THE CANADIAN ENTOMOLOGIST. 25 



would appear that the older adults of the broods excavate branching 

 chambers in which new broods are developed, and that in these old and 

 new chambers they all pass the winter. 



Enetnies. 



A number of predaceous beetles and their larvae may find their way 

 into the brood-chambers at unguarded moments and destroy a portion or 

 all of the colony. This, like other species of ambrosia beetles, appears to 

 be aware of the danger from this source, at any rate, from the time the 

 first eggs are deposited until all the individuals of a colony have 

 developed and emerged from the brood-chambers, one or more adult 

 females serve on guard duty at the entrance, where their armed elytral 

 declivity (as shown in Plate 2, fig. 7 ; Plate 3, fig. 9) completely fills the 

 entrance gallery, thus presenting an impenetrable barrier against intruders. 

 It is therefore only at unguarded moments that the enemy can enter, 

 except, perhaps, the very young, microscopic larvae of the predaceous 

 beetles, which may possibly pass the sentinels unobserved. This guard 

 duty is an interesting feature of intelligence in the habits of all Scolytids. 

 In the case of bark beetles and other species in which the sexes are about 

 equally divided, the male is the sentinel, while the female excavates the 

 brood gallery. Perhaps there is no better example of unselfish devotion 

 to paternal duty than the male bark beetles, since they not only spend 

 their lives on guard, but die at their posts in order that their dead bodies 

 may continue to blockade the entrance to the brood galleries. In 

 Xyleborous, and others in which the females greatly predominate, one 

 or more females serve on guard duty. 



The excessively crowded brood-chambers doubtless offer favourable 

 conditions for diseases, which may, as indicated by evidence before me', 

 destroy an entire colony. 



delation of the Insect to the Health of the Trees Infested by It. 



Eichhoff- was undecided as to whether or not the species did any 

 damage to the trees infested by it, but mentioned that it might prove 

 destructive to orchards or nursery trees. Hubbard^ states that it " breeds 

 only in dying trees," but does much injury to the timber, causing defects 

 in the wood, and the writer^ mentioned that it probably hastens the death 



1. In a brood-chamber before me a number of dead larva? and pupK are found, 

 which have evidently died quite recently from a disease of some sort which cannot at 

 present be studied or determined. 



2. European Bark Beetles, 1. c. 



3. Ambrosia Beetles of North America, 1. c. 



4. Bull. 31, W. Va. Agri. Expt. Sta., 1. c. 



