248 ARACHNOIDEA. 



CASE (which shews an insufficiency of moisture for the wants of the 



XIV. 



Tyroglyphi), they disappeared, that is, dried up and died. On 

 the death of an insect containing parasites, these latter usually, if 

 they can, make their way out and anticipate their period of pass- 

 ing into the pupa state ; so here on the death of the Tyroglyphi 

 the Hypopi made their way out, but only to die ; — " they rested 

 inert on the walls and as if deprived of life." He never says that 

 they revived, but he says they disappeared on (but it does not 

 follow that it was in consequence of) fresh mushrooms being 

 introduced into the cages. Our understanding of this would be 

 that they had really died when they seemed deprived of life. But 

 fresh swarms of Tyroglyphi now succeed them. Why not ? There 

 might still be plenty of Tyroglyphi living to replenish the stock 

 now that fresh food was introduced; for in speaking of their 

 first disappearance, he does not say that they wholly disappeared, 

 but "disappeared in great part." But besides this, in introducing 

 fresh mushroom-food, even with every care to exclude eggs or 

 Acari, there is always a great chance of their getting admission in 

 spite of every precaution. 



Further, if our hypothesis be right, it helps to explain how 

 Claparede and others have failed to find any six-footed larvae of 

 Hypopi going about free. At that stage we assume them to be 

 in the inside of other insects. Other puzzling points in the 

 economy and life-history of these creatures still remain awaiting 

 elucidation. As yet no sexual organs have been found in them, — 

 which, so far as it goes, is a point in favour of M. Megnin as 

 indicating immaturity and progress of development. 



Again, what are the great clusters of them that are seen ad- 

 hering to other insects, doing there ? They are not on the insect 

 for purposes of feeding, for they have no mouth, or if they had, 

 they could extract nothing out of the polished armour of such 

 insects as the Histeridse, to which they cling. They cannot be 

 there for the purpose of laying eggs in the insect's body, even 

 supposing that mature males and females are there, although no 



