ZOOLOGICAL DEPARTMENT. 401 



milk. It is said that the flies confine their attacks solely to horned cattle. 

 If this is so, it is ciuite a point in favor of dehorning. 



THE FLY. 



The Horn Fly is an introduced species probably brought over from 

 Europe along with some importations of cattle, but just when or how is 

 unknown. In size the fly is only about half as large as the common house 

 fly {Musca domesfica) which it resembles closely in a general way, but 

 differs in many minute points. It is of a nearly uniform dark ash gray, 

 almost black, while the house fly has distinct gray bars on the thorax 

 and flesh colored patches at the base of the abdomen on either side. There 

 is still more of a difference between it and the common cattle fly (Siomoxys 

 calcitrans) found feeding on the legs and other parts of the cattle later in 

 the season. This latter is about the size of the house fly and has a light 

 dusty gray appearance with darker bars on the thorax and seven dark 

 spots on the abdomen. The horn fly will most usually be recognized at 

 once by its peculiar habit of appearing in swarms and in feeding with the 

 wings spread, but should this and the brief comparison with the other two 

 common species be insufficient, the following original description by Dr. 

 Williston may aid and so is given. 



•' Male. — 3.5 to 4 m. m. Sides of the front gently concave, in its narrowest width 

 about equal to one-fourth the length of the front from the foremost ocellus to the base 

 of the antennae; in the middle a narrow dark brown stripe; a single row of slender 

 bristles on each side. Antennas brownish red; second joint slightly tumid; third joint 

 a little longer than broad, with its inferior angle rectangular; arista swollen at base 

 (which is black); the pectinations long. The narrow sides of the front, and the still 

 narrower facial and genial orbits, silvery gray, with a slight yellowish cast; facial fovas 

 and cheeks blackish, the latter clothed with yellowish hair. Palpi black, the inner 

 surface and immediate base more yellowish; gently spatulate in shape, nearly as long 

 as the proboscis, and extending two-thirds of their length beyond the oral margin. 

 Mesonotum sub-shining black in ground color, but mostly concealed beneath a brown- 

 ish dust, and with only faint indications of stripes. Dust on the pleura more grayish. 

 Abdomen with similar dust; in the middle with a more brownish, sub-interrupted 

 stripe, and narrow dark posterior margins to the segments. Femora black or very deep 

 brown; first two pairs of tibii« and tarsi brownish yellow or luteous, the hind tibia? and 

 tarsi blackish brown; hind tibiae on the posterior surface with noticeable, erect, sub- 

 apical bristles; hind tarsi about as long as their tibia?, the first three joints widened 

 from base to tip of each, so as to form a distinct serration on their inner acute angles, 

 each of which terminates in a long hair. Wings with a light blackish tinge (due to 

 microscopic pubescence), the immediate base yellowish; first posterior cell rather 

 symmetrically narrowed, to terminate broadly at the extreme tip of the wing. 



''Female. — Front straight on the sides, its width about equal to one-half the distance 

 from the foremost ocellus to the base of the antenna?; the median deep brown stripes 

 about as the lateral pruinose portion. Palpi yellow, with the margins and tips black- 

 ish. Legs more yellowish; hind tarsi regular; pulvilli and claws small." 



LIFE HISTORY. 



As far as known, the fly breeds entirely in manure fresh from the stock. 

 The depositing of eggs is described in Insect Life (loc. cit.) as follows: 

 "As the operation commenced forty or fifty of the flies moved from the 

 flank to the back of the thigh near the " milk mirror," and at the close of 

 the operation they were seen to dart instantly to the dung and to move 

 quickly over its surface, stopping but an instant to deposit an egg. The 

 abdomen and ovipositor were fully extended and the wings were held in a 

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