388 



YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 



of some species, or of the larval stage alone of others. In the former, 

 the adult beetles deposit their eggs in burrows or galleries excavated 



for the purpose, as in figures 48 

 and 49, while in the latter (tigs. 

 50 and 51) the eggs are depos- 

 ited on or beneath the surface 

 of the wood. The grubs com- 

 plete the destruction by boring 

 through the solid wood in all 

 directions and packing their 

 burrows with the powdered 

 wood. When they are full 

 grown they transform to the 

 adult and emerge from the in- 

 jured material through round 

 holes in the surface. Some of 

 the species continue to work in 



FIG. 50. Work of powder post beetle, Lyctus 

 striaius, in hickory handles and spokes: a, 

 larva; 6, pupa; c, adult, natural size; d, exit 

 holes; e, entrance of larvse (vents for borings 

 are exits of parasites): /. work of larvse; g, 

 wood, completely destroyed; h, sapwood; i, 

 heart wood. (Original.) 



FIG. 51. Work of powder post beetle, 

 Xyletinus paltatus, in old pine flooring: 

 a, work of larvse; b, exit holes made )>y 

 emerging broods; c, adult, natural size 

 (Original.) 



the same wood until man} r generations have developed and emerged, 

 or until every particle of wood tissue has been destroyed and the avail- 

 able nutritive substance extracted. 



