THE ELM. 



115 



shewn the importance of watching the habits of an 

 insect less than a quarter of an inch in length. 

 The result of their observation is that the perfect 

 insect feeds on the inner bark of the Elm, to reach 

 which it perforates the outer bark, and feasts at its 

 leisure. The cavities thus made interrupt the as- 

 cent and descent of the sap, and retain moisture, 

 from the combined effect of which causes the tree, 

 in the course of a few years, becomes sickly, and 

 is brought into exactly that state in which the fe- 

 male selects it for laying her eggs ; though some- 

 times she attacks a tree which is beginning to 

 decay from other causes. A suitable tree having 

 been selected about July, she perforates the bark, 

 and eats away a vertical passage about two inches 

 in length, laying from twenty to fifty eggs as she 

 advances. Having 

 completed her task, 

 she dies. About two 

 months afterwards the 

 eggs are hatched, and 

 the grubs immediately 

 begin to eat their way 

 also through the inner 

 bark in a horizontal 

 direction, some to the 

 right and some to the 

 left, but never inter- 

 fering with each other's 

 track. When each 

 grub has finished its 

 course of eating, it 

 turns to a pupa and 

 then to a beetle; after which it gnaws a straight 

 hole through the bark, and comes out about 



