SOME WOOD BORING INSECTS 



BY FRED J. SEAVER, CURATOR, NEW YORK BOTANICAL GARDEN 



OF all the destructive insects, the borers are the most 

 obscure and difficult to control by artificial means. 

 This is due to the fact that they "dig in" and resort 

 to "trench warfare," with the result that during the 

 greater part of their life cycles the insects themselves are 

 unseen, their presence being indicated by the external 

 symptoms only. In some cases these symptoms furnish 

 a very accurate index as to the nature of the trouble, but 



FIGURE 1. HEMLOCK WITH BARK PARTIALLY REMOVED 

 SHOWING BURROWS AND BORERS. ABOUT NATURAL SIZE 

 ALSO AN ENLARGED DRAWING OF THE ADULT BEETLE 



in Other cases they are indefinite and often misleading, 

 even to the expert. With a little experience, even an 

 amateur can become familiar with the more common of 

 the wood-boring insects whose ravages are too well known 

 to many and of interest and importance to all tree lovers. 

 In a general way the wood-boring insects may be divid- 

 ed into two main groups, depending upon their mode of 

 attack. The first of these is the group known as the 

 "bark-borers" or those which work in or just underneath 

 the bark, and the second, the "deep-wood borers," com- 

 prising those forms which j>enetrate deep into the 

 branches or main trunk of the tree. While at first 

 thought the bark-borers might be considered the least 

 injurious, their work is often more likely to prove fatal 

 in a short time than even the deep-wood borers for the 



following reasons : The active growing portion of the 

 trunk of the tree is that just under the bark while the 

 greater part of the wood below this serves merely, to 

 give mechanical strength, and, to a certain extent, as a 

 water conducting system, and is not really essential to the 

 life of the tree except as it serves to support the young 

 branches and carry the leaves up where they can be freely 

 exposed to the sunlight. Since the bark-borers often 

 confine their attacks to the actively growing tissues, when 

 abundant enough to surround the trunk they shut off the 

 circulation of food materials and the entire tree or that por- 

 tion above the point of attack is "girdled" and strangled. 

 The most of the destructive work is done by the cater- 

 pillar or larval stage while the adult which may take 



FIGURE 2. WORK OF THE RED CEDAR BORER, 

 NATURAL SIZE 



ABOUT 



the form of a beetle, butterfly or moth, often serves only 

 as the egg laying stage and feeds sparingly. While the 

 work of the caterpillar has been done in obscurity the 

 adult emerges from its hiding place and is usually pro- 

 vided with wings in order to facilitate the process of 

 mating. The adult stage is usually short lived, and, after 

 mating and depositing the eggs, the female soon dies and 

 the young caterpillars again "dig in," often spending one 

 to several years in the larval stage before reaching 

 maturity. While the adult usually feeds sparingly, in 



