Chapter XI. 



INSECTS INJURIOUS TO THE WILLOW. 

 Salix of different species. 



Tlie willows harbor a very large insect population, and form the 

 original food-plant of a number of the species at present living at the 

 expense of our fruit trees. 



The number of species in Europe which live upon the willow 

 is said by Kaltenbach to amount to 396. Of this number 94 are Cole- 

 optera, 214 are Lepidoptera, of Hymenoptera there are 40 species, all 

 of them saw-flies eating the leaves; of flies (Diptera) there are 21 

 vspecies, all with three exceptions gall-flies (Cecidomyiae), while the re- 

 mainder consists of Hemiptera, of which 27 iiinds are enumerated, 

 .nearly all of these being Aphids and bark lice. 



It is to be observed that in Europe, as in this country, the number 

 of borers is rather small, willows perhaps ordinarily not being exposed 

 to their attacks, though this may be the result of imperfect observa- 

 tion. Out of 94 kinds of beetles Kaltenbach enumerates about 12 

 Cerambycidse or wood-borers, and only two or three bark-borers, while 

 the greater number of the beetles he enumerates are leaf-beetles. In- 

 deed, the large number of leaf-beetles and saw-flies which prey upon 

 the foliage of willows, both in the old and new World, is a noteworthy 

 fact. 



The number of species of willow insects we enumerate amounts to 

 186, and there is little doubt but that the number will be greatly in- 

 creased by future observations. 



AFFECTING THE TRUNK. 



1. Xylotrechus annosus (Say). 



In the month of April Mr. Coquillett cut down a willow tree and di- 

 vided it up into " sled-lengths," when no traces of borers could be 

 seen ; but early in March of the following year, while cutting this wood 



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