278 
DISEASES OF BEES 
Great Britain, there is, of course, danger 
that it may spread to other countries thru 
the importation of queens or bees from the 
British Isles. 
For many years the cause of this disease 
was unknown. In 1912 and 1913 it was be¬ 
lieved that it was due to a protozoan, Nos- 
ema apis; and this view was held until 1920, 
when Drs. Rennie and White, and Elsie J. 
Harvey of Great Britain (particularly the 
last named), discovered that the primary 
cause was not due to a protozoan or a bac¬ 
terium, but to a parasite or a mite, Tarso¬ 
nemus woodi. This parasite, according to 
their paper, published in the Transactions 
of the Royal Society of Edinburgh, Yol. 
LII, Part 4, attacks the bees thru the 
breathing orifices. To quote exactly it 
“occupies a very restricted region in that 
part of the tracheal system which has its 
origin at the anterior thoracic spiracle. In 
a well-established case of infection it will 
be found that, extending inward from this 
spiracle on either side indifferently, para¬ 
sites in all stages of development may be 
present in any part of this portion of the 
respiratory system, whilst the ill effects of 
their presence may be seen not only in the 
region of occupation but in the muscular 
tissue to which these extend. It is not an 
infrequent occurrence in advanced cases of 
the disease for these wider tracheae to be 
occupied by mites in closely packed forma¬ 
tion. All stages of development occur; 
e. g., ova, larvae, nymphs, and adults may 
be found together. In the smaller branches, 
frequently these are occupied as far as 
their diameter will permit, when a single 
individual may be found practically block¬ 
ing the tube, and sometimes a linear suc¬ 
cession of individuals may be seen in such 
a position. * * * Tim primary para¬ 
sitic invasion takes place thru one or both 
of the first pair of spiraeular orifices, and 
apparently thru these alone.” The infec¬ 
tion may be on one or both sides. Quoting 
again: “A single mite may enter the bee, 
or several may enter together or at inter¬ 
vals. * * * It is usually only during 
the latter stages of attack that the mite 
attains the smaller tracheae, the thoracic 
air-sac, and the vessels of the head.” 
In speaking of bees obtained from Italy 
and elsewhere, Dr. Rennie says: “In all, 
several hundreds of bees were obtained 
from this source. These, along with others 
obtained direct from Italy, were searched 
for the presence of Tarsonemus. The re¬ 
sult of these examinations was that the 
bees were found entirely free from the 
parasite. The evidence is so far satisfac¬ 
tory that it may be accepted that Tarsone¬ 
mus is not being introduced to this country 
in Italian bees. Smaller numbers of Dutch 
bees so imported have also yielded on ex¬ 
amination a similar result. Bees in limited 
numbers have also been obtained from 
Switzerland and from North America, all 
i of which were also free from this para¬ 
site.” On the question of whether bees in 
England are more susceptible to this dis¬ 
ease, Dr. Rennie says again: 
“It has been suggested that British bees 
of the present time are of a deteriorated 
breed, and have lost resisting power, so 
that Tarsonemus, a relatively non-patho- 
genic parasite ordinarily, is able to breed 
excessively. My provisional answer is that 
other racial forms are relatively affected. 
For example, Egyptian, Dutch, Punic, and 
Italian bees can be readily infected, and in 
these Tarsonemus multiplies with disastrous 
results, as in British bees. But the ques¬ 
tion of the ability of a stock to survive a 
prolonged period of Tarsonemus infection 
is not a simple one. Amongst other fac¬ 
tors it involves the question of relative fer¬ 
tility of particular queens, as well as that 
of individual tolerance of the parasite.” 
In a later paper published in the Report 
of the Aberdeenshire & Kincardinshire 
Beekeepers’ Association for 1920, pages 
19-21, Dr. Rennie goes somewhat more into 
details as follows: 
“The organism now known to science by 
the name of Tarsonemus woodi, n. sp.—to 
give its full description—which is invari¬ 
ably present in bees suffering from Isle 
of Wight disease, is a soft-bodied, bean¬ 
shaped, scantily haired, colorless, eight¬ 
legged creature, invisible to the naked eye. 
It belongs to the class, Acarina, and ranks 
amongst the tiniest of a group of animals 
whose popular title serves in our language 
as a common term to indicate excessive 
smallness. This particular mite, tho one 
of the minutest of its class, has a complex 
organization, and has much in this respect 
in common with the bees themselves. Be¬ 
yond a knowledge of external detail, of 
