196 THE CANADIAN ENTOMOLOGIST. 



of the wound, and no damage could be seen the following year from the 

 attack. 



With the Prunes it was different ; there was no gumming, and only 

 the very small pin-hole, with its little trail of wood-dust to mark the spot 

 where the little borer was industriously working within ; but six such 

 holes were sufficient to cause the death of the tree. 



The food of these beetles is a fungus grown on the walls of the 

 galleries and chambers made by the beetles, and develops only under 

 certain conditions, namely, when the tree is in a diseased or dying con- 

 dition, and in the case of these fruit trees this condition is brought about 

 by the attack of the beetle itself On each side of the hole for more than 

 a quarter of an inch and extending up and down the body of the tree for 

 from six inches to two feel, and continuing inward as far and as fast 

 as the gallery progresses, the wood of the tree turns brown, and gives off 

 an odour, exactly similar to those conditions arising from the so-called 

 sour-sap disease, and under this condition the Ambrosia seems to develop 

 even better than where the trees seemed to have been attacked, after 

 having partially succumbed to some other cause. 



There seems to be no special time for attack, but from early spring' 

 until late fall I found trees being attacked, and galleries containing beetles 

 in all the stages of development. As to remedies I found all those pre- 

 scribed to be of no avail. Plugging, opening the galleries to the light, 

 external and internal applications, seemed to have no effect. The only 

 remedy, other than that of removing the affected trees and burning, 

 would be a heavy fumigation with hydrocyanic acid gas when the trees 

 are dormant. 



The beetles always enter the tree from the north and east sides, and 

 rarely more than six feet from the ground. Another point of interest is : 

 As soon as a gallery terminated in a chamber, an adult of the colony took 

 up its station at the door of the gallery with the tip of the elytra just flush 

 with the surface of the bark, where it suffered death rather than admit an 

 intruder, for in every case that I inserted a wire I found that this beetle 

 died rather than escape, which it could easily have done by running along 

 the gallery to the chamber. This sentinel also seems to act as garbage 

 man for the colony, removing all excess of wood-dust and excreta not 

 needed in the propagation of the Ambrosia 



A description of this beetle can be found in Bulletin 7, New Series 

 Division of Entomology, U. S. Department of Agriculture, 



