66 HELMINTHOLOGY 



The following examples of insect larvae should be studied care- 

 fully, counting the number of body segments, noting the presence 

 or absence of special prehensile booklets, and other external 

 characteristics. Draw a specimen of each. 



A. Types of insect larvae. 



a. Larvae of the horse botfly, Gastrophilus equi; habitat, 

 stomach of equine animals. 



b. Larva of the ox warble-fly, Eypoderma lineata, causing 

 what is commonly called "grub in the back" or warbles; habitat, 

 the deeper layers of the skin of bovine animals. 



c. Larva of the head maggot fly, (Estrus oms; habitat, nasal 

 sinuses of sheep and deer. 



d. Larva of the warble-fly of rabbits, Cuterebra cuniculi; 

 habitat, deeper layers of the skin of rabbits and other rodents, 

 commonly found in the neck. 



e. Larva of the screw worm fly, Chrysomyia macellaria; 

 which is commonly found in wounds and open sores of domesti- 

 cated animals. 



f. Larva of the common blowfly, Calliphora wmitoria, a 

 flesh fly and scavenger. 



g. Larva of the common housefly, Musca domestica. 



B. Examine a dissection of a fly larva under both low and 

 high power objectives, noting the tracheal system, an intricate 

 series of tubules ramifying through all parts of the body. Draw 

 several tracheae. 



C. Describe points of difference noted between worms and 

 larvae. 



EXERCISE 38 



ANTHELMINTHICS 



While the main object in the present work is to prevent infec- 

 tion, the student should nevertheless be familiar with the com- 

 moner agents used to destroy and expel internal parasitic worms. 



