DEVELOPMENT AND IMMATURE STAGES. 163 



the well-known authority upon ants and the creatures 

 found in their nests.* For more than thirteen years 

 Wasmann had observed the presence of Hypopi in the 

 various nests of ants which he kept for observation ; 

 he found numerous other Acari, etc., in ants' nests, 

 and these formed the subject of a paper by Monier t 

 to whom Wasmann submitted his collection. Amongst 

 the Acari was a Tyroglyphus which was new to science, 

 and which Monier named T. Wasmanni ; this appears 

 to be a true myrmecophilous species, never having 

 hitherto been found except in ants' nests as far as we 

 know; while there it is in great numbers when the 

 Gramasidse which are found there, often in abundance, 

 do not eat it up. It was found in artificial nests of 

 Gamponotus Ugniperdus and Formica sanguined at 

 Prague in 1891 and in those of F. sanguinea-fusca and 

 in natural nests of Lasius fuliginosus at Exacten 

 (Holland). By some accident Monier described the 

 hypopial nymph of this species as that of T. Krameri, 

 which it greatly resembles, and described that of 

 Hist/iostoma rostro-s erratum as that of T. Wasmanni ; 

 but Monier had only spirit specimens to judge by and 

 it was hardly possible to do so correctly from them. 

 Later Wasmann sent me living specimens and I was 

 able to rear the Hypopi to the adult condition and 

 ascertain that what was supposed to be the Hypopus 

 of T. Krameri was really that of T. Wasmanni. 



With regard to the number of Hypopi, Wasmann 

 says that fifty upon one ant was a small number, and 

 that in badly infected nests hundreds, or even thou- 

 sands, might be found upon one ant. Wasmann 

 agrees that the Hypopi do not derive any nourishment 

 from the ant ; nevertheless they generally eventually 

 kill it simply by adhering to it in such immense 

 numbers. The essentially cleanly ants are unable to 



* " Ueber einige myrmecophile Acariden," in ' Zoo]. Anz ' 1897, Nos. 

 531,541, pp. 347 350. 



t " Memoire sur quelques Acariens et Thysanoures parasites on 

 commensaux des fouvmis," in ' Rev. biol. Nord France/ t. iv, 1892, pp. 

 376389. 



