OB LIFE-HISTOBT OF CEETAIN ACAEIKA. 375 



such exercises of imagination. He regards Sypopus, Homopus, 

 and TricTiodactylus as being all similar things, and as having the 

 power of remaining without any nourishment during the whole 

 period of their existence in this stage, and this view he supports 

 in a special paper on the subject*. 



In a subsequent memoirf, Megnin extends his view of the 

 nymphs of certain Acarina assuming a hypopial condition in 

 order to preserve the species under adverse circumstances, so as 

 to include the case of certain Acari found in the cellular tissue 

 of birds by Giuseppe GreneJ, Charles Eobertson§, Montagu||, 

 and Filippo de Filippi^, which the last-named writer called Sypo- 

 dectes, but which Megnin considers to be the hypopial nymphs 

 of feather-feeding Sarcoptidge {Fteroliclius falciger') . 



In one of his latest works** Megnin states that Dufour's ILypo- 

 pus feroniaruvi is the hypopial nymph of Tyroglyphus rosiro-ser- 

 ratus {Serrator ampliibius), Megnin, and that the Acarus spini- 

 tarsiis of Hermann is the same as Homopus elepliantis, Fiirsten- 

 berg, and is the hypopial nymph of the common Cheese-Mite 

 {Tyroglyphus siro}. He does not say how the last fact was as- 

 certained ; and in his memoir on Sypopus, above quoted, he states 

 Hermann's spinitarsios to be the hypopial nymph of his Tyrogly- 

 phus mycopliagus. 



Mr. Tatemff, in 1872, figured and described, under the 

 name of Acarellus mtisccs, a creature which is a Hypopus, and 

 which he is of opinion that lie took from the abdominal cavity of 

 a dead flea. 



Andrew Murray J J, in November 1876, entered vigorously into 

 the dispute. He does not seem to have made any personal ob- 

 servations, but he elaborately discusses almost all the above- 



* " Mem. siir les Hypopes," Journ. de I'Anat. et de la Physiol. (Eobin's), 

 t. X. p. 225 (1874). 



t " Les Acariens parasites du tissu cellulaire, &e., des Oiseaux,'' ibid. t. xv. 

 p. 120 (1879). 



I ' Erevi cenni su un Acaridio del genere dei Sarcopti che vive suUa Strix 

 flammea: ' Torino, 1848. 



§ Microseopical Journal, Feb. 1866. 



II Mem. Wernerian Nat. Hist. Soc. 1808, vol. i. p. 176. 



^ "Note zoologiclie 1. Hypodectes nuoTo genere di Acari di," in Archiv per 

 la Zool., r Anat. e la Fisiol. fasc. i. pp. 54-60 : Genova, 1861. 

 ** ' Les parasites et les maladies parasitaires ' : Paris, 1880. 

 ft Monthly Microsc. Jouru. 1872, p. 263, pi. xl. 

 \\ ' Economic Entomology, Aptera ' : London, 1877. 



