46 Proceedings of Indiana Academy of Science 
and scab, and while some of our number may confess an unfamiliarity 
with either of these it is more than likely that we may have under- 
taken unwittingly to raise another variety that grows in the skin of 
the face, and is referred to as the face mite, or demodex. 
I shall not undertake to detail the steps by which the free-living 
forms, in four instances, may be traced more or less definitely to a 
parasitic condition. We may readily understand that a mite that served 
as an active scavenger might maintain the habit, and by its continu- 
ance upon an animal could readily find a supply of dead skin, hairs 
and oils, and without the necessity of any unusual power of locomotion 
could become the itch mite that burrows into the skin. Imbedded as 
it is, in the epidermis—as of human itch—it is removed from ready 
aecess to air, to a degree that respiration is practically impossible. 
Within the bodies of our poultry we find an interesting, relatively 
large mite that lives and thrives in the lungs, tracheae and the air- 
sacks of the bird. Their life is rather unusual in that they are able 
to migrate about the tissues of the host, or even out of the mouth 
without apparent inconvenience. They are taken in with the food 
of the bird. The parasites feed upon the tissues of the host and give 
birth to living young, thus reducing to a minimum the hazards to 
which many of the other forms are subject. 
Experiments to determine the power of mites to carry on respira- 
tion yield rather negative results, and it is held that many of these 
which imbed themselves in the body of the host are able to secure suffi- 
cient oxygen from the tissues to maintain their bodily activities. In 
an attempt to determine whether the total exclusion of air would have 
an effect upon the organism I mixed in vaseline several hundred of che 
feather-eating analgesid mites that were secured from a dead ostrich, 
and compared their activities with control specimens that had migrated 
from the body of the host to form a dense mass about the ocular of a 
microscope and the neck and shoulder of a bottle that stood upon the 
laboratory tables upon which the dissection of their host had occurred. 
At the close of the tenth day about half of the number were still 
struggling in an effort to creep out of the vaseline and in the course 
of the next two days the movements ceased completely. The last of 
the individuals that were not imbedded in vaseline died within fourteen 
days after their migration from the host. It would appear that the 
earlier death of the last individuals, by so much as two days, was due 
more to the exhaustion of the parasites in an effort to escape from the 
vaseline than to the complete exclusion of air. Therefore, if species of 
external mites which live normally in the air are so little affected by 
complete exclusion of air the effect must be less marked upon those 
which burrow deeply into the tissues and out of reach of free air. The 
tracheal respiratory organs are reduced or missing, among mites. 
The face mites, demodecidae, seem quite thoroughly adapted to 
live imbedded in the oily secretions in and about the minute hairs of 
the face of several mammals, and even of man. Here they feed upon 
the sebaceous secretion, and I have observed instances in which they 
seem to have chewed the hair bulbs with their mandibulate jaws. To 
suggest that a person might unintentionally harbor parasites, whatever 
