1907.] NATURAL SCIENCES OF rHILADELPHIA. 5 



now loaves that woro just hojiinniii}!; to show at the terminal buds. I 

 have been unable to see that the punctures of the stem-mothers have 

 any effect to jiroduce the galls, which seems to be caused entirely 

 by the irritation produced by the young lice inserting their beaks and 

 sucking the sap at the bases of the young growing needles. In fact, 

 only those needles enter into the formation of the gall that actually 

 have lice located at their liases. It sometimes happens that only 

 a few needles are attacked and these needles become swollen at their 

 bases, while all the others on the new growth of the twig are normal ; 

 and it is not infrequent that a few of tlie needles of the new growth fail 

 to have any lice locate in their axils, and these needles remain normal 

 in form on a gall where all others are greatly swollen. It seems pos- 

 sible, however, that the jiuncture of the stem-mother may have some 

 influop.co upon the formation of the gall, as I transferred hatching egg- 

 masses in se\'eral instances to twigs where there was no egg-mass and 

 in no case did a gall form or any of the lice live. I also transferred the 

 eggs to tender new growths of red fir (Pscudofsuga mucronata) , but none 

 of the young hatching from the eggs became established uj)on the 

 changed food plant. 



The galls (Pis. 1 and II) develop with surprising rapidity, and are due 

 to the thickening and lateral enlargement of the bases of the needles 

 together with the enlarging of the stem. In color, the growing galls 

 vary from light green to a dark purple. They are always terminal in 

 position and kill the end of the twig, except when the lice attack the 

 bases of a few needles only on one side of the new growth, leaving the 

 others, including those at the end, to develop normally, and such galls 

 are quite uncommon. 



The size of the gall depends upon the vigor of the tree and the num- 

 ber of lice that are at hand to attack the new leaves. A weak growing 

 twig cannot develop a large gall. A'igorous growing young silver 

 spruces {Picea pmryana) on the campus of the Colorado Agricultural 

 College often develop galls that are If to 2 inches in length and h to f 

 of an inch in thickness inside of the needles. Average galls have from 

 75 to 150 chambers and consequently a like number of needles, with 

 from 1 to 10 or 12 lice to a chamber. Air. Charles Jones counted 

 the needles upon three large galls for me which ran as follows: 125, 170 

 and 215, an average of 170 needles to a gall. At the base there was an 

 average of about 12, at the middle about 8 and near the tip about 5 

 young lice to a chamber. The largest number found in one cavity 

 was 32. 



Mr. George Weldon reareil and counted the lice from five large-sized 

 galls for me and they ran as follows : 463, 602, 750, 894, and 096. 



