3»4 
Journal of Agricultural Research 
Vol. XXI, No. 6 
adults of A. setniflavidus , emerging from H. oliviae eggs, would breed in 
eggs of H. nevadensis. 
The eggs of this closely allied species are not very numerous in the 
region infested by Hemileuca oliviae and, therefore, do not form a very 
important host for Anastatus setniflavidus. If for any reason, however, 
H. oliviae should become greatly reduced in numbers, the eggs of H, 
nevadensis would serve as a valuable host in perpetuating A. setniflavidus. 
From many indications, it is probable that such a condition of affairs 
has existed in the past. A study of the life history of H. nevadensis 
demonstrated that its life cycle and that of H. oliviae correlate very 
closely. 
An attempt was made to rear Anastatus setniflavidus from the eggs of 
Malacosoma fragilis Stretch, collected from scrub oak along the foot¬ 
hills, and to secure parasitism of these eggs in confinement, but only 
negative results were obtained. 
ECONOMIC IMPORTANCE OF THE PARASITE 
It has been very noticeable that this highly beneficial insect has been 
increasing rapidly in numbers since the spring of 1913 when the species 
was first discovered. This increase has been especially marked in areas 
of heavy Hemileuca oliviae infestation. 
In the collections of Hemileuca oliviae eggs made from different local¬ 
ities during the autumn of 1915 and the winter and spring of 1916 
the percentage of parasitism varied from 75 to only a trace. The 
species was found to be present in every locality from which H. oliviae 
eggs were collected with the exception of two isolated areas far to the 
south of the main area of infestation, in which only a very few egg 
clusters were found. 
At the present time Anastatus setniflavidus appears to be one of the 
most efficient natural enemies contributing to the control of Hemileuca 
oliviae. 
