CATALOGUE OF INSECTS. 



109 



almost hemispherical. We have only a few species ; but of these two, the 

 " cottony maple scale " and the " tulip soft scale," both attacking shade trees, 

 are troublesome. The maple scale produces eggs in spring in a prominent white 

 mass resembling cotton, and the tulip scale brings forth living young late in 

 August or early in September. The maple scale may be treated when the 

 cottony masses appear, with a mechanical mixture of kerosene and soapsuds ; 

 the tulip scale may be treated during the winter with crude petroleum, while 

 in the larval stage. 





Fig. 49. — Cottony maple scales ; a, Puhiinaria acericola on leaf ; 

 b, P. innumerabilis on the twigs. 



The DiaspiiH? contain the •' armored scales," and these differ radically from 

 the soft scales because here the scale is separable from the insect itself, which 

 lies loosely beneath it. We have a considerable number of species in our 

 State, attacking a great variety of trees and other plants, but practically only 

 three species are destructive— the San Josr or pernicious scale, the oyster- 

 shell bark-louse, and the scurfy scale. The first of these is viviparous and 

 winters in the half-grown stage, the other two are oviparous and winter in the 

 egg stage. The first has three full and a partial fourth brood during the season, 

 the others have each one brood only The differences are important, because 

 of the resulting difference in treatment. The pernicious scale may be attacked 

 during the winter with crude petroleum undiluted, and during the summer at 

 about June 15, August 1, and September 10 with a 10 % mixture of kerosene 

 and 90$ water in mechanical mixture. The others should be treated early in 

 June, while the larvse are moving or recently set, with 15$ kerosene in water. 

 The scurfy scale is thin and easily corroded ; the oyster shell louse thick and 



