INSECT PESTS OF OHIO SHADE AND FOREST TREES 321 



in July, each female making a vertical gallery an inch or more in 

 length and along the sides of which she deposits in small notches^ 

 20 to 50 eggs. The parental galleries are frequently very regularly 

 placed on the tree one above another. The eggs soon hatch and 

 the grubs work in the tissues at first at nearly right angles to the 

 primary galleries, but those at the extremeties soon diverge from 

 the others till ^ they run nearly parallel with the wood fibres. The 

 larval galleries rarely cross each other. Winter is passed by the 

 grubs in a nearly full-grown condition. They transform to pupa 

 during the last of May and the beetles appear about a month later." 

 This species has entered Ohio from the eastern border and is gradu- 

 ally working westward. It may be said to be sweeping the hickories 

 before it as it progresses. (See Plate LXVI, Fig. 2.) 



Food plants. Bitternut, shellbark and pignut hickory and 

 probably pecan are the food plants. 



Distribution. This insect ranges over the entire section of the 

 United States east of the Mississippi River. It is also reported 

 from Canada. In Ohio, it is particularly prevalent in the north- 

 eastern section. In Youngstown great damage has been done in 

 the parks by this insect through the destruction of the hickories. 

 The area of severe injury seems to be working westward gradually. 



Natural enemies. Four hymenopterous parasites have been 

 recorded from the hickory bark beetle : Spathius trifasciata Riley, 

 S. unifasciatus Ashm., Lysitermus scolyticida Ashm., and Bracon 

 scolytivorus Cress. A beetle, Clerus ichneumoneus Fabr., preys 

 upon this species. 



Control. Little is to be done by way of destroying the hickory 

 bark borer after it once gains access to the tree. About the only 

 thing of a practical nature to be done is to remove and destroy trees 

 as soon as they are known to be attacked, or in case only parts are 

 invaded by the beetles to remove those parts. 



THE PIGEON TREMEX 

 (Tremex columba Linn.) 



Description. Diseased or dead trees are preferred by this in- 

 sect, and although rather plentiful it is not of great economic impor- 

 tance. However, the insects quite frequently are observed search- 

 ing about such trees and it is forthwith assumed that they are 

 responsible for the trees' condition. 



The adult pigeon tremex is a beautiful four-winged, wasp-like 

 creature having a wing expanse of about two and one-half inches. 

 The tip of the abdomen is adorned by an appendage which the insect 



