I IO 
Parasitic Arthropoda 
nearly wholly covered with brown hairs, gray, with markings as 
shown in the figure. Length one mm. 
Johannseniella 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. i63,e). The fly 
measures but two mm. in length and is blackish in color. The 
antennae of the female have thirteen segments, the palpi but three, of 
which the second is enlarged and swollen. 
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 mosquitoes, 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 figure 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 
both ends (fig. 80, b ), escape to the water, or damp earth, and lead 
