THE CLOVER ROOT BORER 39 
in the contents of 12 of them, representing 8 species of birds.” The 
8 species, the number of each sex, if determined, and the number of 
root borers, if any, found in each stomach, are set forth in Table 7. 
TABLE 7.—Species and sex of birds in the stomachs of which root borers were found, 
with the number of borers in each stomach 
| 
Number of each sex 
Root borers 
Species | ; in each 
| Male | Female |Doubtful| Stomach 
| 
Streaked horned lark, Otocoris alpestris strigata Hensh----_-__- i ebb saa alll swe ee Bae 1 
Brewer blackbird, Scolecophagus cyanocephalus Wag} --------- | 3 A | ee Nee, | 0, 0, 0, 0, 1, 0, 0 
Oregon vesper sparrow, Poewcetes gramineus affinis Miller. -_- 5 153) toe A epeiea® 8 0, 0, 0, 3, 0, 0 
Townsend sparrow, Passerella iliaca unalaschcensis Gmel_._--|_-__.--- ed Pepe esene Sse ee 1,0 
Golden-crowned sparrow, Zonotrichia coronata Pall__---_____- |------~=|---~=---=- 2 0,1 
Cliff swallow, Petrochelidon lunifrons Say.--.------------------| 3 1 | 1 13, 4, 0, 9, 1 
Northern violet-green swallow, Tachycineta thalassina lepida | | 
aS ce Ea 0 Ee eS a eee Reina Se eS 2 Ie [Ese se os TRO 
‘ Pacific house wren, Troglodytes aédon parkmanii Aud. -_-______ | Dt ce che ee a A, sn | 2 
CONTROL 
The mode of life of the clover root borers, which for most of their 
comparatively long lives are confined to the interior of the host roots, 
spending but a short time above ground, renders extremely difficult 
the application of any immediately effective control measures. The 
statement of Hopkins (21, p. 31) referring to the futility and needless- 
ness of efforts at complete extermination of the bark beetles of the 
genus Dendroctonus seems applicable also to the clover root borer. 
Repressive measures tending to reduce the numbers of this insect 
pest seem to be sufficient to reduce its injury to a negligible mini- 
mum. The ability of the adult borers to migrate considerable dis- 
tances at the time of the spring flight indicates that, to be appreciably 
effective, any effort at control must be initiated on a community or 
regional basis and may involve a change jin customary farm practice. 
The one hopeful fact brought out by the investigation is that the 
species is a comparatively slow breeder, and this indicates that con- 
tinued repressive measures should have a cumulative effect and 
eventually should result in freeing a severely infested clover section 
from serious root-borer injury. [Field observations, in various regions 
differing widely in farm practice, bear out this conclusion. Data 
bearing on possible control measures have been collected from experi- 
ments performed, and from field observations on the results of dif- 
pent methods of farm practice in various parts of the Willamette 
alley. 
CONTROL EXPERIMENTS 
1. To test the effect of heat and drying on clover root borers, 
roots were dug from a field on August 22, 1916, and some of them 
placed on the surface of the ground and some lightly buried (toa 
depth of about one-half inch) in a spaded plot. Eighty per cent of 
the borers were in the pupal and prepupal stages. The temperature 
rose as high as 98° F’. in the shade. Two days later the roots were 
very dry and hard, and all stages of the borers were dead, except 
_ that one fully hardened adult escaped to the outside of a root. 
12 Skins determined by W. A. Shaw, of Washington State College, Pullman. 
