318 Miscellaneous. 



under the name of Anoetus, an Aearus found by Dr. Manceau de Cha- 

 labre upon the wing of a bee, has been led to extend his researches 

 to several allied species, and he has recognized that they ought to be 

 united with Tlypopus ; i. e. that they, like his Anoetus, have neither 

 a mouth nor a digestive apparatus ; also that they are provided with 

 suckers upon the posterior part of the abdomen, and that these 

 suckers merely serve to fix them at their will, in readiness for their 

 last metamorphosis, which is effected at the expense of the internal 

 nutritive matter which they have received at their birth. 



In 1847, M. Dujardin first found, mponMusca stabulans of Fallen, 

 a Hypopus in the same state as the Aearus muscarum of Degeer, and 

 it was in the case of this Aearus, which was Y^^^yths of a millimetre in 

 length, that he was enabled to determine the absence of the mouth 

 and intestine. Since then, he has found other species upon Sta- 

 phylini and Cryptops, but having the same organization ; lastly, in 

 September 1849, he found some upon a fern, Ceterach oficinarum, 

 among which there were a certain number of shells or teguments ; 

 these were perfect, but empty, transparent, narrower, and consequently 

 more like those which he had seen upon the wing of the bee : the 

 greater number were living, and continued to live in water ; and the 

 power with which these Acari are able to fix themselves to a plate of 

 glass was then noticed. Some of them, which were few in number, 

 and had become immoveable, exhibited through their integument 

 another form of Aearus which filled the whole of its internal cavity, 

 and which were furnished with a mouth, having at the same time 

 palpi and chelicera like the Gamasi and the Bermanyssi which live 

 in great numbers in the same situation. From that time it became 

 evident that the Hypopi, which had no mouth, nor any possible 

 mode of growth, and which lived fixed upon polished surfaces that 

 could yield them nothing— it was evident, shall we say, that these 

 Hypopi are the larvae, or rather, if we may use the expression, the 

 ova furnished with feet, in the interior of which, without any food 

 derived from without, the young Gamasus is formed, solely at the 

 expense of the contained substance. 



Consequently, M. Dujardin has been enabled to search for and find 

 other Hypopi upon all the insects infested by the Gamasi, such as 

 the Geotrupidce, the Neerophoridce, the Humble-bees, &c. They are 

 most commonly found at the base of the abdomen, or beneath the 

 first rings, or in the anfractuosities of the metathorax ; but judging 

 from the diversity of their forms, we should think that there would 

 be different species of Gamasi, or Dermanyssi, or even Uropodi. Other 

 species have been found by beating the branches of trees ; and lastly, 

 one species, which is very remarkable by its method of fixation, has 

 been found upon subterranean rodents (Arvieo/a siibterranea), upon 

 which also the Gamasi are parasitic. The latter Hypopus, in fact, 

 would not have been able to fix itself upon the hairs or upon the skin 

 by the suckers ; hence it is furnished, beneath the upper part, with a 

 pair of striated lobes or tubercles, which becoming approximated like 

 two lips, firmly embrace the single hairs of the mammifer. 



In short, the Hypopi are Acari with eight feet, without either 

 mouth or intestine, and which, being deprived of all means of alimen- 



