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XXIX. 



(4) Isle of Wight Disease in Hive Bees — Acarine Disease : The Organism asso- 

 ciated with the Disease — Tarsonemus woodi, n. sp. By John Rennie, 

 D.Sc. (With One Plate and Two Figures in the Text.) 



(Read November 1, 1920. MS. received November 27, 1920. Issued separately March 25, 1921.) 



The organism which has been found living in the anterior tracheal system of 

 hive bees, and whose presence is associated with Isle of Wight disease, I have 

 identified as a hitherto undescribed species of the genus Tarsonemus. This 

 genus was founded in 1876 by Canestrini and Fanzago, and since then a moderate 

 number only of species has been established. The true systematic position of 

 these Acarines has been much in doubt, and their position in the order has 

 from time to time been revised. Canestrini (1888) constituted the Tarsonemes 

 the type of a special family, the Tarsonemini ; they have been associated with 

 the Oribatidse by Berlese, and with the Cheyletidse by Trouessart (r892). 

 Banks (1904) regarded them as showing resemblances to the Tyroglyphidse, and 

 placed them in a super-family Sarcoptoidea. An important character of the 

 Tarsonemes is the existence of a tracheal system in the adult female, which is 

 not found in the male nor in any pre-adult stage of either sex. This feature was 

 adopted by Berlese (1897) as the basis of his sub-order, Heterostigmata, and 

 by Oudemans (1906) in his division Trachelostigmata. This super-family includes' 

 two families — Tar.sonemidae and Scutacaridae * (Oudemans, 1916). This last is 

 the Disparipedidae of Berlese. 



The Tarsonemidse are a small family of soft-bodied mites, the females of 

 which are tracheate, and which usually exhibit prominent hairs upon the tarsi 

 of the last pair of legs. The body is more or less clearly segmented dorsally. 

 The mandibles are needle-like, the palps slender and minute. The females 

 possess in most instances, between the first and second pair of legs, a pair of 

 delicate rounded or club-shaped organs which have been designated pseudo- 

 stigmata by Oudemans. The legs are short, with six or fewer joints. They 

 are bedecked with a limited number of stout hairs, and terminate in claws. The 

 tarsi of the first pair possesses a single claw, the second and third, two. The 

 fourth tarsus varies in the different genera. Suckers are frequent. There may 

 be distinct sex dimorphism, especially in the genus Tarsonemus. 



The Genus Tarsonemus. 

 Canestrini's original description defining the genus is as follows : — 

 " Rostro normale e libero. Zampe del quarto pajo nella femmina poco sviluppate, 

 sfornite di uncini e di ventosa e terminate da duo setole ; zampe del primo pajo, 



* I de.sire here to gratefully acknowledge the courtesy of Dr Oudemans in guiding me to the literature of the 

 Tarsonemidse and Acarina generally. 



