THE SPECIFIC EFFECTS OF CERTAIN LEAF-FEEDING 

 COCCIDAE AND APHIDIDAE UPON THE PINES. 



By Kearn B. Brown, Stanford University. 



In the great volume of entomological literature, we find 

 but few references dealing with the specific effects of the attacks 

 of sucking insects upon the tissues of their hosts. Statements 

 describing the appearance of the work to the naked eye are, 

 at most, meager in detail; and there are few records of morpho- 

 logical and chemical study of the affected plant tissue and of 

 histological study of the parts of the insects concerned. The 

 present paper summarizes the results of a year's work in the 

 Entomological and Botanical laboratories of Stanford Uni- 

 versity on a few species of plant-sap sucking insects living on 

 the needles of the pines and the precise character of the results 

 of their work. 



Over a year ago we became interested in finding the cause 

 of certain, peculiar, light spots on the needles of the various, 

 species of pine found in California, the presence of which has 

 not heretofore been explained. Also, it was noticed that light, 

 greenish-white areas frequently surround scales of Chionaspis 

 pinifolicB Fitch, the white pine scale, and of Aspidiotus ahietis 

 Schr. {A. californicus and A. florencice Coleman), giving the 

 leaves of a badly infested tree a mottled, sickly appearance. 

 Later, these spots were observed to turn brown, often killing 

 large numbers of the needles. The purpose of this investigation 

 was to find an explanation for these phenomena. 



The study of the insects in situ is of primary importance in 

 working out this problem. Two methods suggest themselves: 

 (1) observation of the insect at work and of the wounds made 

 on the plant. The latter should be observed immediately 

 after the insect has stopped feeding and at intervals later to 

 determine the ultimate effect of the sucking upon the metabolism 

 of the plant. Another method, (2), is morphological study of 

 the insect and its work by means of sections through the 

 affected tissues and the beak of the insect. Both of these 

 methods have been used in the investigation here summarized. 



