284 OHIO EXPERIMENT STATION: BULLETIN 332 



hand lens. In the first place it is larger than most others, the 

 mature female scale measuring one-eighth of an inch in diameter. 

 Moreover, the young scales have a characteristic habit of clustering 

 about the mother in very regular formation as indicated by the 

 accompanying illustration, Plate XLVII, Fig. 3. Very frequently 

 one finds the mother scale surrounded by a perfect circle of young. 

 Finally, when the scale is removed and the body of the mature 

 female is exposed, there will be seen a deep notch on each side of 

 the anterior, rounded portion, thus abruptly setting it apart from 

 others of this group. 



The general body color of the mature female scale is gray and 

 the reddish-orange exuvium is slightly to one side. The male scale 

 is smaller and elongated. 



Life history and habits. — The winter is passed in the adult 

 stage, the female laying her eggs in early spring. Hatching occurs 

 soon and by June this brood has matured and the eggs for another 

 brood have been deposited. There are two and perhaps more gen- 

 erations annually. 



Nature of work. — Twigs and the smoother bark on limbs and 

 trunk are affected by this species, sometimes with such severity 

 as to encrust the bark. The English walnut scale is much worse in 

 cities than in the country, sometimes actually killing trees, but more 

 frequently merely giving them a sickly, unhealthy appearance. 



Food plants. — Linden, horse-chestnut and buckeye are the most 

 severely infested of the common Ohio trees, but the list of hosts 

 embraces ash, maple, apple, box-elder, elm, cottonwood, currant, 

 cherry, locust, peach, pear, plum, English walnut, prune, sWeet gum 

 and apricot. 



Distribution. — This insect occurs in most paVts of Ohio and is 

 widely distributed over the United States. 



Natural enemies. — The following Hymenopterous parasites are 

 reported by Essig (41) as having been reared from this scale: 

 Aphelinus diaspidis How., Encyrtus ensifer, Prospaltella aurantii 

 How. and Signiphora occidentalis How. 



Control. — The standard sulphur sprays and miscible oils applied 

 in the usual dormant strengths have proved satisfactory control 

 measures for this species in experimental work in Ohio. 



THE OBSCURE SCALE 



{Chrysoiiiphalus obscurus Comst.) 



Description. — As the name signifies, the obscure scale is rather 

 difficult to detect, particularly when it occurs on oaks and other 



