Life Among Parasitic Animals A5 
fowl four are commonly found on the reputed wild ancestor, the jungle 
fowl. 
According to Kellog’s well-sustained thesis we are led to the con- 
clusion that the progeny of the present-day species of lice are the direct 
lineal descendants of the lice which began as parasites upon the an- 
cestors of these birds and, in so far as identical species appear upon 
closely related birds, it implies an alteration of the bird without that 
of the parasite, while in other instances, on identical species of birds 
of wide geographical range, mallophaga have been found that exhibit 
either varietal or even specific differences. It follows, then, that phy- 
letic relationship may be determined in some cases of doubtful rela- 
tionship of host, by a close study of its wingless, permanent ectopara- 
sites. In this connection it is of interest to recall that certain anthro- 
poid apes harbor two of the three species of pediculid lice which are 
common to man, and that one of the anthropoids bears another species 
of the same genus of pediculoid louse, but which does not occur on man. 
The blood-sucking lice, or Anoplura, to which the pediculid lice 
belong, seem to be derivable from the mallophaga from which they 
differ structurally and chiefly in a modification of the mandibles into 
piercing organs which serve to perforate the skin of the host and vo 
make the blood available for food. The same general sensitiveness to 
host relationship exists as was expressed of the mallophaga. The chem- 
ical composition, as shown by the blood serum reactions, which indi- 
cate a specificity of blood, seems to be one reason why the four. hun- 
dred known species are as widely distributed on the mammals and that 
none have been taken from birds. It aids us to understand why man 
and the anthropoids may have closely related forms. 
Migration from parent to young and from host to host occurs as 
was stated of the mallophaga, and with some of the same limitations. 
Here, however, the individuals maintain their relation upon the host 
more by the form and size of their claws than by grasping mandibular 
structures such as occur among the mallophaga. 
The frantic efforts of a vigorous host would serve to dislodge indi- 
viduals less well prepared to grasp the hairs. One may well conceive 
that the struggle for life, the free-for-all, in the louse world was one 
like that in which the stronger Spartans were produced by destruction 
of the weaklings, and that after an extended period of such elimina- 
tion a race was bred that could maintain a foothold with clasping claws 
that fit a hair with the nicety of a caliper. A careful examination of 
these clasping organs shows that they can be used upon a hair of 
almost definite diameter and even of a definite shape. A hair much 
larger than those of the accustomed host frequently would be too large 
even to permit the presentation of the claspers, while a hair much 
smaller could not be held tightly at all. 
The next large group of ectoparasites which is known principally 
in the free state, but which has a large number of members that have 
undertaken to live upon other animals, as well as upon plants, are 
known as mites. Instead of feeding on dry plant products and dead 
animal products, or upon the body fluids they have undertaken to go 
more deeply into the body. We know them as the itch mites, mange 
