88 OUR HOUSEHOLD INSECTS 



estate in Norfolk. It seems probable, however, that the 

 Sirex must not be charged altogether with this whole- 

 sale destruction ; the insects appear to have a tendency 

 to attack trees that are already enfeebled by disease or 

 damage, instead of those that are vigorous and healthy, 

 and, therefore, perhaps in some cases they merely accele- 

 rate a death which could not have been long delayed. 

 Still, of course, when they do attack a tree, they often 

 utterly spoil the wood as timber by their numerous 

 burrows in all directions. As an instance of this, we 

 may take a tree that was found in Bewdley Forest some 

 years ago. Twenty feet of the length of this tree was 

 so perforated by this insect as to be completely useless 

 as timber, and serviceable for nothing but firewood. It 

 was transferred to an outhouse, and while lying there 

 for some months, the insects emerged from their bur- 

 rows at the rate of some five or six a day. It is curious 

 to note that the first specimens hatched were chiefly 

 males, but, as time went on, the females became more 

 numerous and the males less so, till at last only females 

 appeared. 



