418 A^inals Entomological Society of America [Vol. IX, 



because, so far as it is possible to see, the fibro- vascular bundles 

 are not in. any way injured. It is probable that the xylem 

 functions in an infested leaf as in a normal one, supplying water 

 and raw materials. 



Our research goes to show that one effect on the pines of 

 the work of various insects is only accidental. This is the 

 piercing of the resin duct or of the cells so close to it that the 

 resin becomes infiltrated through a part of the leaf, giving it a 

 white, spotted or banded appearance. That this occurs but 

 rarely in the case of Chionaspis pinifolice Fitch is explained by 

 the common location of the insects in a single row along the 

 needles, with the beaks entering the leaf tissue at points remote 

 from the resin ducts. In the section shown in photographs 

 II and III, the saliva has dissolved tissue not more than two 

 or three rows of cells distant from the resin duct. 



II. Aspidiotiis abietis Schr. 



Another of the economically important Coccidce affecting 

 the conifers is commonly known as the black hemlock or pine 

 scale, Aspidiotiis abietis Schr. {A calif orniciis and A. florencice 

 Coleman). Observation of trees badly affected by this scale 

 shows that it does great damage at certain times. At Campo 

 Seco, Calaveras, Co., California, we* found it in 1915 the rnost 

 abundant scale of the region, stunting and killing large numbers 

 of digger pine, Pinus sabiniana. 



The appearance of Aspidiotiis abietis Schr. on the trees 

 and the damage it does is shown in photograph V. The 

 damage, a mottling of the needles followed by browning and 

 dying, is similar to that of Chionaspis pinifolice Fitch. Great 

 numbers of the leaves fall. The remaining leaves are often 

 so sickly looking, or so many are browned, that whole groves of 

 affected trees may look as if a fire had singed the leaves. One 

 noticeable difference from the work of Chionaspis pinifolice 

 Fitch is the large number of spots which have lost all chlorophyll. 

 These spots are often one-fourth of an inch in length and extend, 

 in some cases, around the needle. These spots will be discussed 

 later as "infiltrated spots." 



*Brown, Kearn B., Rpt. of Entomologist and Pathologist on Pests and Dis- 

 eases of the Campo Seco, California, Region. 1915. 



