212 DISEASES OF DOMESTICATED BIRDS 
of content of metallic mercury. The mercurial ointment is mixed 
with one or two parts of vaseline. One ounce is sufficient to treat 
about seventy-five hens. In the case of chickens it is desirable to 
place a piece of ointment the size of a pea, under the wings or around 
the vent. In older stock the best place is on the skin just beneath 
the vent. The treatment seems to remain effective for some time, 
so that lice hatching after the application are also killed. It is not 
clear that the use of mercurial ointment is cheaper or more effective 
than sodium fluorid. Bishopp and Wood find that when used as 
recommended, the mercurial product has little effect upon head and 
wing lice. Used in larger amount it is more expensive and injurious. 
The dust bath constitutes the natural defense of fowls against lice 
and should be considered in connection with the measures against 
them. It is desirable that the box be located in the sunlight, and if 
covered, will prevent widespread dissemination of dust in the poultry 
house. The finer and lighter the material available, the better. 
Fine siftings from coal ashes is a desirable addition to the dust, as 
also are snuff, sulphur and dry slaked lime. The dust bath, while 
desirable, cannot be depended upon to the exclusion of more aggres- 
sive measures. It has only a temporary effect upon the numbers 
of lice on the fowls. Some birds seldom or never use the dust box. 
In a flock infested with lice special care must be taken to free the 
sitting hen from these parasites and to protect young chicks in like 
manner. 
THE BIRD FLEA 
The common bird flea, Pulex avium, attacks a large number of 
species of birds including fowls and pigeons. The parasite is pro- 
vided with piercing mouth parts with which it penetrates the skin and 
extracts blood. The irritation produced by the fleas causes pruritis 
and loss of rest. 
Life history. The eggs are laid in hens’ nests or on manure on 
the floor of the poultry house. 
These nits after a week or ten days 
hatch into white larvee which are 
nearly a quarter of an inch in 
length. The larval stage lasts from 
ten days to three weeks, depend- 
ing upon the temperature. The fully developed larva becomes 
secreted in some crevice and spins itself a cocoon. In this structure 
the larva develops into the adult stage during a period varying from 
Fie. 43. Larva of hen flea, enlarged 
20 times. (Railliet) 
