GRASSHOPPERS AND OTHER INJURIOUS INSECTS OF 1911 AND 1912. 



57 



The Bronze Birch Borer. 



The death of so many ornamental birches is al- 

 most entirely due to the work of the grubs of the 

 Bronze Birch Borer (see Fig. 37) . They make bur- 

 rows somewhat similar to those made by the Two- 

 lined Chestnut Borer. Sometimes the attack be- 

 gins at the base of the tree but more often the 

 upper branches are attacked first. 



The adult insect is a beetle about the size of 

 the oak borer just discussed, but the body is bluish 

 brown with no markings on the wing covers. The 

 beetles are found flying during June and the first 

 part of July. Eggs are laid at this time on the 

 bark of the trees, one year being required to com- 

 plete the life cycle. This insect attacks the differ- 

 ent species of birch but seems to prefer the cut-leaf 

 form. It also works on poplars and willows. 



Fig-. 37. Bronze Birch 

 Borer. Ruggles. 



The Elm Borer. 



The worst pest of the American elm in Min- 

 nesota is the yellowish-white footless grub of the 

 elm borer. The presence of dead limbs and dis- 

 eased areas of bark on the trunk of a tree are 

 fairly sure signs that these borers are present. 

 Often these signs are not noticed until the tree 

 starts to leaf out in the spring, following infesta- 

 tion. 



The adult Elm Borer is a grayish beetle about 

 half an inch long. It has three narrow bands of 

 red or orange markings across the wing covers. 

 The beetles are found from June to August and 

 probably eggs are laid on the bark of the elm trees 

 at any time during that period. The eggs hatch 

 into grubs which work beneath the surface. The 

 first year, these grubs or larvse work just beneath 

 the bark and it is here that the most damage is 

 done. The second year they work more deeply 

 into the wood. If numerous in one region of the 

 trunk, they cause the bark to shrink and shrivel 

 at that place. The life history is not fully known. 

 It is probable that it takes three years to complete the cycle. 



Pig. 39. Elm Borer lar- 

 va. About twice en- 

 larged. Original. 



