2 BULLETIN 437, U. S. DEPARTMENT OF AGRICULTURE. 



FOOD PLANTS. 



Both deciduous and coniferous trees, as well as shrubs and herba- 

 ceous plants, are attacked. Some genera attack only deciduous 

 trees, some only conifers, while others attack both. Plants of any 

 age may be attacked and any part of the plant from the roots to the 

 leaves, but the principal part is the bark and wood of the main 

 trunk. 



CHARACTER OF THE WORK. 



The borer work or injury consists of a flattened, oval, gradually 

 enlarging, more or less tortuous mine or wormhole (PI. VIII, 

 figs. 1, 2), which, when completed, widens out into an elongate 

 oval pupal cell. This cell connects with the outer surface by a short, 

 oval exit hole. The mine has its surface marked by fine, transverse, 

 crescentic lines and is usually tightly packed with arc-like layers of 

 sawdust-like borings and pellets of woody excrement. The injury 

 may be entirely in the bark, entirely in the wood, or, as is usually 

 the case, in both bark and wood. 



LIFE HISTORY. 



All bark and wood boring flat-headed borers hatch from eggs de- 

 posited by the mother beetle singly or in a mass (PI. IX) , on the bark 

 or tucked in some crevice in the bark or wood or under the bark at 

 the edge of a wound. Each larva mines the inner bark or wood 

 until it reaches maturity, when, after mining outward nearly to the 

 surface, it retreats into its mine and forms an oval cell, in which it 

 pupates and transforms to an adult beetle. The beetle rests awhile, 

 then bites its way out, feeds on the bark, foliage, or pollen of some 

 plant, usually its host, and then mates. The female, after depositing 

 eggs to start a new generation, soon dies. 



SEASONAL HISTORY. 1 



The egg is usually laid in the spring or summer and the borer 

 hatching from it feeds and rests until the following fall, or the second 

 fall, or even the third fall, before it reaches maturity. It then 

 either rests over the winter in the larval stage and pupates and trans- 

 forms to the adult the following spring, or it pupates and transforms 

 to the adult in the summer or fall and rests over the winter in the 

 adult stage in the pupal cell. Most of the bark-borers pass the 

 winter in the larval stage and emerge soon after pupating and trans- 

 forming to adults in the spring. Many of the wood-borers pupate 

 and transform to adults in the summer or fall and pass the winter 



i Some evidence has been obtained which indicates that certain species may pass the winter in the egg 

 stage. Mr. A. B. Champlain collected a mass of eggs at Colorado Springs on February 12, 1914, which 

 produced young Chalcophora larvse. Certain A grilus larvae feed in the spring a short time before pupatings 

 and transforming. Individuals of some species pass the winter in the pupal stage. No obs ervation 

 have been made which would indicate that the adults live over the winter after they have emerged. 



