24 MEDICAL ENTOMOLOGY 



EXERCISE 12 



THE STABLEFLY (STOMOXYS CALCITRANS) AND THE HORNFLY 

 OR TEXAS FLY (HEMATOBIA SERRATA) 



ORDER DIPTERA, FAMILY MUSCID2E 



A Comparative Study. 



With specimens of each species of fly before you, note the 

 distinguishing characteristics, indicating the same by means of 

 separate drawings of the parts and by description in your note- 

 book. 



These two species of flies belong to the blood-sucking branch 

 of the Family Muscidae, to which also belongs the genus Glos- 

 sina (Tsetse flies). 



a. Mouthparts. The palpi of Stomoxys are relatively short, 

 while those of Haematobia are long and flattened. The pro- 

 boscis of the latter is also relatively more plump and is not so 

 well thrown forward, when at rest, as in the Stomoxys, due in 

 the latter to a well developed joint at its base. 



b. Wings. Note the close similarity in wing venation. The 

 wings of the stablefly are thrown wide apart when at rest. f 



c. Size. With at least half a dozen specimens of each species 

 before you note the relative size of the individuals. Measure 

 the length of these specimens in terms of millimeters. 



d. Make a large drawing of the head of the hornfly, side view, 

 to show the following parts, compound eye, antenna, and pro- 

 boscis with palpi. 



e. Draw the egg of the hornfly; note the brownish color. En- 

 large sufficiently to indicate general characteristics. 



f. Note differences in the sexes as indicated by the segments 

 of the abdomen. 



