126 Sarcoptes 
investment of the basal part of the basis capituli is in some places thickened 
into bands which act as mechanical stays. The exact disposition of the bands 
on the ventral surface can be seen in Fig. 10. They support the base (b 1) and 
sides (b 2) of the organ; at its posterior extremity the bands b 1 unite at the 
middle line to form a rounded mass of chitin (z), the “menton” of Robin. 
The first epimere (el) is in close relation to the side (6 2) of the basis capituli, 
but there is no articulation between them. Similar bands pass from the sides 
towards the middle line on the dorsal surface (b 3, Plate VII), and also on the 
Fig. 7. Sarcojptes scabiei var. eqai. Capitulum of adult female seen from below after removal from 
camerostome. b 1, 2, 3, 4, bands of chitin forming supports for the basis capituli; C 2-4, 
capitular setae; ch, chelicera; ck, cheek-piece; k, keel; kn, knob of chitin, the maxilla of 
Robin; ll, lower lip; z, part of the thicker chitinous skeleton of the basis capituli, the 
“menton” of Robin. 
ventral (b 4). The inner end of b 4 meets the longitudinal b 5 to form a rounded 
heavily chitinized knob (kn). On the mid-ventral line there is a minute keel 
(k) projecting downwards. 
The transverse bands b 3 on the dorsal, b 4 on the ventral side, divide the 
basal third of the basis capituli from the rest. From b 4 springs the cheek- 
piece (ck), a triangular plate of the thinnest and most colourless chitin, which 
covers the palp ventrally and laterally. This cheek-piece is so transparent 
that one has difficulty in seeing it when it is folded close about the palp. In 
