104 



FOREST ENTOMOLOGY. 



and the male remains near the entrance. The mother-gallery, fig. 

 95, is double-armed. The total length of the mother-gallery (includ- 

 ing both arms) is about 4 to 6 inches when made in the stem, and 

 about li to 2 J inches when made on the pole. Mr A. C. Forbes, 

 who has studied very carefully the life - history of this insect, 1 

 found that the female first bores one half of the arm, and then 

 proceeds to work the other half. The eggs are laid right and left, 

 and are rather variable in number. When found on the stem of 

 a comparatively large tree, they often amount to 120, but when on 



the pole, half this number 

 may be found. 



The larvae commence 

 hatching out about the 

 middle of April or begin- 

 ning of May. At first they 

 are of a slightly reddish 

 colour, but the fully de- 

 veloped larvae are white, 

 with dark head and jaws, 

 and tapering to a blunt 

 point at the end. The 

 larval galleries are about 

 1J inch in length on the 

 stem, and about | to 1 

 inch long in the pole. The 

 perfect beetles emerge about 

 the first week in August, 

 through individual exit-holes, and the bark consequently looks as if 

 it had been riddled with shot. 



The perfect beetles then betake themselves to healthy ash-trees 

 or newly felled ash logs, where they hibernate for the winter, 

 and emerge in March or April. It is very questionable if they 

 do any harm to the standing trees, as they simply bury them- 

 selves in the bark, though Judeich and Nitsche give a figure of 

 " bark roses " resulting from the beetles hibernating, which in all 

 probability is the work of the fungus known as Nectria clitissima 

 following in the train of the bark puncture or wound made by 

 the beetle. 



Fig. 95. Markings of Hylesinus fraxiui on ash stem 

 after removal of bark. 



1 See Trans. High, and Agr. Soc. Scot, 1899. 



