HYPOPIDjE. 247 



CA^E Acarellus muscse, which he took from " the abdominal cavity of a 

 xi\'. ' 



dead flea." Qu'allait-il faire dans cette galere, if it was a phase 



of a vegetable-feeding Tyroglyphus j neither could there be any 

 question of development between a flea and a Hypopus. But it 

 was a very natural place if the creature is an internal parasite. 

 Again, Dr. Maddox (Monthly Micr. Journ., 187 1) describes and 

 figures a Hypopus that he obtained from a bat's ear, that was 

 swarming with the larvae of a parasitic tick that we have already 

 and shall again have occasion to speak of If a phase of Tyro- 

 glyphus, it could hardly have mistaken a bat's ear for its natural 

 food, a hyacinth bulb. If a parasite, it might very naturally be 

 found among the ticks on which it preys ; and what adds value to 

 these two observations is that they were both made by observers 

 who appear to have made no special study of the Acarids and 

 who were ignorant of Hypopus and its points of interest. Mr. 

 Tatem supposed that his Acarellus might perhaps have something 

 to do with Phytoptus, and Dr. Maddox goes no farther than to 

 call his a single minute insect found free amongst the hairs along 

 with specimens of the other mite he there found and adds "(? im- 

 mature male)": — but the figures given by both Mr. Tatem and 

 Dr. Maddox are unmistakably Hypopi. It is also not irrelevant 

 to remind the reader of Dujardin's observations regarding a 

 Hypopus found on or in connection with a parasite of the field- 

 mouse, which, from his description, is doubtless Myobia musculi ; 

 and to add that a careful examination of the description of Dr. 

 Maddox's mite found in the ear of a bat, has satisfied us that its 

 generic place is not with the Pteropti, but with the Sarcoptidae, 

 and next to Myobia musculi. 



Another circumstance observed by M. Megnin in his study 

 of the Tyroglyphi and Hypopi, the successive disappearance 

 of Tyroglyphi, appearance of Hypopi, and re-appearance of 

 Tyroglyphi in his boxes, suggests the remark that, on our hypo- 

 thesis, it presents none of the difficulties of explanation which 

 attend it on his. On the mushrooms becoming dry in his cage 



