9 
infected stock, in the final stages of the disease, may become 
infected by the female parasite at the age of six days, and 
that the second generation appears twelve to fourteen days 
later. As migration of the parasites does not occur to any 
serious extent until the trachea becomes congested, and as 
this will not occur within 14 days of the hatching of the 
second generation of parasites, the danger of serious 
migration will not arise until say 35 days have elapsed since 
the original infection. That is to say that in the case of a 
stock of which only a low percentage of its members are 
infected the spread of the disease within the stock will not 
become serious until the bees originally infected have 
reached the age of 5 weeks. 
If these infected bees, are removed from the sphere 
of action before they attain this age, the disease will not 
increase within the colony, but will gradually diminish and 
finally disappear. 
The main object of the method of treatment is 
therefore the elimination of the older members of the in- 
fected colony: this can be carried out in two ways: — 
(1). By wholesale isolation of these bees by artificial 
swarming and collection of the adult bees on 
the old stand. 
(2). By so greatly increasing the work of these adults 
‘as to appreciably shorten their lives. This is 
best effected by intensive brood production 
stimulated by feeding, and by the addition of 
‘“thatching’’ brood from other colonies, thus 
increasing the nurse bees of the treated colony 
out of all proportion, and consequent stimulation 
of the queen. 
A combination of both methods is frequently advis- 
able in cases where the infection has advanced beyond the 
jnitial stages, and has so far developed that the second 
generation of parasites are found in the trachea. 
It is extremely difficult to diagnose the complaint 
from symptoms, especially during the earlier stages of the 
disease, but any gradual change in the character or manner 
of the colony should be viewed with suspicion. Spring 
