1<AMILY SCOLYTIDAE 



467 



at an aiij^de, subse(}ueiitl\' turninj; and fi^oinj^ straii^ht down towards the 

 heart of the tree. These forms (Hffer in the wa\- in which the; tunnels 

 are eaten out. 



In the first case the female beetle bores down some distance into the 

 sapwood, or the entrance-tunnel may be made by both male and female 

 beetles. The female is then fertilized, and she continues her tunnel, eating 

 out small offset tunnels in which one or more eggs are laid. The larvae on 

 hatching out usualh' feed on fungus matter lining the walls of the tunnel 

 and have therefore been called "ambrosia" feeders. The larvae when full- 

 fed pupate in the offset tunnels, and the beetles when mature crawl into the 

 main tunnel and up it to the outside of the tree. Both male and female 

 beetles as soon as pairing and egg-laying are completed leave the tunnel. 

 This latter, as is also the case with the offshoot tunnels, is completely free 

 of all wood-dust and excreta (cf. fig. 385, Scolytoplatypm, p. 606). 



In the second case the male and female carry the tunnel deep down into 

 the wood, the tunnel going perhaps straight through the bark, taking a sharp 



FlO. 309. — Plans of Egg Tunnels of the Scolytid Wood-borers. /", tunnel down 

 into the sap- and heart-wood ; a^ place where the eggs are laid. 



bend in the outer sapwood, and then going down straight or on a curve or 

 serpentine into the sapwood or into the heart-wood. The tunnel is uniform 

 in width throughout, circular in shape, and has no offset tunnels to it. 

 When deep enough in the wood the female lays her eggs at the bottom. 

 The larvae on hatching out also feed on sap or fungus materials on the 

 walls of the tunnel, and as they increase in size they lie naked in the 

 tunnel one above the other and pupate in this position. When mature 

 the beetles simply crawl up the tunnel and escape from the tree. This 

 tvpe of wood-borer is exemplified by the teak Xylcbonis (fig. 381). Most of 

 the known Platypodidae (figs. 389, 390) oviposit in this manner. 



In the case of the main tunnel with the offsets it is possible to distin- 

 guish the beetle from the plan of the tunnels, but this is not the case with 

 the simple tunnel without offshoots. 



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