THE LARCH AND SPRUCE CHERMES. 



15- 



In the autumn a larva of the Chermes pierces by means of its 

 proboscis the stem of the spruce either below a bud, or the bud 

 itself, and, thus anchored, hibernates. At this stage the insects are 

 exceedingly minute (0.5 millim.), but the proboscis is about three 

 times the length of the body, and pierces the cortex, its apex 

 reaching the neighbourhood of the cambium. Once established* 

 the insect remains in this position until her death in the following 

 June. 



In the following spring, about the middle of April, the insect 

 awakens and commences to suck, at the same time secreting, by a 

 series of glandular plates on the dorsal side of her body, a tuft of 



FIG. IV. GALLS FORMED BY Chermes ubictis, LINN. 



wool-like wax. The sucking action causes changes to take place 

 in the cells of the plant, and a gall-growth commences to make its 

 appearance. 



During these changes the larva has increased in size and 

 undergone three moults, the cast skins being found beside her in 

 the wool-like wax. 



DAMAGE TO THE HOST PLANTS. 



The injury done by these insects is considerable. In this 

 country the spruce and larch are the chief sufferers, for not only 

 do the pines appear to be less attacked, but they seem better able to 

 resist the pest. Further, the diseased trees are less able to 



