64 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
THE GALL MITES 
FamMity ERIOPHYIDAE 
Gall mites produce galls on the twigs and leaves of plants. They 
are usually open galls with hairy surfaces, and 4-legged, elongate 
mites inhabit these cavities in great numbers. Certain bright-colored 
patches, known as “erineum,”’ on leaves, are caused by these mites. A 
related form infests the sebaceous glands and hair follicles of man. 
THE TICKS 
SuPERFAMILY IXODOIDEA 
Several species of ticks are not only annoying pests of man but 
transmit fatal diseases, such as Rocky Mountain spotted fever, tick 
paralysis, tularemia, and typhus fever. In certain localities, as the 
Bitterroot Valley and the surrounding mountains in Montana, where 
particularly fatal strains 
of the spotted fever oc- 
cur, stringent precau- 
tions must be taken by 
forest workers to avoid 
being bitten by ticks 
The life history of the 
more common ticks is 
carried through four 
stages—eggs, larvae, 
nymphs, and adults 
The larvae are six- 
legged, active creatures 
which attach themselves 
to animals and, after ob- 
taining a meal of blood, 
transform into the eight- 
legged (four pairs), or 
nymphal stage. These 
Figure 4.—The American dog tick (Dermacentor feed rat ca before trans- 
variabilis) (female). About 13 times natural forming into adults. It 
size. is this adult stage. or 
wood tick, that attaches 
itself to man and other large animals. The earlier stages usually 
feed on small animals, such as rodents. Ticks attach themselves to 
animals by working into the skin a sucking beak provided with re- 
curved barbs. A pair of jaws serve to cut a hole for the entrance of 
the beak. After the adult female tick is fully engorged, it drops off 
and lays several thousand eggs. 
Occasionally ticks become so abundant on large game animals as 
to cause anemia and finally starvation and death. The body surface 
of host animals such as deer, elk, and moose may be literally covered 
with engorging ticks. , 
The American dog tick (Dermacentor variabilis (Say) ) (fig. 4) 
is prevalent thr oughout the eastern part of the United States and, like 
its western relative (Vermacentor andersoni Stiles), commonly trans- 
mits Rocky Mountain spotted fever. Splenetic, or Texas fever, of 
cattle is transmitted by the tick Boophilus annulatus Say. Other spe- 
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