GRASSHOPPERS AND OTHER INJURIOUS INSECTS OF 1911 AND 1912. 



55 



and there lay eggs in the bark. The eggs hatch into the borers 

 which continue the destructive work. 



The region principally involved in Minnesota extends over the 

 southeastern portion of the State from Albert Lea to St. Cloud. A 

 proportion of the trees die from disease. Many unquestionably die 

 from insect work. 



Hearty co-operation to check insect ravages is imperative It 

 may be voluntary if possible, or enforced by legislation if neces- 

 sary. The situation is especially urgent in cities where shade trees 

 are so desirable. Prompt preventive and remedial measures must 

 be resorted to. 



Boring insects cause most of this injury. The more important 

 are briefly described in this circular. Some preventive and com- 

 bative measures of general application are briefly stated. 



The Two-lined Chestnut Borer. 



The white, flat-headed grubs of the Two-lined 

 Chestnut borer in Minnesota kill more oaks than 

 any other species of insect so far discovered. The 

 grubs make burrows beneath the bark in the grow- 

 ing layer. As these tunnels run for the most part 

 across the grain of the wood, the 

 food supply from leaf to root is 

 cut ofl" and next spring the tree 

 thus girdled dies. One or two 

 grubs in a tree would not cause 

 death but where there are many 

 of these burrows crossing and 

 interlacing under the bark, the 

 tree has no chance to recover. 

 These burrows may occur any- 

 where from the base of the tree 

 to the smaller limbs. 

 The adult insects are slender beetles about 



three-eights of an inch long. A light line runs 



lengthwise on each wing cover. They are found 



flying during the last of May, June and the flrst 



part of July. Eggs are laid at this time on ^',fuf Boiler adSt. About 



the bark. They hatch into the grubs which bur- Twice enlarged. Ru..les 



row and make the mines as described. One year is necessary for 

 the life cycle. (The period from the time the egg is laid until the 

 adult insect emerges is spoken of as a life cycle.) 



Fig. 35. Two-lined 

 Chestnut Borer 

 larva. About twice 

 enlarged. Ruggles. 



