372 ME. A. D. MICHAEL ON HYPOPI, 



de limagon. He noticed the singular moutli with two setae ; and, 

 in his list of genera, he put a query whether it was a larva; 



Dufour*, in 1839, added two species to Duges's genus ; one he 

 found living in closely packed groups on. the head and thorax of 

 Coleoptera of the genus Feronia, and these he called Sypopus 

 feroniarum ; the other he found upon Diptera of the genus Sapro- 

 mysa, and called Sypopus sapromysarum. He evidently regarded 

 them as specially parasitic upon the particular creature upon 

 which he found them ; he also instituted a new genus (Tricho- 

 dactylus) for an allied Acarid which he found parasitic upon bees 

 of the genus Osmia. 



C. L. Kocht, in 1843, admits the genus Hypopus; but in his 

 great wurlihe only gives one species, although, in his later work, 

 he transfers others to the genus, one of which clearly does not 

 belong to it. He also originated a third genus (Somopus) for 

 two creatures which he found upon field-mice and squirrels, and 

 which he at first classed among ZfermaleicJii, but which do not 

 appear to differ materially from Dufour's Trichodactylus. 



DujardinJ, also in 1843, found on the wing of a bee a small 

 mite for which he originated a new genus (Anoetus) ; this genus 

 he subsequently suppressed, finding it to be simply a Hypopus. 



Grervais§ next described a new species of Hypopus, which genus, 

 oddly enough, he joined to TyroylypJms, without having an idea 

 of the connexion subsequently ascertained to exist, and notwith- 

 standing the great apparent difference. It must be confessed 

 that he also joined to it other genera which have not any con- 

 nexion with it. 



Dujardin|| returned to the subject in 1847-1849; he then 

 made an elaborate study of Hypopus, and it struck him that all 

 the creatures mentioned above were immature forms and not 

 species at all ; it was the first time that this idea was put forward, 

 except Duges's query above mentioned. Dujardin called atten- 

 tion to the numerous ventral suckers which served the Hypopi 

 as means of attaching themselves to other creatures on which 



* Ann. Sci. Nat. 2e ser. t. xi. p. 278. 



t ' Deatschlands Orustaceen, Myriapoden und Arachniden ' : Regensburg. 

 (In Panzer's German Insects.) ' Uebersicht des Arachnidensystems ' : Niirn- 

 berg, 1839-43. 



|. Ann. Sci. Nat. 8<= ser. ZooL t. ii. p. 245. 



§ ' Suites a BuiFon ' : Apteres, t. iii. p. 280. 



II Ann. Sci. Nat. 3'= ser. Zool. t. xii. pp. 243-250. 



