THE PINE INVESTIGATION. 



405 



Fig. LXXII 

 pentine tube at 

 entrance of gal- 

 lery of Dendroc- 

 tonus frontalis . 



their followers, that find, in the weakened vitality of the tree 

 and lessened flow of turpentine, but slight obstruction to the 

 prosecution of their work to completion. 



In the formation of the brood galleries, the 

 same process is followed as that just described, 

 and may often have the sairie character as pre- 

 liminary galleries, but as the flow of turpentine 

 ceases, the course of the gallery is changed or 

 reversed, and is extended to completion in a 

 more or less longitudinal direction, forming 

 graceful curves to the right and left, so that the 

 long fibers and cells of the inner layer of bark 

 are severed at intervals of every one or two inches 

 Tur along its track, as shown in Fig. LXI1. 



In the excavation of the gallery, the beetles 

 utilize the main entrance only so long as it is 

 convenient for them to eject the boring and turpentine 

 through it, since as soon as they have proceeded one or two 

 inches through the inner bark, they commence the excavation 

 of a side entrance in the roof of the gallery and fill the main en- 

 trance and gallery to that point with the borings, which, being 

 mixed with turpentine, form a hard impenetrable mass. These 

 side entrances are excavated at intervals of one-half to one or 

 more inches, Fig. LXII1. The first is usually filled with the 

 borings from the second, and so on ; so that there is an opening 

 to the surface at all times near where the beetles are at work. 

 Pits varying in depth, but not extending to the surface, are 

 often excavated at intervals of one-fourth to one-half inch be- 

 tween the side entrances, which are evidently occupied by one 

 sex while the other is at work excavating. These are also fill- 

 ed with borings when not in use for other purposes. 



After the excavation of the entrance and preliminary gallery 

 is accomplished, and about the time the first side entrance is 

 commenced, the female commences to deposite her eggs in 

 small cavities in each side of the gallery, at intervals of one- 

 eight to one or more inches until the brood gallery is complet- 

 ed. In each of these cavities a single egg is deposited, and se- 



