34 Tite Green Spruce Aphis 



difference in the appearances produced, i.e. complete and rapid defolia- 

 tion in the Sitka, browning and slow defoliation in excelsa and still less 

 defoliation in pungens and scarcely any in the glaucous variety kos- 

 teriana. 



Life-hislory. 



So far I have been unable to find any sexuparae and I have searched 

 carefully for four years. 



I have found apterae from early January on to December. The first 

 alatae occurred on the 20th of March at Woking, but in small numbers. 

 At Wye I have never noticed any until June and in July many occurred 

 and went on appearing in numbers into August. After August the trees 

 kept under observation showed comparatively few aphis until the 

 end of September, when they again became fairly common and some 

 could always be found right into December. These winter apterae 

 seldom producing any living young. At this time both mature and 

 immature apterous viviparous females occur. 



Gillanders says that it may be found in winter. Mr McRae writes 

 me that where infestation is serious the aphis appears to live on the trees 

 throughout the winter, and Mr Black also noticed that this aphis persists 

 throughout the year. I have vainly searched for sexuparae this year, 

 a year when the sexual brood of aphides has been particularly noticeable. 



The apterous aphides usually occur along the needles, a single one 

 settling on each needle and giving rise to a colony of young, which later 

 spread out and do the same ; where the apterous mother feeds a yellow 

 spot occurs, sometimes with a reddish tinge and which later darkens ; 

 two oi' three of these spots on old trees seem sufficient to kill the needle, 

 whilst in young ones they remain, the needles but seldom completely 

 dying. The aphides also wander about on the shoots and remain and 

 feed there. 



They do not seem to attack the new growth to any extent in summer, 

 but in autumn and winter a few may be found on the young growths. 



In October and November I counted about six apterae to every 

 foot of branch examined and a few small young with them. The insect 

 is very sluggish both when in the apterous and alate stages, but if a 

 branch is cut off they become active in a few hours and wander away 

 from the needles. 



It thus appears that this insect lives normally through the winter 

 as apterae and that sexuparae must be very rare and are so far un- 

 known. 



