142 



GENERAL ZOOLOGY 



legged forms. The mouth parts are more or less united 

 to form a beak for sucking blood. They live as parasites. 



Fig. 79. Harvestman. (Natural size) 



Ticks in Relation to Disease. Almost everyone who spends 

 any time in the woods has had the experience of finding a 

 small brown creature firmly attached to his skin, rapidly 



A B 



Fig. 80. Cattle tick. (Enlarged) 



A, male tick ; B, female filled with blood from host. (From the United States 



Department of Agriculture) 



gorging itself with blood. This is the common wood tick. 

 The species found in the eastern part of the United States 

 is practically harmless. A closely related species (Derma- 

 cen'tor venus'tus) in the northwest of our country carries 



