One group of flies has evolved to become ectoparasites of bats, showing a plethora of adaptations and life-history strategies to this mode of life. Bat flies live exclusively in the fur and on the wing membranes of this mammalian order, where they feed on host blood. Unlike other ectoparasitic groups, they show an enormous range of variation in eye reduction, in locomotion, and in hold-fast adaptations like ctenidia (combs) and claws. This, coupled with the ecological and taxonomic diversity of bats makes this system especially promising for studies in evolution and ecology.
Morphological diversity of three bat fly species typically found on the Neotropical short-tailed fruit bat, Carollia perspicillata:
(A) Speiseria ambigua, (B) Strebla guajiro, and (C) Trichobius joblingi (from Patterson et al, 2009, Ecography).
Host specificity is influenced by the behavior and ecology of both parasite and host. The biological and ecological characteristics of bats and flies should facilitate transfers between host species, leading over time to non-specific host-parasite associations. Yet bat-bat fly associations are typically highly host-specific. During his post-doc at Field Museum, Carl Dick and I curated the world's largest collection of bat flies. This now guides our understanding of host associations and fuels the taxon-sampling in our phylogenetic work. Undergrad and grad students are involved in this work in Chicago, Buffalo, and Bowling Green.
We have investigated various features of the evolutionary ecology of the bat-bat fly system. We showed that populations of flies on bats include a preponderance of male flies, and that female bats typically carry heavier fly loads. We also showed that both body size and type of roost that a bat occupies can influence the intensity, prevalence and number of its bat fly associates. Conversely, host abundance and geographic range appear to have negligible effects on bat fly parasitism. Now a faculty member at Western Kentucky University, Carl pursues studies on fly phylogeny, taxonomy, development, and ecology, while my work emphasizes bat phylogeny, ecology, and biogeography. We are jointly pursuing tests of the hypothesis that immune-system interactions are responsible for host specificity among bat flies.
Carl Dick and Katha Dittmar removing flies from a fishing bat (Noctilio leporinus) on Vieques Island, Puerto Rico (photo © 2008 by B.D. Patterson).
We are also developing a comprehensive phylogeny for bat flies of the world. This collaborative work is being led by SUNY Buffalo researcher Katha Dittmar. Katha is spearheading the generation of phylogenies using molecular characters, while Carl and his grad students are exploring phylogenetic analyses of morphology. Preliminary results suggest that current conceptions of Streblidae are unnatural--Nycteribiidae renders Streblidae paraphyletic and New World and Old World streblid flies form sister groups. In addition, the Trichobius of conventional usage is massively paraphyletic.
An uncommonly large nycteribiid bat fly (Penicillidia fulvida) on a horseshoe bat (Rhinolophus sp.) along Kenya's South Coast (photo © 2012 by B.D. Patterson).
Our work on bat flies has been supported by two grants from the National Science Foundation. The first allowed us to database bat fly collections to enable powerful, fauna-wide tests of ecological hypotheses, while the other is focused on reconstructing and analyzing bat fly phylogenies. A completed phylogeny should soon allow us to explore the evolution of key innovations in this parasitic relationship, parallel radiations of hosts and parasitic partners, and molecular evolution of proteins involved in vision.
Videos of Carl Dick picking bat flies from a bat in Hell's Gate, Kenya, 2011 (click on image)
Carl Dick picking ectoparasites from a giant mastiff bat, 2011
A nycteribiid bat fly, one of the largest known, in the fur of a Hipposideros bat, 2011
The Field Museum also has stellar collections of many other ectoparasitic arthropods, including mites, ticks, fleas, lice, and bot flies and amblyopinine beetles (which aren't ectoparasites but are mammal associates). We welcome collaborations with colleagues who wish to explore or develop these resources.
Some recent publications on bat flies
These articles are posted as pdfs for the convenience of people making personal copies for their own use. If you wish copies of articles for commercial purposes or for distribution to a class, please write directly to the publishers.
Dick, C. W. & B. D. Patterson. 2006. Bat flies - obligate ectoparasites of bats. Pp. 179-194 In Micromammals and macroparasites: from evolutionary ecology to management (S. Morand, B. Krasnov, and R. Poulin, eds.). Springer-Verlag, Tokyo. pdf (121 kb).
Patterson, B.D., C.W. Dick & K. Dittmar. 2007. Roosting habits of bats affect their parasitism by bat flies (Diptera: Streblidae). Journal of Tropical Ecology 23:177-189. pdf (247 kb).
Dick, C.W. & B.D. Patterson. 2007. Against all odds: explaining host specificity in dispersal-prone ectoparasites. International Journal of Parasitology 37:871-876. pdf (340 kb).
Patterson, B.D., C.W. Dick & K. Dittmar. 2008a. Sex biases in parasitism of Neotropical bats by bat flies (Diptera: Streblidae). Journal of Tropical Ecology 124:387-396. pdf (110 kb).
Patterson, B.D., C.W. Dick & K. Dittmar. 2008b. Parasitism by bat flies (Diptera: Streblidae) on Neotropical bats: effects of host body size, distribution and abundance. Parasitology Research 103:1091-1100. pdf (355 kb).
Patterson, B.D., C.W. Dick & K. Dittmar. 2009. Nested distributions of bat flies (Diptera: Streblidae) on Neotropical bats: artifact and specificity in host-parasite studies. Ecography 32:481-487. pdf (159 kb)
Dittmar, K., C.W. Dick, B.D. Patterson, M.F. Whiting & M. Gruwell. 2009. Pupal deposition and ecology of bat flies (Diptera: Streblidae): Trichobius sp. (caecus group) in a Mexican cave habitat. Journal of Parasitology 95:308-314. pdf (1021 kb)
Pilosof, S., C.W. Dick, C. Korine, B.D. Patterson &
B.R. Krasnov. 2012. Effects of anthropogenic disturbance and climate on
patterns of bat fly parasitism. PLoS One 7(7): e41487. html
Morse, S.F., C.W. Dick, B.D. Patterson & K. Dittmar. 2012. Some like it hot -- Evolution and ecology of novel endosymbionts in bat flies of cave-roosting bats (Hippoboscoidea, Nycterophiliinae). Applied and Environmental Microbiology 78: 8639-8649. pdf (2.7 Mb)
Morse, S.F., S.E, Bush, B.D. Patterson, C.W. Dick, M.E. Gruwell & K. Dittmar. 2013. Evolution, multiple acquisition, and localization of endosymbionts in bat flies (Hippoboscoidea, Streblidae and Nycteribiidae). Applied and Environmental Microbiology 79:2952-2961 pdf (2.8 Mb) SOM (66 kb)