48 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



OAK 



Borers. — Like other trees when weakened by transplanting 

 shock, dry weather, or poor environment, oaks may be attacked 

 by several species of borers. The flatheaded apple tree borer 

 (see under Maple) and the carpenterworm (see under Poplar) 

 are common pests of oaks. 



Control Measure U (end of circular) . 



Periodical Cicada, Magicicada septendecim (L.), fig. 35. — 

 The female of the periodical cicada, which seems to prefer the 

 terminal twigs of oaks for laying eggs, causes damage by tearing 

 the bark and wood where she thrusts eggs into a twig. The dam- 

 age resulting from many egg deposits in a twig causes it to die, 

 and possibly to break off. Tiny nymphs hatch from the eggs, 

 drop to the ground, burrow into the soil, and subsist for a 13- or 

 17-year period on the plant juices they can obtain from roots. 

 The nymphs emerge from the ground in early summer, attach 

 themselves to nearby objects, and molt to become adults. Both 

 male and female are black and robust; they have reddish eyes, 

 legs, and wing veins. With strident song, the males announce the 

 presence of cicadas in great swarms at intervals of 13 or 17 

 years. 



Control Measure 19 (end of circular). 



May Beetles, Phyllophaga spp. — The adults of many species 

 of Phyllophaga (May beetles or June bugs) feed on the foliage 

 of oaks and other trees, sometimes in such numbers that they 

 defoliate small trees. These adults, which feed at night, are at- 

 tracted to lights. Most of the beetles are solid brown in color and 

 are one-half to three-fourths inch long. Eggs deposited by the 

 female in the soil produce larvae, white grubs, that feed on the 

 roots of grasses and other plants. Most May beetles have a 

 3-year life cycle. 



Control Measure 1 or 2 (end of circular) when beetles are 

 feeding. 



Twig Pruner, Elaphidion villosum (F.). — Although not a 

 major pest, the larva of this species when present in considerable 

 numbers may litter a yard in late summer with twigs from oaks, 

 elms, hickories, maples, and other trees. A clever animal, the 

 larva tunnels around a twig under the bark, cutting into the twig 

 to such an extent that it is easily broken off in the wind. Having 

 burrowed farther toward the tip of the twig, the pruner falls with 



