THE INSECT STING 35 



c. The third pair of legs is devoid of ambulatory suckers, and in 

 their place note a long pair of bristles for each leg. 

 Draw a female specimen. 



B. Psoroptes communis var. boms is the mange mite of the ox. 

 a. Can you find any perceptible difference between this 



species and the one above? 



C. Psoroptes communis var. equi is the mite which causes 

 humid mange of the horse. 



a. The rostrum is characteristically long, twice as long as 

 broad, otherwise the species differs but imperceptibly from the 

 species above. 



D. Sar copies scabiei var. canis is one of the mange mites of 

 the dog. 



a. Notice similarity to the variety inhabiting swine. 



E. Sarcoptes mutans is the parasite which causes scaly leg 

 in poultry. 



Examine a bit of mounted scrapings from the leg of a hen 

 affected with scaly leg. The circular mites (typically Sarcoptic) 

 are easily visible. 



Draw the specimen. 



EXERCISE 21a 



THE INSECT STING 



The insect sting, as found in the Hymenoptera (bees, wasps 

 and ants) is a modified ovipositor, the function having been 

 changed from that of an egg apparatus to that of a defensive 

 weapon. In many insects the sting still serves both purposes. 



A fresh worker bee should be used for study; these can usually 

 be procured at a nearby apiary, or bees may be killed hi the 

 field just before using. 



With a needle remove the last evident scale-like segment of 

 the abdomen, which will bring with it the sting, the venom sac 



