THE SPRUCE INVESTIGATION. 257 



the bark and into the sapwood. The entrance is made by a single 

 female, attended by a male. After she has penetrated into the 

 wood, one or more females are admitted, and each excavates 

 a gallery, branching from the first, while the male remains 

 at the entrance to assist in expelling the borings and to guard 

 against the entrance of their insect enemies. After each female 

 has extended her gallery a short distance into the wood, small 

 cavities are excavated in the sides of the gallery wails. An 

 egg is placed in each of these, and the mouth of the cavity is 

 closed with fine wood borings and cemented with sap and ex- 

 crement. These egg cavities are placed at regular intervals as 

 the gallery is extended, until each female has deposited from 

 ten to twenty or more eggs. Before the first eggs hatch, a pecu- 

 liar kind of fungus, the germs or spores of which are evidently 

 carried from the old brood galleries, gathers on the bodies of 

 the parent beetle, and commences to develop on the walls of 

 the galleries and in the mass of borings at the mouth of the egg 

 cavities, forming a granulated, cheesy mass, called ambrosia. 1 

 The eggs hatch into minute, white grubs, which commence 

 to feed on the ambrosia at the mouth of the egg cavity, and as 

 they grow, they enlarge the cavity to accomodate the increasing 

 size of their bodies. It appears that the young grubs are provided 

 with a continuous supply of the ambrosial food by the parent 

 beetle as she moves back and forth in the gallery. The walls of 

 the gallery becomes thickly coated with the fungus, which with- 

 out the vigilant care of the mother beetle, would completely fill 

 the galleries and smot her the occupants. When the grubs attain 

 their full size, they change to pupa and adults, in the cavities 

 or cradles, which are just large enough to comfortably accom- 

 modate their bodies. After changing to the adult, they come 

 out into the main gallery and either excavate other branching 

 galleries, or emerge to start new ones on nearby trees. Possi- 

 bly two or three broods develop in a single season from the 

 first set of eggs, the later broods remaining in the galleries over 

 winter. 



1 For further and more detailed information see the excellent paper on the subject 

 by the late H. G. Hubbard, Year Book U. S. Dep. Agric., 1896, pp. 421^130. 



