FAMILY SCOLYTIDAE 



525 



A <j[eneration of this beetle appears on the wiiif^ about the be^inniiifj^ 



of June from ej^^s laid some time during April by the 



Life History. j:,^eneration of the insect which passed throuf^h the winter 



in the tree. 

 This beetle is a common pest of the piine in Kumaun and the areas to 

 the west, Jaunsar and Tehri Garhwal. The male beetle bores throuj^h the 

 thick bark of the tree, tiiakinj^^ a circular entrance-hole which is usually 



very distinctly seen on the outside (cf. 

 ii,i(. id, which shows several entrance- 

 holes and one in section). This entrance- 

 tunnel leads to an enlarj^ed circular 

 or heart-shaped chamber, the pairing- 

 chamber, which is eaten out either in 

 the bark itself or (where the bark is 

 thinner) in the bast and sapwood. It 

 will not infrequently be found, however, 

 that there is no evidence of this chamber 

 in the sapwood. 



From two to three (or at times four) 

 female beetles enter successively the 

 pairing-chamber and after fertilization eat 

 out each a long gallery in the bast layer 

 of the tree; these are the egg-galleries, 

 and they are carried in opposite direc- 

 tions, or two up and one down (if three 

 females pair with a male), parallel to the 

 long axis of the tree (g in fig. le indi- 

 cates the egg-galleries ; the egg-gallery 

 is either quite straight or it may have 

 small zigzag curves in it or even small off- 

 set prolongations {vide fig. 339), and may 

 be as much as three inches in length. 

 Two or more holes are eaten out by 

 the female beetle through the bark to 

 the outside to allow of air entering 

 the gallery, which is otherwise blocked 

 up its whole length with the loosely 

 packed wood-dust and excreta of the 

 beetle, much in the same way as is the 

 tunnel of P. trcndii. 



The eggs are placed, as is customary 



with these beetles, in small notches eaten 



out in the walls of the egg-gallery. The larvae on hatching out make very 



irregular galleries carried in a direction more or less at right angles to the 



egg-gallery. The galleries are made entirely in the bast la3er, and the 



^^ 



/( 



Fig. 339. — Pairing-chambers and egg- 

 tunnels (containing living beetles) of 

 Polyi^raphus lo)i^i:;ifolia, Steb., in the 

 inner surface of Piniis Unigifolia laark 

 just stripped off the trees. /, pairing- 

 chamber ; e, egg-gallery ; a, aeration- 

 hole ; b, a beetle eating out a gallery. 

 Jaunsar, Noith-West Himalaya. (E.P.S.) 



