DISEASES OF BEES 
279 
little interest to the lay reader, we have not 
yet learned very much regarding its life 
and habits. The fully grown egg-laying fe¬ 
male, the largest of the species, is about 
1/130 of an inch in length. She lays eggs 
singly, at intervals, which almost immedi¬ 
ately after deposition are larger than her¬ 
self, and where a few of such females are 
present in the air tubes of a bee, these 
early become packed with rows of sausage¬ 
shaped eggs. Erom the egg there emerges 
a six-legged young form or larva, which 
in turn becomes transformed into an eight¬ 
legged immature adult. The adult female 
alone of all the forms possesses a breath¬ 
ing system similar to that of the bee itself, 
but with a smaller number of spiracles. 
She is a tracheate mite, while her mate 
breathes thru the general surface of his 
body. The male Tarsonemus is the small¬ 
est of all the forms and is not usually 
larger than 1/230 of an inch. It seems 
likely that the pairing of the mites takes 
place within the bee, and that subsequently 
the fertile females migrate to the outside 
and enter fresh hosts. These mites thus 
do not appear normally to exist apart 
from the bee for any great length of time. 
They are true parasites, breeding and in¬ 
creasing in numbers within it, feeding upon 
its blood, which they do by piercing with 
needle-shaped mandibles the breathing 
tubes, and imbibing the surrounding blood. 
This repeated pricking maintains a con¬ 
tinued irritation in the walls of the tra¬ 
chea, which results in their becoming thick¬ 
ened, blackened in color, and brittle in tex¬ 
ture. The air supply is impeded and viti¬ 
ated by the crowds of parasites, and it 
has been a matter of surprise to us to find 
that bees are able to work and live as 
long as they do whilst harboring these 
parasites. It is the disorganization of the 
colony, resulting from the prolonged in¬ 
fection of large numbers, which is the es¬ 
sential crisis in this disease, rather than 
the actual mortality amongst the bees, 
which may be a long-delayed event. 
“In the course of the investigations at 
present in progress, thousands of individ¬ 
ual bees have been examined during the 
last nine months. In every stock suffering 
from Isle of Wight disease, Tarsonemus 
woodi has been found in every sick mem¬ 
ber of these. These examinations covered 
bees taken from diseased stocks in all the 
years from 1916-1921. One of the most 
important discoveries has been that for 
some time before the disease becomes ap¬ 
parent to the beekeeper thru the familiar 
crawling symptoms, there may be a quite 
high proportion of infected individuals in 
the stock; bees foraging and carrying pol¬ 
len or nectar have frequently been found 
in this condition, both in stocks showing a 
proportion of “crawlers” and in stocks 
supposed to be healthy. 
“Such discoveries admitted of at least 
two possible interpretations. It might be 
that Tarsonemus woodi was not causally 
connected with Isle of Wight disease, but 
was merely a common and comparatively 
harmless inmate of the bee, or one which 
became established in an otherwise smit¬ 
ten bee. It may be mentioned that ap¬ 
pearances within infected bees are very 
much against such a view. On the other 
hand, there was the possibility that some 
time might elapse after infection was es¬ 
tablished in a stock, while the mite brood 
was slowly increasing in numbers, during 
which the infected bee was able to continue 
working. There would thus be a period 
of infection in which the presence of the 
disease was unsuspected by the beekeeper, 
because the bulk of the bees continued to 
work, a period of small undetected losses, 
whilst all the time the proportion of in¬ 
fected bees was mounting up within the 
stock. Results have shown that the de¬ 
gree and rate of infection within a stock 
depend in some measure upon the continu¬ 
ance of fresh infections from the outside, 
as well as upon other factors which need 
not here be discussed in detail. The real 
test lies in the continued observation of 
such stocks, and in all of those which have 
been under our observation, with the ex¬ 
ception of a very few cases not yet ac¬ 
counted for, the familiar symptoms of the 
disease eventually developed and the stock 
died out. More convincing evidence could 
not be obtained, and I regard the proof 
that Tarsonemus woodi is causally related 
to Isle of Wight disease as virtually com¬ 
plete.” 
A careful reading of the two papers 
seems to show that the real cause of the Isle 
of Wight has been discovered. It is en¬ 
couraging to know that so far the authori- 
