38 



TahaninoR, more slender in Chrysops, and relatively small and 

 inconspicuous in Pangonia. The body is clothed with short hair 

 and totally devoid of the large bristles termed macrochaetse. The 

 wings, which in the resting position diverge at the tips or are 

 somewhat tectiform {i.e., sloping like the roof of a house), may 

 be hyaline or nearly so, but are often more or less infuscated, and 

 frequently spotted, blotched, or otherwise marked with dark 

 brown or black ; the wing-markings in Hcematopota and in the 

 majority of species of Ghrysops are highly characteristic. The 

 legs, which are of moderate length, are as a rule by no means 

 powerfully developed, and often appear comparatively weak, but 

 the tibiae are sometimes enlarged, and those of the front legs in 

 certain species of Tdbanus are remarkably swollen. 



With the possible exception of certain species of Pangonia {sens, 

 lat.) in which the proboscis is of exceptional length, the blood- 

 sucking habit is universal in the female sex, though there is reason 

 to believe that when blood is not procurable the females will also 

 feed as the males do, on dew on leaves, the nectar of flowers, " upon 

 the juices of plants, the honey-dew secreted by plant-lice and scale 

 insects, and similar substances."* The females of the majority of 

 species are excessively blood-thirsty during the hot hours of the 

 day, and thrust themselves on the notice of travellers owing to 

 their size and pertinacity, especially in attacking domestic animals, — 

 horses, cattle, and camels often streaming with blood in consequence 

 of their attacks ; to human beings the bites are painful, though the 

 effects are not as a rule so lasting as those produced by the bites of 

 Midges and other smaller blood-sucking flies. The species of 

 Hcematopota and the smaller species of Tabanus are remarkable for 

 the quietness with which they alight on their victims, the sharp 

 prick of the bite being often the flrst intimation of the presence of 

 the fly ; the larger species of Tabanus, however, betray their 

 approach by their deep hum. Once the operation of sucking blood 

 is fairly advanced, Tabanidse, like other blood-sucking Diptera, 

 may easily be captured or killed. Owing to their non-aggressive 



* Gj. S. W. Williston, "Manual of North American Diptera." Third Edition, 

 p. 178 (New Haven: James T. Hathaway, 1908). 



