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ARTHROPODA 



Classification. — The order Acarina is divided into the following 

 suborders: — 



Suborder Notostigmata. — -Acarina in which the opisthosoma 

 is segmented by ten integumental grooves, of which the anterior 

 four are furnished with a single pair of dorsally placed spiracles. 

 (Family : Opilioacaridae.) This suborder does not concern us. 



Suborder II. Cryptostigmata. — Acarina with a hard integu- 

 ment strengthened by chitinized dorsal and ventral sclerites. 

 Stigmata on the acetabula of the third, fourth, fifth, and sixth 

 pairs of appendages. (Family: Oribatidse.) This also does not 

 concern us. 



Suborder III. Metastigmata. — Acarina with a hard integument 

 like the Cryptostigmata. One pair of stigmata above and behind 

 the base of the fourth, fifth, or sixth pair of appendages. 



Superf amily A : Gamasoidea. 

 Superfamily B : Ixodoidea. 



Suborder IV. Prostigmata. — Acarina with soft integument 

 strengthened by special sclerites, those on the ventral surface of 

 the prosoma apparently representing the basal segments of the 

 legs embedded in the skin. Except in the aquatic species, there 

 is a pair of stigmata close to or above the first pair of appendages. 

 Superfamily A : Trombidoidea. 

 Superf amily B : Eupopoidea. 



Suborder V.AsTiGMATA. — Degenerate Acarina, mostly parasitic, 

 like Prostigmata in the development of integumental sclerites and 

 the softness of the skin, but with the respiratory system absent. 

 (Superfamily: Sarcoptoidea.) 



Suborder VI. Vermiformia.— Degenerate parasitic Acarina 

 without respiratory system, and with the body produced posteriorly 

 into an annulated caudal prolongation. With the third, fourth, 

 fifth, and sixth pairs of appendages short, and only three jointed. 

 (Family: Demodicidae.) 



Suborder VII. Tetrapoda. — Degenerate atracheate Acarina 

 with body as in the Vermiformia, but with the third and fourth pairs 

 of appendages long and normally segmented, and the fifth and 

 sixth entirely absent. (Family: Eriophyidae.) This suborder, 

 however, need not concern us. 



SUBORDER III. METASTIOMATA. 



The parasites included in this suborder would in popular language 

 all be called ticks. 



It is divided into two superf amiUes :— 



A. Gamasoidea. — With a small hypostome without teeth. 



B. Ixodoidea.- — With a large hypostome armed with many 

 recurved teeth. 



SUPERFAMILY A: GAMASOIDEA. 



Tile superfamily Ciamasoidea is divided into three families: — (i) Dermanys- 

 sidse, (2) Uropodidae. (3) Gamasidae. 



