1907.] 



A Cause of Larch Canker. 



553 



fresh places, A larch canker, for example, may arise solely 

 without the intervention of any such insects, and the wind 

 would assist in the spread of the spores, but the chances would 

 probably be against a very great distribution of the contagion 

 in this manner. On the other hand, if the wound should be 



FIG. 3. — Fungus fairy fiy (Caealzus flavidus) (much magnified). 



visited by these insects they would in endeavouring to find 

 other fungus-smitten areas, assuredly carry the spores to trees 

 hitherto healthy, and as a result fresh cankers might arise. 

 At any rate it is hardly possible to examine either a " broom " 

 or a canker without finding numbers of these little insects. 



fig. 4. — Head of Caecilius flavidus. Front view with jaws distended. 



It has been my practice immediately upon the receipt of a 

 canker to place it in a jar to which no other insects could obtain 

 access. After keeping a specimen for several weeks groups of 

 I these creatures appear, so that it is evident that the eggs must 

 have lain concealed within the crevices. 



