( 768 ) 
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 (1892). 
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 — Tarsonemidse and Scutacaridse * (Oudemans, 1916). This last is 
the Disparipedidse 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 desire here to gratefully acknowledge the courtesy of Dr Oudemans in guiding me to the literature of the 
Tarsonemidee and Acarina generally. 
