1916] Coccid(B and Aphididce on Pines 419 



Morphological study of infested needles shows that the 

 manner of sucking is similar to that described above for 

 Chionaspis pinifoUce Fitch. Photograph VI of the setae in situ 

 in a needle of Pinus sahiniana gives an idea of the first stage 

 of the work. Owing to the size of the scale and the shape 

 of the needles of many of the hosts, this scale frequently pierces 

 the resin ducts accidentally. Credit for this discovery is due 

 to Mr. E. A. Cornwall, graduate student in Entomology at 

 Stanford University, who, in preliminary work in this investiga- 

 tion, cut sections showing this. The ''infiltrated spots," 

 caused by this tapping of the resin duct, are similar to those 

 due to aphid attacks and shown in photograph VIII. A 

 section of digger pine needle, showing killed cells infiltrated 

 from broken resin duct is shown in photomicrograph VII. 



III. AphididcE on Pines. 

 Several species of Aphididce, or plant lice, infest the pines, 

 including, at Stanford University, Lachnus pini-radiatcB David- 

 son and Essigella calif or nica Essig. As but little is known of 

 the effects of conifer-feeding Aphididce, we have made careful, 

 daily observations of these species for a period extending over 

 six weeks. We aimed to find out their habits and to determine, 

 if possible, whether there is any relation between the aphid 

 attacks and three abnormal conditions found on infested 

 needles. Examples are shown in Photograph VIII. They may 

 be described as: 



(1) minute white spots; 



(2) gumming, apparently from small leaf punctures; 



(3) infiltrated spots similar to those described above on 

 page 418. Some of the infiltrated spots show a reddish area 

 in the center of one side, either as a small red mark or as large 

 spots of dead tissue. 



Lachnus was found to be a comparatively sedentary species. 

 It seldom removes the beak from the tissues, often remaining 

 in one position for weeks at a time, even in stormy, windy 

 weather. It is conspicuous, usually being found in colonies 

 of two to six apterous females, the progeny of one stem-mother, 

 on one side of the needle. The whole colony is not over an 

 inch in length. The part of the leaf where they are working 

 is covered with gray, waxy secretion. The leaves finally 



