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Gary Dodson
Ball State University
Dept of Biology

Dept of Biology

Antlered Flies

A group of tephritid flies (genus Phytalmia) found in Papua New Guinea and Australia are characterized by extraordinary projections from the heads of males that superficially resemble the antlers of cervids (ref 3).  Their resource defense mating system involves males guarding the limited locations on rotting logs where females lay their eggs (ref 2).  In addition to describing their ecology and behavior, my research addresses questions in the areas of animal conflict theory and the evolution and maintenance of secondary sexual characteristics.  Among the more significant findings from this work has been the idea that head projections such as these fly antlers function as signals rather than weapons, allowing honest assessment of asymmetries between opponents (ref 9).  This may lower the cost of settling contests over female required resources.

A terrific photo story on these flies by Mark Moffett can be found in the November 1997 issue of National Geographic Magazine.

Any of the following links will start a short movie showing males fighting in an Australian antler fly species (Phytalmia mouldsi)

  antlrfly.avi  (316K)  (876K)

  antlrfly.mpg  (152K)










Crab Spiders

A careful perusal of flower heads during mid to late summer will reveal cryptically colored crab spiders (Thomisidae).  Named for their ability to walk sideways rapidly, crab spiders are sit-and-wait, ambush predators.  A ubiquitous species of the eastern United States, Misumenoides formosipes, has been the focus of our studies. Males exhibit precopulatory mate guarding and fight for a position closest to a soon-to-be adult female (ref 4). We have determined that residency status, relative size, and previous contest experience influence the outcomes of fights, with previous winning experience (even a single result) being the best predictor (refs 5, 7).

Recent research has focused upon the cues used by male spiders to optimize their searches for potential mates within their complex habitat structure.  Chemical cues from the plants upon which females reside have been implicated (ref 9). The specific chemistry involved is currently under investigation in collaboration with chemistry professor Dr. Patti Lang.

A surprising finding was that males will feed upon floral nectar (ref 8).  This was an original revelation for spiders, but has since been reported for other species.  We would like to know how nectarivory might affect male fighting and mating success. 




Hilltopping Bee Flies  

Males of a brand new generation of the bombyliid species Comptosia tutela fly to a hilltop in southeast Queensland, Australia each spring.  Consecutive years of observations revealed that the dominant individuals occupied the exact same territories each year despite that a) they had never been to the hilltop before and b) the characteristics of the territories were variable and not unlike many unoccupied sites (ref 10).  Spectacular aerial duels between competing males carry opponents to heights beyond visual range.  Residency status was a predictor of contest success, while neither size nor age was a factor (ref 6).  We are particularly interested in identifying the cues used by nave males to locate these territories each year.

Insect Galls

I have addressed questions regarding the evolutionary relationships between gall insects and their host plants.  I demonstrated experimentally with tephritid flies on rabbitbrush that the morphology of the gall was ultimately controlled by the insect and not the plant (ref 1), an assumption previously supported only by circumstantial evidence.  Gall systems provide one of the most fascinating ways to explore the dynamics of three trophic level interactions.  Preliminary evidence in the Aciurina/rabbitbrush system suggests that gall morphology plays a significant role in protecting the gall former from attack by parasitoid wasps.



References Cited  [For a more complete publication list, go here]

1)  Dodson, G.  1991.  Control of gall morphology: tephritid gall‑formers (Aciurina spp.) on rabbitbrush (Chrysothamnus).   Ecological Entomology 16: 177‑181.

2)  Dodson, G. N.  1997.  Resource defense mating system of antlered flies, Phytalmia spp.  Annals of the Entomology Society of America.  90: 496-504.

3)  Dodson, G. N.  2000.  Behavior of the Phytalmiinae and the evolution of antlers in tephritid flies.  Pp. 175-184  In: Fruit flies (Tephritidae): Phylogeny and Evolution of Behavior.  Aluja, M. and A. Norrbom (eds.).  CRC Press.

 4)  Dodson, G. and M. Beck.  1993.  Precopulatory guarding of penultimate females by male crab spiders, Misumenoides formosipesAnimal Behaviour 46: 951‑959.

5)  Dodson, G. N. and A. T. Schwaab.  2001.  Body size, leg autotomy, and prior experience as factors in the fighting success of male crab spiders, Misumenoides formosipes.   Journal of Insect Behavior 14: 841-855.

 6)  Dodson, G. and D. K. Yeates.  1990.  The mating system of a bee fly.  2. Factors affecting individual male success.  Journal of Insect Behavior 3: 619‑636.

 7)  Hoefler, C. D. 2002.  Is contest experience a trump card?  The interaction of residency status, experience, and body size on fighting success in Misumenoides formosipes (Araneae; Thomisidae).  Journal of Insect Behavior 15: 779-790.

 8)  Pollard, S. D., M. W. Beck, and G. N. Dodson.  1995.  Why do male crab spiders drink nectar?  Animal Behaviour 49: 1443-1448.

9)  Stellwag, L. and Dodson, G. N.  2010  Navigation by male crab spiders Misumenoides formosipes (Araneae: Thomisidae): floral cues may aid in locating potential mates.  Journal of Insect Behavior  23: 226 335.

10)  Wilkinson, G. and G. N. Dodson.  1997.  Function and evolution of antlers and eye stalks in flies.  Pp. 310-328.  In: The Evolution of Mating Systems in Insects and Arachnids.  Choe, J.C. and B.J. Crespi (eds.).  Cambridge University Press.

11)  Yeates, D. K. and G. Dodson.  1990.  The mating system of a bee fly.  1. Nonresource-based hilltop territoriality and a resource-based alternative.  Journal of Insect Behavior 3: 603‑617.