INSECTS AFFECTING PARK AND WOODLAND TREES 



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under the bark, and each furrow was occupied by one or two beetles. The 

 furrows are excavated from below upwards. In the short ones but one 

 beetle was found, ancL-but one perforation communicating with the external 

 air. In the longer ones two beetles (probably the two sexes), were usually 

 found, and from two to four perforations afforded means of ingress and 

 egress. The lowest perforation, which is the one by which the beetle first 

 enters and commences its furrow, is often found closed or " blocked up " by 

 the dust and debris thrown down by the excavator in the progress of the 

 work. The second perforation is generally one or two inches above the 

 first. I failed to discover whether it is made by the second beetle for the 

 purpose of ingress or by the first beetle. The third and fourth perforations 

 are in a nearly direct line above the other two and are probably made from 

 within outwardly, but for what purpose is uncertain. In one instance the 

 two beetles were found at work making these perforations, boring through 

 from the inner surface of the bark. In one instance the third was less than 

 half an inch above the second, so that there would seem to be no particular 

 necessity for it. The eggs of the insect are deposited along both sides of 

 the upper part of the furrow. They lie close together, almost or quite in 

 contact with each other. When the larvae emerge from the eggs they begin 

 to feed upon the soft cambium and to work their way under the bark at right 

 angles to the main furrow. They are, at first, so minute and work so close 

 together that they make no distinct furrows but seem rather to devour 

 entirely a very thin layer of the cambium. But as they increase in size they 

 begin gradually to form distinct furrows and to take directions more diver- 

 gent from each other and from their original course. In this way colonies 

 from contiguous furrows at length run together and in time the whole trunk 

 is surrounded by their multitudinous pathways, and the death of the tree is 

 accomplished. Great care is taken by the parent beetles to keep their fur- 

 rows separate. No instance was observed in which they ran together. In 

 one instance the course of a furrow was changed to avoid running into the 

 lateral furrows of a colony of larvae just above. No furrows were found in 

 the tree more than 10 or 12 feet from its base, thus indicating that the 

 attacks are made upon the lower part of the trunk. The attacks are not 

 made simultaneously. Some of the furrows in this tree were scarcely more 

 than an inch long, and evidently had been just commenced. Others were 

 fully excavated and contained eggs, and in others still the larvae had hatched 

 and commenced their work, but in none were they fully grown. In another 

 tree, a few rods distant from the first, the attack had evidently been made 

 earlier in the season, for the larvae were farther advanced in size and the 

 bark, on one side of the tree was well loosened, though, strange to say, the 

 other side of the trunk was comparatively unharmed. I was unable to dis- 

 cover why, in this instance, the attack was limited to one side of the trunk. 

 It is pretty evident therefore that the trees are attacked all along during 

 the months of June and July and possibly as late as August. 



