37 
The Ninebark Borer 
{Scsia scitiila Harris) 
Dogwood and ninebark shrubs {Ccriius sp. and Opulaster opuli- 
foliiis) in the Chicago parks are generally infested, and often seri- 
ously injured, by a boring oi girdling caterpillar (Fig. 39) which 
works just beneath the bark, mainly at the junction of the branches 
Fig. 39. Ninebark Borer, Sesia scitula larva. 
About 3 times natural size. 
or in the neighborhood of an old dormant bud. The burrows of the 
borer sometimes extend lengthwise of the branch, and sometimes 
girdle it near its origin. In 1908 nearly every shrub of the ninebark 
in Washington Park was infested, and many of the branches were 
killed by this larva. The species also infests the chestnut, and has 
been bred from galls on twigs of the oak. 
The creamy white larva, half an inch long in September, passes 
the winter in its burrows, and emerges, according to our observa- 
tions, in late June or in July. The head is brown, darkening almost 
to black towards the mandibles. The prothorax is slightly brownish, 
with two oblique brown markings on its posterior half. The re- 
Fig. 40. Ninebark Borer, Sesia scitula, adult female. 
About 3 times natural size. 
maining segments are creamy white, except the last, which is pale 
reddish-brown. 
The winged insect (Fig. 40) is deep blue-black on the thorax 
and abdomen, the former with a yellow line and a yellow patch on 
each side, and the latter with a yellow line at its base and, in the 
