20 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



Hawthorn Leaf Miner, Profenusa canadensis (Marlatt), fig. 

 13. — Conspicuous dead areas that may include a fourth to half of 

 a leaf at the tip or side indicate damage by the leaf miner. The 

 adult is a sawfly, a beelike insect, that emerges from an over- 

 wintering pupal case in the soil and deposits eggs in the tissue of 

 unfolding leaves in May. The eggs, which may number 1 to 5 per 

 leaf, produce larvae that mine the leaves. About 2 weeks after 

 hatching, each larva makes a hole in the leaf and drops to the 

 ground, where pupation and hibernation occur. This insect pro- 

 duces one generation a year. 



Control Measure 10 (end of circular) just as soon as the 

 leaves are fully expanded. Spray applications earlier or later are 

 ineffective. 



DOGWOOD 



Dogwood Borer, Thamnosphecia scilula (Harr.). — The cat- 

 erpillar of this species is white and it has a brown head. It is the 

 larva of a clear-winged moth with a wingspread of less than an 

 inch. Eggs deposited by the female moth on the bark of dogwood 

 trees in May and June produce borers that eat through the bark. 

 These borers feed just beneath the bark, often girdling limbs 

 and small trees. The borers become full grown before winter, 

 hibernate in their tunnels, and change to pupae in the spring. 



Control Measure U (end of circular). 



Dogwood Scale, Chionaspis corni Cooley. — Usually kept un- 

 der control by natural enemies, this scale occasionally builds up 

 dense populations that give twigs and branches a whitish appear- 

 ance. The female scale is somewhat pear shaped and about one- 

 eighth inch long ; the male scale is smaller and more slender and 

 has three ridges on the upper side. Purple eggs carry the insect 

 through the winter. 



Control Measure 5 (end of circular) in late winter or Con- 

 trol Measure 3 in early summer after the eggs have hatched. 



DOUGLAS FIR 



Cooley Spruce Gall Aphid, Chermes cooleyi Gill., fig. 14. — 

 Douglas fir is the intermediate host for this small aphid, which 

 splotches the needles with cottony masses of wax that protect 

 the aphid and her eggs. Some of the aphids developing from 



