14 



Acarology 



2. Epiostracum — the upper layer 



3. Ectostracum — the middle layer, usually pigmented with acid dyes 



4. Hypostracum — the inner layer, usually pigmented with basic dyes 



Figure 6 A section through the integument of Hyalomma marginatum hrioni- 

 ciim Schulze and Schlottke, 1929 showing the two inner sclerotized layers, the 

 ectostracum and hypostracum, with the hypodermis beneath them. (After 

 Vitzthum 1940) 



The four layers are not recognizable in all acarinids. One or more 

 of the chitinous layers may be absent or so combined with others that 

 they are unrecognizable. In some cases the hypodermis itself may be 

 so expanded by swelling of the opisthosoma, such as occurs in Pye- 

 motes, that it is impossible to demonstrate it. 



Although the fundamental structure of the integument is similar in 

 all species, the appearance, texture, and physical properties of the 

 sclerotized coverings are varied and widely different from one group 

 to the next. The Notostigmata possess a leathery, thin, granular cuticle. 



Many mites are completely or par- 

 tially enclosed in heavy, armor- 

 like sheaths. The Holothyroidea, 

 many of the Mesostigmata, and 

 the majority of the Oribatei are 

 provided with hard, protective 

 plates that enclose the entire 

 body. The Trombidiformes and 

 the Acaridiae have an elastic, 

 transparent cuticle that may have 

 hardened regions in the form of 

 plates or setal bases. 



Much of the beauty of form 

 and design resident in the struc- 

 ture of the Acarina is to be found 

 in the ornamentation of the cuti- 

 Figure 7 The sternal plate of the ^j^ ^^-^^ -^ produced by pores, 

 nymph of Parasitiis fuconim (De- ^ \ 



Geer), 1778. (After Vitzthum 1940) Tidges, folds, or pigment found 



