August, ’18] CAFFREY: HEMILEUCA URTICATING SPINES 367 
the species exists, as has been found necessary under similar conditions 
in Brown Tail Moth investigations. 
Effects of Urticating Spines on Animals 
It was often noticed that small areas of good grazing grass in infested 
pastures were left untouched by the animals. An examination of 
these untouched areas generally showed that the grass was infested 
by the urticating spines shed by the larvae in the process of moulting. 
This was evidenced by the fact that upon running the fingers through 
this grass, the characteristic itching and smarting was experienced. 
From the facts previously given, the ill effects of these spines on the 
tender mouth of any animal grazing upon infested grass of this char¬ 
acter, can readily be imagined, and it is not strange that the range 
animals soon learn to avoid all grasses in the vicinity of H. olivioe 
larvae. This fact is an important item in the total loss occasioned by 
the pest. 
Urticating Spines of Closely Allied Species 
Larvae of the two closely allied species, Hemileuca nevadensis Stretch 
and Hemileuca sp. (maia variety ?) Busck, both of which occur in this 
region, were observed to have the same poisonous properties as have 
been noted under H. olivioe. The larvae of H. nevadensis feed upon 
willow along the banks of the Red River in northeastern New Mexico 
and the larvae of Hemileuca sp. {maia variety ?) feed upon scrub-oak 
along the mesas and foothills of the same region. 
Conclusion 
From the foregoing, it will be noted that the urticating spines of 
H. olivioe are a source of danger and discomfort to people coming in 
contact with the species. The effect of the poisonous agent in these 
spines appears to be accumulative in its nature rather than to confer 
any degree of immunity through continual contact. 
The injury may be internal or external. The external injury varies 
in severity according to the part of the body affected, and may lead 
to partial disability for short periods. The internal injury is more 
severe than the external injury, and in advanced cases, may result in 
typical asthmatic symptoms or other disorders of the respiratory 
tract. 
The urticating spines from the moulted skins of the larvae become 
scattered through the range grasses and render small areas unfit for 
grazing. 
