14 



rounded anteriority, pointed behind and about the size of a grain of 

 flaxseed. In young birch trees, the bark of which does not readily 

 separate in layers, the insect infests knots, accidental wounds, or the 

 vicinity of buds. In this case its form is not flattened but well-rounded 

 and pyriforin, and it occupies a deep pit sunk vertically into the cam- 

 bium and even into the young wood. Occasionally in white birch, and 

 also in aspen, similar pits are formed, whenever an accidental wound 

 allows the insect to gain access to the succulent inner bark, in which 

 alone, by some obscure absorptive process, the formation of such a pit 

 is possible. 



a a 



Fig. 1.— Xylococcus betulce: a, branch of birch showing work; 6, section of inner bark, showing cyst 

 occupied by the coccid; c, coccids in position, with layer of bark removed, showing waxy secretion, 

 surrounding them and rods of was: protruding from anal tube; d, section of rod of wax, showing its 

 compound nature— a, natural size; c, enlarged; b and d, greatly enlarged (original). 



Small curls of wax are given off from pores thickly scattered over 

 the body of the coccid, but more copiously from the sides, where the 

 excretion becomes consolidated into thick lamina? of white wax. The 

 anal extremity produces numerous stronger waxen curls, and in the 

 midst of these there issues, from the anus itself, a tubular bundle of 

 waxen rods condensed into an apparently solid thread, which does not 

 curl, but forces its way out of the nearest crevice in the bark into the 

 open air. (See fig. 1, c, showing coccids in natural position on bark; 

 and d, which shows section of waxy rod.) In fair weather these glassy 

 hairs may be seen issuing from every crevice in the bedeviled cortex, 



