no 



Parasitic Arthropoda 



nearly wholly covered with brown hairs, gray, with markings as 

 ■shown in the figure. Length one mm. 



J ohannseniella Will, is a 

 wide-spread genus related 

 to the foregoing. Its 

 mouth-parts are well 

 adapted for piercing and 

 it is said to be a persistent 

 blood sucker, particularly 

 in Greenland. This genus 

 is distinguished from Culi- 

 coides by its bare wings, 

 the venation (fig. 163,0), 

 and the longer tarsal claws. 

 There are over twenty 

 North American species. 

 In the Southwestern United States, Tersesthes torrens Towns, 

 •occurs, a little gnat which annoys horses, and perhaps man also, by 

 its bite. It is related to Culicoides but differs in the number of 

 antennal segments and in its wing venation (fig. 163,0). The fly 

 measures but two mm. in length and is blackish in color. The 

 antennas of the female have thirteen segments, the palpi but three, of 

 Tvhich the second is enlarged and swollen. 



79. Chrysops univittatus. (X4). After Osborn 



Tabanidae or Horse-Flies 



The Tabanidae, — horse-flies, ear-flies, and deer-flies, — are well- 

 known pests of cattle and horses and are often extremely annoying 

 to man. The characteristics of the family and of the principal North 

 American genera are given in the keys of Chapter XII. There are 

 -over 2500 recorded species. As in the mosqtiitoes, the females 

 alone are blood suckers. The males are flower feeders or live on 

 plant juices. This is apparently true also of the females of some of 

 the genera. 



The eggs are deposited in masses on water plants or grasses and 

 sedges growing in marshy or wet ground. Those of a common 

 species of Tabanus are illustrated in figxire 80, a. They are placed 

 in masses of several hundred, light colored when first deposited but 

 turning black. In a week or so the cylindrical larvae, tapering at 

 l)Oth ends (fig. 80, b), escape to the water, or damp earth, and lead 



