Department of Entomology & Nematology
University of Florida, Gainesville, FL 32611-0620
May 8, 1995
The tsetse fly Glossina palpalis (Diptera: Glossinidae) probably has no match among haematophagous insects in its vertebrate host range. According to Jordan et al. (1962) this fly can feed on any vertebrate it contacts. It is also not responsive to host derived odors presently being evaluated as olfactory baits and incorporated in trapping technology strategies for tsetse flies (Williemse and Taken 1994).
Haematophagy or the utilization of blood as food occurs in six insect orders. The order Diptera (true flies) has the largest number of haematophagous species and includes endoparasitic and ectoparasitic forms (Lehane 1991). The ectoparasites include those that stay permanently on their hosts and those that are off their hosts except when feeding. Those ectoparasites that stay off their hosts, range from most to least host specific with regard to both their host locating (trailing) and host preference patterns. According to Askew (1971) tsetse flies are not at all restricted in their choice of hosts but different species have different habitat preferences and are classified into three major ecological groupings on the basis of habitat preferences: open savanna or grassland [morsitans species group] dense humid forests associated with water bodies [palpalis]; and other forests [fusca].
Vertebrate host specificity of haematophagous insects was obtained from medical and veterinary entomology textbooks and journals. Help in finding a champion was obtained from the Entomo-L Listserv.
Stomoxys calcitrans was a candidate on the basis of being a cosmopolitan livestock pest and attacking up to 30 different species among mammals, birds, reptiles, and even amphibians (Bishop 1913, Surcouf 1923, Hoskins 1933, Haefez & Gammal-Eddin 1959, Greenberg 1971). According to Jordan et al. (1961 and 1962), Glossina palpalis has a wider range of acceptable hosts than any other species in West Africa. Species of the palpalis group of tsetse flies feed on any vertebrate they encounter ranging from mammals and reptiles to birds (Weitz 1963, 1971; Harwood & James 1979). Information on feeding habits and preferences by tsetse flies relies on identifying blood meals of wild caught tsetse flies using the precipitin test described by Weitz (1956). Weitz and Glasgow (1956) observed that the host range for G. palpalis fuscipes in East Africa included mammals, with birds and reptiles having equal importance and even suggested that lungfish (Protopterus sp.) could be a source of blood meals. Nash (1948) in West Africa, compared G. palpalis to G. tachinoides and observed that G. palpalis will fly higher and hunt for hosts in dense undergrowth. Williemse and Taken (1994) state that tsetse flies of the palpalis group are not responsive to the conventional vertebrate host derived odor cues that tsetse flies of the morsitans group readily respond to.
The least host specific vertebrate blood sucker should be an insect documented to feed on any available vertebrate host. Greenberg (1971) discussed Glossina spp. as vectors of trypanosomes, having bimodal flight activity, etc., but did not attempt to categorize tsetse fly hosts in the same way as he did for Stomoxys calcitrans and other flies. G. palpalis is probably least specialized in host selectivity as there is no limit documented for vertebrate species that it can feed on (Weitz & Glasgow 1956; Jordan et al. 1961, 1962; Weitz 1963). This tsetse fly generally feeds while inside dense humid forest habitats where trailing hosts by olfaction would be arduous. Under such circumstances, it would be advantageous to compromise by feeding on any vertebrate host encountered by sight rather than by relying on olfactory cues.
I thank Dr. W. Symondson, University of Wales, Cardiff, for information that led me to search tsetse flies for the least specific sucker of vertebrate among insects; and Dr. A. Broce, Kansas State University, for suggesting the stable fly, S. calcitrans, as an alternative candidate.
- Askew, R.R. 1971. Parasitic insects. Heinemann Educational Books, London.
- Bishop, F.C. 1913. The stable fly Stomoxys calcitrans as an important livestock pest. J. Econ. Entomol. 6: 112-126.
- Greenberg, B. 1971. Flies and disease. Volume I and II. Princeton University Press, Princeton, New Jersey.
- Haefez, M. & F.M. Gammal-Eddin. 1959. Feeding habits of Stomoxys calcitrans and S. sitiens in Egypt. Bull. Soc. Entomol. Egypt 43: 291-301.
- Harwood, R.H. & M.T. James. 1979. Entomology in human and animal health. Macmillan, Inc. New York.
- Hoskins, M. 1933. An attempt to transmit yellow fever virus by dog fleas Ctenocephalides canis Curt. and flies Stomoxys calcitrans Linn. J. Parasitol. 19: 299-303.
- Jordan, A.M., F. Lee-Jones & B. Weitz. 1961. The natural hosts of tsetse flies in forest belts of Nigeria and southern Cameroon. Ann. Trop. Med. Parasit. 55: 167 -179.
- Jordan, A.M., F. Lee-Jones & B. Weitz. 1962. The natural hosts of tsetse flies in northern Nigeria. Ann. Trop. Med. Parasit. 56: 430-442.
- Lehane, M.J. 1991. Blood sucking insects. Harper Collins, London.
- Nash, T.A.M. 1948. Tsetse flies in British West Africa. H.M. Stationery Office, London. [Not seen; cited in in Askew 1971, p. 58].
- Surcouf, J.M.R. 1923. Deuxiene note sur les conditions biologiques du Stomoxys calcitrans Linnaeus. Bull. Mus. Hist. Nat. Paris 29: 168-172.
- Weitz, B. 1956. Identification of blood meals of blood sucking arthropods. Bull. World Hlth. Org. 15: 473.
- Weitz, B. 1963. The feeding habits of Glossina. Bull. World Hlth. Org. 28: 711 -729.
- Weitz, B. 1971. The hosts of Glossina, pp. 317-326. In H. W. Mulligan [ed.], African trypanosomiasis. George Allen & Unwin, London.
- Weitz, B. & J.P. Glasgow 1956. The natural hosts of some species of Glossina in East Africa. Trans. R. Soc. Trop. Med. Hyg. 40: 593.
- Williemse, L.P.M. & W. Taken. 1994. Odor induced host location in tsetse flies (Diptera: Glossinidae). J. Med. Entomol. 31: 775-794.