THE IMPORTED PINE SAWFLY. 17 
within eight days; and from 40 adults supplied with cotton soaked in 
sugar water all the males died within three days, but all the females, 
except 1, were living on the thirteenth day, and all were not dead 
until the seventeenth. 
Table 9. — Cocoons of Diprion simile collected during the winter of 1916-17 and examined 
for parasites. 
Condition. 
Number. 
Per cent. 
1,321 
1,210 
191 
518 
41 
37 
6 
Dead r 
16 
Total 
3, 240 
100 
Several experiments were made with D. nigrocyaneus Xorton, with 
the object of observing oviposition and studying the relation of the 
parasite to this host. All resulted in failure, however, for no parasi- 
tism was obtained, although the chalcids endeavored to oviposit, 
usually more than once, in the cocoons supplied. Possibly D. 
nigrocyaneus does not attack Diprion simile in the cocoon stage. 
The presence and activity of these parasites must not lead to the 
conclusion that they will bring about an effective natural control of 
D. simile. If the permanent establishment of this pest is to be pre- 
vented, or if its multiplication and work are to be checked, artificial 
control measures, such as those recommended, must be applied. 
HOSTS. 
If the imported pine sawny is able to feed on a number of species 
of pine this will be an important factor in the establishment of the 
species in this country, and it is extremely desirable to know if it 
can and will use our native pines successfully. Restricted to intro- 
duced ornamental species of pines, Diprion simile would at worst only 
become a nursery and estate problem, but if it will attack our Ameri- 
can pines it may become a serious forest problem. At present the 
sawny seems to be confined to young pines of imported species and has 
only been recorded from nurseries and estates. 
To determine the range of host plants which this insect can success- 
fully utilize, two series of host-tree experiments were conducted. One 
was to determine the ability of Diprion simile to use a given host suc- 
cessfully from oviposition to the production of adults. The other was 
to determine the preferred host plants of the sawny, if there are any. 
In the first series of experiments a number of adult males and females 
of D. simile were confined upon a particular species of young pine to 
observe its suitability. In the experiments on choice of host species a 
quantity of small native and introduced pines' were transplanted into 
the large screen-wire insectary previously mentioned and a number of 
males and females liberated within the inclosure. 
Table 10 gives the results of the experiment to determine the im- 
ported pine sawny 's choice of host plants. Fifty-four male adults and 
fifty-nine female adults of D. simile were liberated in the insectary, 
