LIE SaISTORY OF AN OAK MWIG GiIRDLER* 
Agrilus arcuatus Say and var. torquatus Lec. 
By A. G. RUGGLES 
In August, 1914, my attention was called to the blighting of the 
oak leaves on the University Farm Campus. The leaves attached 
to the tips of the twigs wilted and died as if struck by a blight. Upon 
investigation it was found that the damage was localized, being con- 
fined to a comparatively small area around the Twin Cities (St. Paul 
and Minneapolis) and extending to Stillwater on the St. Croix River. 
In studying the damage closely a small buprestid larvae, evidently 
belonging to the genus Agrilus, was found burrowing beneath the bark 
at the tip of the twigs, causing the death of the part beyond the bur- 
row. In looking up the literature it was found that in California 
Agrilus politus Say? performed a similar operation on a species of oak 
there. No other reference was found to any other insect behaving in 
this manner, and hence in our notes we referred to the species as 
Agrilus politus. It was not until June, 1916, that adults were obtained 
and identified by Dr. Schwartz of the U. S. Bureau of Entomology as 
Agrilus arcuatus Say and variety torquaius Lec. 
The life history of the insect has been followed very closely for 
four years, notes being taken at short intervals for the first two years 
and at longer periods for the last two years. Beyond a doubt it is the 
worst pest of black oaks discovered in recent years. R. N. Chapman 
in the Journal of Agricultural Research, Vol. III, No. 4, Jan. 15, 1915, 
published, ““SSome Observations on the Life History of Agrilus biline- 
atus Web.” A, bilineatus and A. arcuatus work in the same species of 
oak—but particularly Quercus rubra L. The former attacks the trunk 
and larger limbs while the latter attacks the tips of the branches and 
works downward, often cutting off branches eight feet long. These 
two Agrilus species threaten the extermination of the black oak group 
in the part of Minnesota above indicated, A. bilineatus attacking from 
below and working upward and A. arcuatus attacking at the end of the 
twigs and working downward. 
1 Published, with the approval of the Director, as Paper No. 169 of the Journal 
Series of the Minnesota Agricultural Experiment Station. 
2,Cal. Hort. Com. Mo. Bul. Vol III, No. 3, p. 150. 
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