502 



FAMILY SCOLYTIDAE 



larva has pupated before the first cold of winter sets in it will probably be 

 killed off during the winter months. The over-wintering beetles leave the 

 trees about the third week in April, and commence ovipositing in the 

 branches of old trees or in the main stem and thicker branches of seedlings, 

 saplings, and small poles. The blue pine and spruce are the trees chiefly 

 preferred, but the beetle also infests the deodar in areas where the former 

 species are not in sufficient abundance. 



The male beetle bores its way through the outer bark down to the bast, 

 and in this and the sapwood eats out a chamber of irregular pattern, which is 

 the pairing-chamber (fig. 328, p). Only parts of the tree covered with thin bark 

 are selected by the beetle, and consequently this insect is never found in the 



FIG. 328. Plan of galleries of Polygraphiis major, Steb., in the sapwood 

 of blue pine. A, In the main stem of poles ; B, in the side branches, where 

 the egg-tunnels are longer. The larval galleries only groove the wood 

 faintly, p. Pairing-chamber ; e, egg-gallery ; /, larval gallery ; d, pupating- 

 chambers in wood. North-West Himalaya. (E. P. S.) 



main bole of the tree where it is covered by thick bark. This fact is one of 



considerable importance in the life history of and the damage done by this 



Three female beetles (occasionally the number may be four or even 



,' enter the pairing-chamber through the tunnel made by the 



male (the first enlarging it slightly), and, after being fertilized by the male, 



to excavate their egg-galleries. Each of the females eats out one such 



gallery (fig. e) and each takes a different direction to that taken by the 



