THE COTTONWOOD BORER. 5 



November, 1913, and January and February, 1914, the larvas that 

 hatched in 1913 varied in length from 0.70 inch (1.75 cm.) to 1.0 

 inch (2.5 cm.). B}^ September, 1914, they had grown to 1.20 inches 

 (3.25 cm.) and 2.0 inches (5 cm.). By the spring of 1915 nearly all 

 were more than 1.60 inches (4 cm.) long, some reaching 2.20 inches 

 (5.5 cm.). 



During the second winter the larvae occupy large tunnels that 

 reach from the inside of the bark near the ground level to the bark 

 several inches below. Both ends of the tunnel are plugged with 

 excelsiorlike fibers of wood, the larva resting on the lower plug. In 

 the spring, before transforming to the pupa, the larva cuts through 

 the bark at the upper end of the tunnel, and plugs the openings 

 with wood fibers. 



TIME AND PLACE OF PUPATION. 



In 1914 pupae were secured on June 23. Of the larvae reared from 

 the 1913 material, one was found as a pupa when examined on July 3, 

 1915. Another was found as a dead pupa a few days later. 



The pupa rests back downward on the fiber plug at the lower end 

 of the tunnel which was occupied by the larva during the second 

 winter. 



EMERGENCE OF ADULT. 



One adult, which was reared from a larva hatched in 1913, 

 emerged on July 13, 1915. In 1914 adults emerged from 12 screened 

 trees from July 8 to August 4. However, as noted, eggs were se- 

 cured that had been deposited about July 4, which indicates that 

 emergence occurred during the last of June, and one report was 

 received on June 16 that adults had been seen several days before. 

 The period of emergence thus computed is about 50 days. 



NATURAL ENEMIES. 



Several young larvae were foimd dead, overgrown with a fungus. 

 No instances of parasitism were observed during the investigations. 



METHODS OF CONTROL. 



The desirability of developing control measures will be under- 

 stood from a perusal of the following figures. On September 15, 

 1913, the bases of 10 trees that varied in diameter from 4 to 8 

 inches were examined for eggs and larvae. The number of eggs, 

 small larvar;, and large larvae, and of the tunnels that penetrated too 

 deeply irilo the wood for their extent to be ascertained . ai-e shown 

 in Table I. 



