26 MEDICAL ENTOMOLOGY 



EXERCISE 14 



THE Box AND WARBLE FLIES 



ORDER DIPTERA, FAMILY CESTRnXdE 



A. With two specimens of (Estridae before you, one Gastro- 

 philus equi, the horse hot, and one Hypoderma lineata, the 

 ox warble fly, study the following characters, noting that the 

 examples are rather thickset and covered with hair, and that 

 the mouthparts are vestigial, the eyes small and bare, the 

 squamae large. 



a. Antenna are small, three-jointed and decumbent, as in the 

 Muscidae. In the horse bot the arista is bare, while in the 

 warble fly it is plumose. 



b. Tarsi of front legs, broad, flattened and hairy in Hypo- 

 derma, while they are slender and less hairy in Gastrophilus. 



c. Wing venation; note the difference between the genera. 



d. Sexual characters; notice the difference between the sexes 

 in the terminal abdominal segments. 



Draw the characteristic details. 



B. Larval Characters. 



a. Segmentation; count the segments, paying especial attention 

 to the terminal ones. 



b. Booklets; in the horse bot note the presence of a pah- of 

 outer booklets used for attachment to the walls of the stomach. 

 Note also a pair of inner straight points (not hooked). Are these 

 anterior or posterior? 



c. Tubercles; in the warble notice the dorsal spindle-shaped 

 tubercles on the median segments and then* arrangement. 



d. Examine a specimen of the head maggot of sheep ((Estrus 

 ovis). 



Draw a specimen of each. 



