339 



(2), (3), and (4) form the piercing organ or 

 haustellum. 



5. The Palpi are four-jointed and form a 

 kind of sheath for the haustellum. The shape 

 of the palpi, their spines and processes are of 

 the greatest importance in classification. 



Fig. 76. Eggs, Larva, and Adult Tick. (After Maasen) 



6. The Scutum is a dorsal structure, situated 

 behind the base of of the rostrum. , It is a 

 hard leathery plate. In the male it practically 

 covers the whole of the dorsum. In the female 

 it is confined to a roughly triangular anterior 

 portion of the dorsum. The males are thus 

 readily distinguished from the females. It is 

 absent in the ' Argasidae. 



7. The Porose areas are dorsal structures 

 forming two oval depressions one on each side of 

 the middle line at the base of the rostrum. They 

 are most conspicuous in the female, but exist in 

 both sexes. 



8. The Eyes, not always present, are small, 

 almost globular structures, situated laterally at 

 the margin of the scutum in the Ixodidae, or as 

 punctiform structures on the supracoxal fold of 

 the first leg in the Argasidae. 



9. The Stigmata. — Situated ventre ' ' and 

 laterally behind the level of the fourth le; a the 



