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the hyposternite of Robin. It consists of three portions, the outer and inner 
rings, and the lateral rod. Of these the outer ring (or) is the largest, and at 
its posterior end is articulated with the hammer head. Part of the concavity 
Fig. 17. Sarcoptes scabiei var. equi. Male genitalia seen from below. The structures behind the 
genital apron are not drawn, though actually the apron is quite transparent, eal, limbs of 
the epiandrium; ga, genital apron; hh, hammer head; Ir, lateral rod of hyposternite; mea, 
medial epiandrial rod; V 5, fifth ventral seta, without counterpart in the female. 
Fig. 18. Sarcoptes scabiei var. equi. Epiandrium as seen after removal of genital apron, bp, basis 
penis; ea, epiandrium; eal, its limbs; hh, hammer head; hn, hyposternite; ir, inner ring; 
is, intromittent spicules; Ir, lateral rod; mea, median part of epiandrium; or, outer ring. 
of the outer ring is filled by the inner ring (ir), which is intimately connected 
with the outer and lies on its dorsal surface. Through the most anterior part 
of both outer and inner ring passes a tubular passage (shown in dotted line 
