Acarina. Acari. Mites. Ticks. 115 



2. Body. The body has distinct generic or specific characters 

 on its dorsal and ventral surfaces and on its margins — lateral, 

 anterior and posterior. 



Dorsal Structures. These include dorsal shield, eyes, porose 

 plates, postero- marginal festoons and shields, furrows, pits, puncta- 

 tions and hairs. 



Dorsal Shield {dorsal plate, thoracic shield, scutum. ) This is 

 a hard chitinous plate found in the Ixodidae and wanting in 

 Argasidae. In males it covers all or nearly all the dorsal aspect. 

 In nymphs it covers the anterior half or more. In adult females 

 it is restricted to a small anterior portion of the back. Usually 

 notched anteriorly to receive the head it shows at each side a 

 prominent forward projection. It shows a variable number of 

 pores (punctations) with or without hairs. 



The eyes are two small, semiglobular objects placed one on 

 each lateral margin of the scutum in Ixodidse ; or in pits on the 

 supracoxal fold near legs I in Argasidse. 



The porose plates are placed one on each side of the median 

 line about opposite legs III and IV in Rhipicephalus, Boophilus, 

 Dermacentor and Hyalomma. They show a number of wart-like 

 elevations each bearing on its summit a pore in form of a slit. 



The postero-marginal festoons are only present in certain 

 species like Dermacentor and Amblyomma, which have eleven 

 each. 



The Dorsal Furrows caused by contractions of the dorso- 

 ventral muscles, vary in the same individual at different times 

 and may be obliterated by repletion with blood. 



Pits, punctations, hairs and spines may be made out by 

 the aid of a good hand lens. The pores are of varying size, give 

 passage to hairs or spines and lead to gland tissue beneath. 



Ventral Structures. The ventral aspect presents : Genital 

 pore, anus with anal valve, anal shields, ventral shields, 

 stigmata, furrows or grooves, pits, punctations, hairs 

 caudal appendage and legs. 



The genital pore is a transverse slit crossing the median line, 

 between the first three pairs of legs. It is wanting in the hexa- 

 pod larvae. 



The Anus is between the last pair of legs, in the median line 

 and surrounded by a chitinous valve. 



