180 (DU. A. C. OUDEMANS) NOTES ON ACARI. 



the ûrst pair of legs in the males (fig. 4) has a special function. 

 Its form is like that of the tactil or olfactory hairs of Tyrogly- 

 phina, but its insertion in a hard chitinous ring remembers me of 

 * the auditory organ in Ixodei , both discovered by G. Haller, Most 

 probably its function is to discover the other sex. 



But most probably again this is a necessary result of its aquatic 

 habits, for — and this is a vei^ striking fact — 1 did not dis- 

 cover this organ in three other species of Oppia, which fell into 

 my observation , and all are living in the air , viz. Oppia sp. , 

 Oppia bipilis Herm. , and Oppia exilis Nie. 



The tracheae are normal, notwithstanding the animal's aquatic 

 habits; consequently the animal must come from time to time to 

 the surface of the water. 



The 6 to 8 well developed eggs when still in the ovarial tubes , 

 measued 0.135 millimeters in length and 0.08 in breadth. 



Ä nympha of Cepheus sp. 



In fig, 9 I have figured the remains of a nympha of a Cepkeus 

 sp. , found by me in decaying leaves in Lochem, Aug. 1895. The 

 larval skin and the first nymphal skin are absent , only the second 

 and the last nymphal skin remain. The nymphal skins bear on 

 their edge 18 flat light brown coloured appendages. Each appen- 

 dage, except the two foremost pairs, bears itself a transparent 

 lanceolated, movable, leaf-Uke appendage or hair, which shows 

 nerves (fig. 13). 



These nerves are hollow and end in open holes (seen with oil- 

 immersion). Are these canals the endings of a circulatory , neph- 

 ridial, exsudating or breathing apparatus? In my dead nympha I am 

 unable to loose this pi'oblem, but certainly they have any function. 



The nympha of Cepheus [Tegeocranus) latus Koch has, if Mi- 

 chael's figure (Brit. Orib. I, tab. XIX, fig. 2) is right, not such 

 transparent colourless movable leaf-like hairs with a system ot 

 canals , but only feathered hairs , which have nearly the same 

 appearance as the two hairs of our present nympha , one of which 

 is represented in our fig. 12 (see below). In fig. 14; I have copied 



