1916] Coccidce and Aphididce on Pines 415 



It has been necessary to develop or adapt several points in 

 microtechnique in order to use the second of these two methods, 

 i. e., morphological study. These points have been discussed 

 in an article* which recently appeared in Science. 



I. The White Pine Scale, Chionaspis pinifolice Fitch. 



The white pine scale, Chionaspis pinifolice Fitch, is a con- 

 spicuous and widespread pest of pines in North America. 

 It is, as a rule, particularly common on transplanted trees. 

 In the East, the most important host is the white pi^ie, Pinus 

 strobus, which it has attacked wherever this pine is grown in 

 North America, often proving a serious pest. It has done 

 great damage to the Monterey pine, Pinus radiata, in California. 



The white pine scale is entirely a leaf feeder. The flat side 

 of the needles is usually occupied, but in a serious infection the 

 rounded surface is covered as well. As a rule, a single row will 

 be found along a needle, the scales occuring in groups. 



As seen in Photograph I, wherever a scale or group of scales 

 occurs, a light colored area with much less chlorophyll than 

 usual is found. It is evident that this is due, primarily, to the 

 sucking of the insects. After many months of sucking, many 

 of the light-colored areas die and dark, reddish spots appear. 

 One of these spots is shown on the upper needle in Photograph I, 

 directly under the scale. Later the needles change from the" 

 mottled appearance they have had for some time to a uniform, 

 sickly, yellow color and finally die. Great numbers of the 

 scales are attacked by parasites, but these usually come too 

 late to be of service in checking the damage done by the par- 

 ticular insects they parasitize. It is evident that they partially 

 overcome the enormous increase of which this insect is capable. 

 Lady bird beetles, including Chilocorus bivulneriis Muls., the 

 two-stabbed lady bird, are usually of great help. 



The amount of damage which a pest does is in direct pro- 

 portion to its numbers. An insect may be widespread, but it 

 may be held in check so that it is usually of comparatively 

 small importance. Occasionally this species becomes abundant 

 enough to cause great damage. We find that when for any 

 cause the trees are at all weakened, for instance by fire or lack of 



*Brown, Kearn B., Microtechnical Methods for studying certain plant- sucking 

 insects in situ. Science, N. S. Vol. XLIV, p. 758, 1916. 



