364 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
gloves, but during an association with about ten different individuals, 
the writer never has observed an instance when complete immunity 
from the poisonous effects of the spines extended through the second 
season of work. It thus will be noted that the effect of the poisonous 
substance, contained in these urticating spines, appears to be accu¬ 
mulative rather than to cause any degree of individual immunity by 
continual contact with the poison. This characteristic is very similar 
to that occurring in the case of the Brown Tail Moth (Euproctis 
chrysorrhcea ). 
Character of Injury 
The character of the injury caused by the urticating spines of H. 
olivice may be either external or internal. 
External Injury. The most common external injury is that 
which is inflicted upon the tender portions of the tissue immediately 
surrounding the finger nails. The larvae appear to fully appreciate 
the value of the spines as a means of defense, for when grasped in the 
fingers, they immediately begin to twist their bodies convulsively with 
the apparent object of driving the spines into the flesh. When this 
result is accomplished, the wounded portion is first affected by an 
intense itching and smarting, soon followed by a white swelling. This 
swelling remains for several hours and then usually subsides, only to 
return, accompanied by the same intense itching each time this por¬ 
tion of the skin comes in contact with any object. Apparently each 
time the wounded part is touched or irritated, the poisonous agent is 
stimulated into activity. The tough skin at the ends of the fingers is 
more resistant than any other exposed part of the body, but when once 
penetrated, an exceedingly painful wound is made, although only a 
minimum amount of swelling results. It often was necessary to trans¬ 
fer men, who had suffered such injury from the effects of these spines, 
to other work until the effects of the poison subsided. 
The most painful and pronounced injury occurs when the large 
larvse come into contact with the tender skin on the back of the hand, 
on the fore-arms, ankles or other unprotected parts of the body. On 
one occasion, the writer had the misfortune to bring the back of the 
right hand directly down upon a large sixth instar larva which was 
crawling along one of the insectary benches: an intense itching and 
smarting at once began, followed by a pronounced swelling. This did 
not subside, as is ordinarily the case, and the next morning the swelling 
had extended to the wrist; the entire hand being about one-half larger 
than normal, the knuckles appearing as sunken pits, and the surface 
of the hand smooth and shiny. A sort of numbness and dull pain was 
felt throughout the member, there being, however, no sensation of 
itching or smarting. A physician was consulted who applied strong 
