill, C. Johnson, C. Kindell, J. Leips, D. McInnes, T. Bevis, D. Mehlman and R. Richard. 1994. Intraspecific and interspecific competition of Wyenmyia smithii (Diptera: Culicidae) in pitcher plant communities. Amer. Medl. Nat. 131:136-145.


BSC 4910 (Undergraduate Research)
BSC 3402L Experimental Biology Lab (Research Methods)
ZOO 4512 (Sociobiology)
ZOO 4513C (Animal Behavior)

Interested in Animal Behavior?

Contact Dr. Deby Cassill