Field Guide to Venomous and Medically Important Invertebrates ...

are the natural vectors of Leishmania, mechanical transmission of these parasites by stable flies
is considered possible via contaminated mouthparts. The mouthparts or feet of these flies can
transfer parasites from a lesion to a non-leishmanial lesion under experimental conditions.
However, such an occurrence is considered a rarity. Under laboratory conditions, stable flies
have also been implicated as potential mechanical vectors of several species of trypanosomes.
Horse flies and deer flies (Family Tabanidae)
Horse and deer flies are distributed worldwide in tropical and temperate environments. The
primary nuisance genera include Tabanus (horse flies) and Chrysops (deer flies). The
predaceous larvae of tabanids are aquatic or semi-aquatic and occur in a variety of habitat types,
and other species are terrestrial. Deer flies are generally smaller than horse flies, and some
species in the latter group can exceed one inch in size. The eyes of many tabanids are often
brightly colored with iridescent markings. Tabanids also are strong and fast fliers and they will
actively pursue a potential host. Female tabanids feed on blood to nourish their eggs, and, in
doing so, they can inflict painful bites with their biting-slashing mouthparts. Male tabanids feed
on pollen and nectar. Feeding occurs exclusively during daylight. Although tabanids are
generally considered to be an annoyance and not vectors of human disease, some species have
been implicated as vectors of tularemia and anthrax in North America, and parasitic filarial
worms (e.g., Loa loa) in Africa.
Figure 201. Deer fly (Chrysops sp.), North America. Photo: source unknown.
Figure 202. Deer fly (Chrysops), North America. Photo: source unknown.
Figure 203. Deer fly (Chrysops sp.), Thailand. Photo: John Moore.
Figure 204. Unknown species of horse fly, Thailand. Photo: John Moore.
Figure 205. View of Chrysops head showing mouthparts. Photo: John Moore