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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 91, Num. 2, 1996, pp. 159
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Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(1),
Mar/Apr 1996
RESEARCH NOTE: Seasonality of Phaeotabanus fervens
(Diptera: Tabanidae) in the Pantanal Region, Brazil
Antonio Thadeu M Barros
Centro de Pesquisa Agropecuaria do Pantanal/EMBRAPA, Rua 21 de
Setembro 1880, 79320-900 Corumba, MS, Brasil
Code Number: OC96030
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Phaeotabanus fervens (Linnaeus), 1758 is a
neotropical tabanid species distributed from Venezuela to
Argentina (GB Fairchild 1971 Ed Mus Zool Univ S o Paulo
28: 28-56). This horsefly is one of the few species reported
biting exclusively on caimans (Caiman sclerops,
Melanosuchus niger, Paleosuchus palpebrosus
and Paleosuchus trigonatus) only on their head (F Medem
1981 Cespedesia 10: 123-191). Probably due
to its host specificity very few data about this species are
available. Caiman feeders such as Lepiselaga crassipes
(F.), Phaeotabanus cajennensis (F.) and Phaeotabanus
fervens (Medem loc. cit.) occur in the Pantanal region
and unidentified general photographic records are available (H
Palo Jr 1992 Pantanal Ed Cor/Ac o 123 pp.).
The Center of Agricultural Research for Pantanal
(CPAP/EMBRAPA), located in the Corumba town near the Bolivian
frontier at the western border of the Brazilian Pantanal,
mantained some caimans (Caiman crocodilus yacare) for
biological studies. On some occasions P. fervens could be
frequently observed flying against window glasses around the
caiman pools. These tabanids were basically seen only at these
sites and despite the lack of feeding observations it seemed
obvious that their presence was due to the caimans (the only host
present except humans).
A few sporadic tries to capture tabanids using caimans as bait
were carried out on a ranch 150 km from town but no individuals
were caught. Also monthly surveys, carried out from 1992 to 1994
with canopy traps and horses, were unsuccessful for catching
P. fervens in the same area. It is possible that the
collections were conducted outside of the spatial or temporal
distribution of the flies and/or the techniques used were not the
most effective methods for this species.
In more than 300 observations, from 1988 to 1993, 77 P.
fervens voucher specimens were caught manually or with sweep
nets from the windows near the caiman pools at CPAP. It was
verified that this species showed a very defined seasonal
pattern, occurring from September to November, after the
beginning of the rainy season. In Colombia, Medem (loc.
cit.) found P. fervens from November to March during
collections over five years, however, he gathered some specimens
in September and October during an expedition to the Brazilian
Amazon. In the Pantanal the population peak of P. fervens
was generally observed in October (also in November) and none was
seen in December. This distribution coincides with the peak of
most tabanid species in the region.
Since other haematophagous flies are recorded as trypanosome
vectors for crocodiles (CA Hoare 1929 Trans R Soc Trop Med
Hyg 23: 39-56) and there is a high prevalence (46%)
of Trypanosoma spp. infection in C. c. yacare from
Pantanal (VLB Nunes, ET Oshiro, personal communication), it would
be important to investigate a possible role played by tabanid
species in trypanosome transmission to caimans.
Received 20 June 1995
Accepted 15 December 1995
Copyright 1996 Fundacao Oswaldo Cruz
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