34 MEDICAL ENTOMOLOGY 



EXERCISE 19b 



THE MITES 



CLASS ARACHNIDA, ORDER ACARINA, FAMILY SARCOPTID2E 



A. Characteristics of Sarcoptida. The legs are six-segmented, 

 short and thick, and terminate in a sucker or a slender bristle 

 ending in a disc-like sucker. 



B. Sat -copies scabei var. suis. This variety of itch mite in- 

 habits the skin of the domestic pig, tunneling its way through 

 the epidermis, causing a scaly appearance. This variety may 

 also attack man. 



a. Note the minute size of this species. How does it compare 

 with the poultry mite in this respect? 



b. How does it compare in color with the poultry mite? 



c. What is the form of the body and position of legs? 



d. Note the transverse rows of bristles on the dorsal surface of 

 the mite. 



e. Study the .terminal structures of the leg, noting especially 

 the spines and sucker (ambulacrum). 



Draw the specimen. 



EXERCISE 20 



OTHER MITES 



CLASS ARACHNIDA, ORDER ACARINA, FAMILY SARCOPTHXE (cont.) 



A. Psoroptes communis var. ovis is the scab mite of sheep, 

 producing scabies. Comparing this Psoroptic mite with the 

 Sarcoptic mites, notice the following characteristics: 



a. The body is elongate oval. 



b. All four pairs of legs appear beyond the margin of the body. 



