INSECT ATTACKS AND MrSCELLANEOUS 01iSER\ ATIONS. 



THE INSECTS OF THE HEMLOCK. 



[Note. — The following list of insects feeding on the hemlock, together 

 with a reference to amount and character of injury inflicted, was drawn 

 up at the request of Px'ofessor A. N. Prentiss, of Cornell University, 

 for use in the monograph on the hemlock, Tsuga Canadensis, which he 

 had been engaged to prepare for the Division of Forestry, in the U. S. 

 Department of Agriculture. It is understood that his manuscript was 

 some time since presented to the Department, but in the absence of the 

 needed facilities for prompt publication of the labors of the Division, there 

 is no prospect of its early issue. Under the circumstances, in compliance 

 with the request made, Professor Prentiss has kindly given me permission 

 for the present use of the notes communicated to him. A few additions 

 have been made to the paper since its return, and some figui'es introduced.] 



While the statement of Dr. Fitch, that " the hemlock is much the 

 most free from insects of any tree in our country," may not be strictly 

 true, yet its comj^arative freedom from insect attack is'a fact, and one 

 for which no satisfactory reason may be assigned. The j^eculiar pung- 

 ent odor of turpentine is generally thought to be repulsive to insects, 

 and the si^irits of turpentine is not infrequently employed to protect 

 clothing, woolens, and specimens of natural history from the attack of 

 moths, and some of the smaller coleoptera. To some insects it is 

 undoubtedly poisonous, and even its odor is fatal to them. And yet, 

 there are Lepidopterous larvte, as for example, Pinipestis Zinimermani 

 Grote {Bull. U. S. G.-G. Surv. Terr., iv, 1878, p. 700), and Harmonia 

 pint Kellicott {Entomologica Americana, i, 1885, pp. 171-173) which live 

 just within the sap-wood of young and vigorous pines; their bodies 

 are constantly coated with the pitch, it constitutes part of their food, 

 as it is found mingled with their excrement, and their pupal stage of 

 transfoi'mation is undergone within a mass of pitch-exudation upon 

 the bark of the tree. The pines furnish the requisite food for a large 

 number of insects, most of which are limited to them, although a few 

 extend their range to other Coniferw, and to some of the deciduous 

 trees. M. Edouard Ferris has given a list of more than a hundred 

 species which infest the maritime pine of Southern Europe. Dr. Fitch 

 in his Fourth Rejiort on the Insects of New York, in 1858, notices sixty- 

 six pine-feeding insects. Dr. Packard in his Insects Injurious to Forest 



