462 



FAMILY SCOLYTIDAE 



Many species of hark beetles, or in some cases genera only, can be 

 readily recognized by the plans of the galleries made by the mother 

 beetle and her offspring, the larvae, in the bast and sapwood of the 

 tree, or down in the interior of the wood. The female beetle, for 

 instance, after pairing with the male in the pairing-chamber in the bast, 

 grooves out a gallery, called the mother- or egg-gallery, which may be 

 straight or may be serpentine, in the bast and sapwood in a direction 

 parallel to the long axis of the tree. On each side of this gallery the beetle 

 eats out little notches, depositing an egg in each as she goes along. When 

 she has laid all her eggs the gallery ceases, or at most may be continued 

 for a short distance, in which portion she herself dies. On hatching 

 the larvae eat out each a gallery called the larval gallery, which is either 

 more or less at right angles to the mother-gallery, or inclines downwards 

 in the case of the first-laid eggs and upwards in the case of the last-laid, 



I. II. 



FIG. 306. Plans of galleries of Scolytid beetles in bast. I, Monogamous; 

 II, Polygamous, a, egg-gallery ; b, larval gallery ; c, pupating-chamber ; 

 if, aeration hole ; e, pairing-chamber. 



being more or less at right angles from those eggs laid about the centre of the 

 mother gallery. The larvae continue eating out their galleries, which usually 

 serpentine to some extent, till they have reached full development in size. 

 They then enlarge the end of the gallery either in the bast and sapwood 

 or entirely in one or the other, and pupate in this chamber. On maturing, 

 the^beetle bores straight out through the layer of bark over it, taking the 



