2 The Ohio Naturalist. [Vol. VII, No. 2, 



densely wooded tract on rather low and level ground is often 

 referred to as a swamp. Here these flies abound, and at times 

 are so abundant that it is impossible to drive some horses into 

 their domains. Other animals when compelled to withstand 

 their attacks are difficult to control, for the bites are numerous 

 and severe. It is hardly possible to describe their abundance 

 properly, they must be seen to be appreciated fully. 



Although the different species are much alike in general 

 appearance, they are quite easily separated when both sexes of 

 all of them are at hand. Some have the eyes hairy, a character 

 which is most conspicuous in the male; in the eyes of some of 

 the males the factes are all nearly of the same size, in others 

 there is a very small area of large factes on the disc of each eve, 

 while in others the area of large facets is so extended that two- 

 thirds of the extent of the eyes is included. Some of the species 

 have the eyes pilose and here the difference in the extent of the 

 area of large factes is as pronounced as in the other case. Where 

 there are no large facets the head is smaller than in the cases 

 where these are of large extent. Some species have a short 

 stump of a vein near the base of the branch of the third longi- 

 tudinal, and good specific characters exist in the coloration of the 

 posterior femora. The last two characters seem rather trivial 

 when used in reference to the members of the family in general, 

 but I have found that in this group, when used in connection 

 with the structure of the eyes of the male, they are very constant 

 and consequently may be used with good results in separating 

 the females. The banding of the eyes and the coloration of the 

 thorax and abdomen are specific characters in some cases; also 

 the relative size of the first antennal segment of the various 

 species is of value, but as this last can be expressed only as a 

 comparison with some other species its value in keys and 

 descriptions is very limited. 



In some of the species the males have the habit of hovering 

 in the sunshine as the Syrphid flies do. This habit was only 

 observed by myself in two species, both belonging to the section 

 with uniform sized facets. The first observation was made in 

 reference to the species I have identified as Tabanus truquii, 

 near Sanarate, Guatemala. While riding on horseback along 

 the main road I saw the fly hovering al^out six or eight feet above 

 the ground in bright sunshine. The specimen was accommo- 

 dating enough to remain in the same place until I dismounted, 

 got mv net together and captured it. The other species I 

 observed along the railroad near Puerto Barrios. I had been 

 walking where the track was more or less shaded, but rather 

 suddenly coming out into an open place where the sun's says 

 were not obstructed, I could see dozens of Tabanids hovering 

 just above mv head and succeeded in capturing a number of 



