546 Journal of Agricultural Research voi. xxxi, no. # 
The volunteers in a hay or grain field often are quite sufficient in 
numbers, therefore, to attract dispersing beetles, but they are not 
always the most important source of infestation. In grain fields 
where cultivation has broken up the soil, volunteers get an early 
start and offer hospitality to adults emerging from estivation in the 
same field that had been in potatoes during the preceding year. 
In timothy, however, the volunteer makes slow growth and is 
infested only late in the season. On the large plants in the grain 
fields the insect can pass its entire seasonal cycle without resort to 
the cultivated plants. The volunteers, therefore, constitute a local 
reservoir from which adult beetles emerging from pupation or esti¬ 
vation disperse to adjacent wild plants or cultivated fields. The 
writer is of the opinion that the insect may come from such a source 
as this when it suddenly appears in well-sprayed fields, as it often 
does. Occasionally the beetles migrate from defoliated volunteers 
in great numbers. In one case noted on August 13,1921, a field of 
seedling potato plants became so heavily infested with adults from 
nearby volunteers that it was necessary to hand pick the field in 
order to save the small plants. One plant harbored 151 adults. 
The source of this infestation was an adjacent oat field in which the 
volunteers were very numerous and well developed. 
In another example, rye and buckwheat were sown following 
potatoes, and Irish Cobblers were planted in sod immediately adjoin¬ 
ing. The volunteers showed a 78 per cent infestation by the first 
brood as compared to 11 per cent in the cultivated field. Obviously 
the emerging adults were satisfied with the volunteers alongside of 
which they emerged from winter estivation as compared with the 
Fig; 1.— Left: “Volunteer" potato plants in buckwheat and rye. Right: Irish Cobbler field 
