140 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
the sub-family Leiothinae ; species uncertain. This parasite is represented in Fig. 10. 
The louse lives amongst the feathers of the birds, and is generally found on the under- 
surface of the long feathers of the wing on' either side of the quill. When disturbed 
the parasite moves rapidly among the feathers and, because of this, together with its 
small size and flat body, it is difficult to capture. Eggs are laid and glued to the 
under surface of the feathers. On the death of the swift, by placing the body in 
water in a white dish, the lice come to the surface of the feathers, and can be picked 
off by means of a dissecting needle. The lice feed on the feathers of the birds and 
also on small quantities of blood and lymph drawn from their hosts ; blood and bits 
of feathers can be found in the stomach of both male and female lice on dissection. 
It was in the bodies of these lice that a further development of the embryo of 
F. cypseli was observed, and it was fortunate that specimens of the young filaria were 
obtained in all stages of their metamorphosis up to those in which they bear a marked 
resemblance to their parents. 
If we consider for a moment the habits of the swifts, as described above, it is 
easy to understand how lice, infected with the parasite, can travel from one bird to 
another through the medium of the feathers, and so spread infection. Though I 
have examined the nests of the birds most carefully I have never found lice in the 
dried mud and grass. 
Infection among the Gambian Swifts. — The members of the Expedition to Nigeria 
have shown that the habitat of the embryo of F. cypseli is essentially the lymph, they 
rarely found embryos in the peripheral blood, and never in the heart's blood of the 
infected birds. It was pointed out that the claws of many of the birds infected were 
generally found to be swollen, and on careful manipulation, serous fluid, free from 
blood, could be obtained from these claws, and in the fluid many embryos were usually 
seen. 1 These facts were fully confirmed at Bathurst. 
The method of examining the birds was as follows : the side of one of the 
claws was pricked once or twice with a fine needle, and then slightly compressed ; 
from the drop of blood-stained serum exuded a coverslip preparation and a film were 
made. In infected birds clear serum would generally exude from the punctures with- 
out pressure of the claw. 
On November i, eight adult swifts were examined ; three were found to be 
infected. On December 2, six swifts were examined, two were infected. Two young 
birds, just fledged, examined, were not found to be infected. On December 23, two 
adult birds were examined with negative results. These birds were taken from two 
houses in the centre of the town. After the 23rd of December I was never able to 
obtain birds for examination ; the dry season was fully advanced ; there was a great 
scarcity of insects of all sorts ; and for these reasons I judged the swifts had left the 
locality. 
1. Report of the Malaria Expedition to Nigeria (1900), Part II, Fi/ariasis, Liverpool School of Tropical Medicine. 
