THE TROPICAL HORSE TICK. 197 
Adults of this tick have been collected on animals in Texas at all 
times of the year. However, they appear to be most abundant 
in the spring and early summer. Nymphs have been collected 
on animals in considerable numbers in February, March, and April, 
and in one instance in August. With little doubt the immature 
stages are to be found on hosts nearly all the year round. 
ECONOMIC IMPORTANCE. 
Aside from the fact that this species occasionally attaches to 
man and domestic animals and often causes considerable annoy- 
ance, it is of no economic importance. The ticks are easily removed 
from a host and their attachment has not been known to produce 
any serious consequences. 
NATURAL CONTROL. 
The many bird and other enemies of the cattle tick undoubtedly 
prey upon this tick also. Dogs have been observed by us to crush 
them with the teeth, both when attaching and after dropping. 
ARTIFICIAL CONTROL. 
This species has not been found to occur in numbers except upon 
the dog and some wild mammals. When dogs become badly infested 
_the ticks may be removed by washing the dogs with one of the 
standard tick dips. Ordinarily hand picking will suffice to keep them 
in check. 
THE TROPICAL HORSE TICK. 
Dermacentor nitens Neumann. 
The common name of this species is derived from the fact that 
its distribution is restricted almost entirely to the Tropical Life Zone 
and that the horse is its principal host. 
DESCRIPTIVE. 
Adult (Pl. XIII, figs. 8-10, 13, 14).—Males 2.5 by 2 mm. to 3 by 
2mm. Females, unengorged, 3.25 by 1.75 mm. to 3.5 by 2 mm.; 
engorged, 9 by 7 mm. to 12 by 9 by 5mm. _ Both sexes are reddish 
brown and without white markings. 
Nymph (Pl. XIII, figs. 7, 11, 12).—Unengorged, about 1.33 by 
0.9mm.; engorged, 2.9 by 1.8 by 1mm. to 3.5 by 2.2 by 1.3mm. Color, 
unengorged, pale brownish yellow; engorged, dark gray. Capitu- 
lum, 0.359 mm. long (from tip of hypostome to base of emargination 
of scutum); scutum 0.54 mm. long by 0.641 mm. wide. The shape 
of the nymph, particularly when engorged, as with the engorged 
female, is quite typical of the species; the greatest width is at the 
