ENGLISH: ILLINOIS TREES: THEIR INSECT ENEMIES 37 



cut down during the winter to destroy overwintering grubs. 

 Healthy trees should be kept in a vigorous condition with appli- 

 cations of water and fertilizer. 



Hickory Gall Phylloxera, Phylloxera caryaecaulis Fitch. — 

 Often overlooked until the affected twigs have died and the 

 globular galls have been abandoned and have turned black, the 

 greenish insects of this species may cause considerable or little 

 injury to hickories, depending on the degree of infestation. 

 After hatching from overwintering eggs, the young aphids 

 stimulate the growth of galls on new twigs and prevent normal 

 growth or kill the twigs beyond the galls. Each gall, which is at 

 first green and may be one-half to three-fourths inch in di- 

 ameter, is crowded on the inside with the greenish plant lice. 



Control Measure 8 (end of circular) in spring about the 

 time buds unfold. 



Hickory Horned Devil or Regal Moth, Cither onia regalis 

 (F.). — The larval form of this insect is an occasional leaf eater 

 of hickory as well as several other trees. It looks enough like the 

 devil to be frightening. Approximately 5 inches long, this larg- 

 est of our native caterpillars has a green body, a red head, and 

 curving red horns just back of the head. In contrast, the adult 

 insects are beautiful olive-green moths with a wing expanse of 

 4 to 6 inches. 



Control Measure. Although a ravenous feeder, the hickory 

 horned devil does not occur in sufficient numbers to justify spray- 

 ing. Caterpillars on small trees can be collected and destroyed 

 by hand. 



JUNIPER 



Juniper Scale, Diaspis carueli Targ., fig. 28. — This pest is 

 common on various kinds of junipers, especially on plants used 

 for landscaping. The covering of the female scale is nearly cir- 

 cular and is dirty white in color. The covering of the male scale 

 is white ; it has a median ridge and is narrower and smaller than 

 that of the female. Juniper scale may develop into a dense popu- 

 lation on twigs and branches of junipers, causing them, or even 

 entire plants, to die. In May, the overwintering female deposits 

 eggs, which hatch in June. 



Control Measure 3 (end of circular) about July 1, after eggs 

 hatch. 



