THE CANADIAN BNTOMOLOGIST, lO.' 



nr. 



Freijuenily a number of primary-tunnels, not always cut by the same 

 individual, radiate from a common "nuptial-chambei" situated just beneath 

 the common entrance-hole. In such cases, at least with some species, tke 

 male cuts the entrance-hole, the nuptial-chamber and often the beginnings 

 of three or four primary-tunnels. The male is then joined by one or 

 more females, which finish the primary-tunnels and the egg-niches • the 

 work of the male after the entrance of the females consists mainly in 

 removing the chips and refuse and guarding the entrance-hole. 



When the primary-tunnel is long, as is the case, e. g., with several 

 species of Tomicus, there may be one or more ''ventilation holes" through 

 the bark. 



After the labours of egg-laying are over, the adults of some species of 

 Bark-beetles cut irregular, winding " food-tunnels," deeply engraving the 

 sap-wood. Some species hibernate in their food-tunnels, and others in 

 short burrows apparently cut for the purpose. 



A number of species hibernate as larvie, some as pupae, others as 

 adults, and with some species all three stages may be found in the burrows 

 during the winter. 



The Bark-beetles include by far the largest number of our North 

 American species. 



(To be continued.) 



THE AMBROSIA BEETLE (XYLEBORUS XYLOGRAPHUS, 

 SAY), AS AN ORCHARD PEST. 



BY O. E. BREMNER, SAN FRANCISCO, CALIFORNIA. 



During the early si)ring of 1904 my attention was called to the injury 

 being done to Peach and Prune trees in the Dry Creek Valley, Sonoma 

 County, California, by a minute beetle which proved to be one of the 

 Ambrosia Beetles, Xyleborus xylographus, Say. 



The most interesting fact to me was the nature of the attack, for 

 contrary to all former reports of the depredations of this beetle, I found it 

 attacking perfectly healthy Peach trees, and also Prune trees in a perfectly 

 healthy state, as well as those which seem to be sufiering from an excess of 

 moisture, heat or cold, as the case might be. In the case of the Peach 

 trees there was a marked exudation of gum, but this did not seem to 

 hinder the onward work of the borer, but did, however, prevent the 

 mouth of the gallery from being kept open, which resulted in the healing 



June, 1907 



