1922 ] Johnson — Notes on Distribution and, Habits of Bird-Flies 79 
NOTES ON DISTRIBUTION AND HABITS OF SOME OF 
THE BIRD-FLIES, HIPPOBOSCIDdE. 
By Charles W. Johnson, 
Boston Society of Natural History. 
The following notes on this interesting group of flies have 
been brought together in the hope of thereby encouraging orni- 
thologists to observe more closely the occurence of these insects 
on the various species of birds. While the wide distribution and 
great diversity of hosts frequented by one species seems some- 
what at variance with the distribution of other insects as well as 
their hosts, it is impossible with the limited material and data at 
hand to arrive at any other conclusion regarding the species. 
Highly specialized forms always lose many of the distinguishing 
specific characters present in the species of the higher groups less 
restricted in their habits. Living as these flies do under similar 
and uniform conditions, notwithstanding their wide distribu- 
tion, they would naturally show but little variation. 
The occurence of the same species of fly upon non-migrating 
birds confined both to the tropical and boreal regions would in- 
dicate that they are naturally transmitted from one to the other 
by the migratory species; and the interesting example of phoresy 
recorded below shows how the various species of the wingless 
Mallophaga are also distributed. 
One of the peculiar habits of these flies, and one which 
probably accounts for so few of them being taken by ornithol- 
ogists, is that they are rarely seen while the bird is warm, but as 
the dead bird becomes cold they dart from it as if terror-stricken 
at losing their host, for if another cannot be found soon, it pro- 
bably means death. If in this quick flight they happen to alight 
on one’s clothes, there is a possibility of capturing them, if 
caught firmly between the thumb and finger, for their smooth, 
flattened bodies slip easily through one’s fingers and when once 
they escape they are rarely seen again, as they dart into any little 
crevice that offers protection. 
Their method of reproduction admits of no great increase, 
producing but one large egg at a time, which develops into a 
