114 BEIT1SH TYEOGLYPHID2E. 



every step the creature takes ; they certainly, in some 

 species, possess sensory papillse on the distal end of the 

 organ. There is some reason to suppose that the sense of 

 taste does to some extent reside in the palpi, which are 

 particularly active when food is being sought or con- 

 sumed ; but nothing is definitely known on the subject. 



As regards the sense of sight the Tyroglyphidae are 

 usually without eyes or any organs which can be looked 

 upon as optic ; but there is one known species, and one 

 only, where the eyes exist in all stages from larva to 

 imago, and may be plainly seen ; this species is Carpo- 

 glyphus anonymus, which possesses a pair of simple 

 eyes on the anterior margin of the cephalothorax ; 

 which are more conspicuous in the larvae and nymphs 

 than in the adults, but are plainly visible in all ; they 

 resemble the ocelli of insects. These organs were first 

 pointed out by Kramer,* but appear to have been 

 overlooked by all subsequent writers except Nalepa, 

 who says that they consist of a moderately arched 

 cornea and a refractive lens beneath it; he was not 

 able to trace the optic nerve. 



No other organs of special sense are at present 

 known in the Tyroglyphidas. 



THE EXPULSOEY VESICLES OE OIL-GLANDS. 



On each side of the hinder part of the abdomen, in 

 most if not all of the Tyroglyphidse, is a vesicle often 

 of considerable size, usually containing highly re- 

 fractive fluid ; which is sometimes colourless, sometimes 

 yellow or brown ; it is generally placed on the actual 

 side of the body where the abdomen is thick in a 

 dor so -ventral direction ; often more dorsal in position 

 where the abdomen is very flat, or comes to a sharp 

 edge laterally, as in some Hypopi. It must be con- 

 sidered a dermal organ ; it immediately underlies the 

 skin, and its chitinous layer is cast with that of the 



* " Ueber die posteinbryonale Entwicklung bei der Milbengattung 

 Glycuphagus" in 'Arch. Kaiurg.,' 1880, Jalirg. xl, Bd. i, pp. 102110. 



