Plant Sanitation. 



444 



[May, 1909. 



factors governing the relations between 

 a predaceons insect and its prey that are 

 not yet fully understood. 



The opinion of several leadiug entomo- 

 logists to whom I applied were distinctly 

 contradictory. Some of them considered 

 that the Clerus was of an adaptable 

 nature and would probably be content 

 in this country, so long as the food 

 supply was abundant. Others were as 

 confident that the experiment was 

 foredoomed to failure. They all con- 

 curred in assuring me that the insect 

 was purely insectivorous, and that — 

 failing its natural food — it would die 

 out. Under these circumstances, and 

 seeing that the introduction would be 

 practically costless, I considered the 

 experiment to be worth a trial. 



I gather, from correspondence con- 

 ducted by the Acting Entomologist 

 during my absence, that this par ticular 

 insect (Clerus formicaritis) was selected 

 for experiment on the strength of 

 reports made by Mr. Hopkins of the 

 U.S. Department of Agriculture. It 

 should be understood, however, that 

 Mr. Hopkins was endeavouring to find 

 a natural enemy of a pine-wood borer 

 living in America under conditions 

 practically similar to those found in 

 Northern Europe (the home of Clerus 

 forniicarius). I append a summary of 

 these reports : — 



1. At a meeting of the Entomological 

 Society of Washington, held October 

 6th, 1892, "Mr. Hopkins gave an account 

 of a recent visit to Europe for the pur- 

 pose of studying certain Seolylidce in- 

 jurious to pine trees. He had brought 

 back with him a large number of speci- 

 mens of the European Clerus for u vicar ins 

 alive for the purpose of introducing 

 them into pine forests in West Virginia 

 infested by Dendroctonus frontalis." 



2. In an article on " Damage to 

 Forests by the destructive Pine Bark- 

 beetle," ('Insect Life,' Vol. V., p. 188), 

 Mr. Hopkins remarks that :— "By corre- 

 spondence with Mr. Eichoff, Oberforster, 

 Strasburg, Germany, I learned that a 

 certain beetle, Clerus forniicarius, L., 

 was a great destroyer of Scolytids in 

 the forests there, and from my know- 

 ledge of the habits of the nearly related 

 species, Thanasimus dubius, Fab., I felt 

 that it would be a most desirable species 

 to introduce into our forests to feed 

 upon the ' Destructive Pine-Bark Beetle," 

 and possibly check its ravages. There- 

 fore, the experiment of introducing this 

 beneficial European species into our 

 State for this purpose was recommended 

 to our Station officials and to owners of 

 the threatened Spruce and White Pine 



forests. The proposed experiment was 

 at once approved, and the Station, aided 

 by liberal contributions from four of the 

 principal lumber companies, sent me to 

 Europe in quest of such insects as, in 

 my judgment would, Avhen introduced 

 into our forests, accomplish the desired 

 end. I, therefore, proceeded at once 

 to Germany, and after visiting some 

 of the principal Pine and Spruce forests 

 of Alsace-Lorraine and Saxony, in Ger- 

 many ; Schyz, Lucerne and the Oberland 

 Bernese Alps in Switzerland, I started 

 back to America with over one thousand 

 live specimens of Clenis forniicarius, 

 which was found to be especially des- 

 tructive to various bark beetles in all 

 of the forests visited. After my return 

 here, I found that the European species 

 would readily attack and devour the 

 Destructive Pine-bark Beetle, as well as 

 other bark beetles nearly related to it. 

 From what I have observed and learned 

 of this European bark-beetle destroyer, I 

 am confident that under proper manage- 

 ment it will check the ravages of the 

 destructive pine-bark beetle, and that 

 this enemy of Scolytids will, in time, 

 prove a valued protector of the pine and 

 spruce forests of this country." 



3. In another article by the same 

 author, ('Insect Life,' Vol. VI., p. 126), 

 is noted the reasou for the selection of 

 this particular insect :— " Out of quite a 

 number of enemies of Scolytids observ- 

 ed and considered, only one, Clerus 

 forniicarius, was selected, primarily on 

 account of its being regarded as the 

 greatest destroyer of European bark 

 beetles ; secondly, on account of the 

 general opinion of entomologists and 

 forest officials whom I consulted, and my 

 own convictions from a personal study 

 of its habits, that it would not be inju- 

 rious.", . . "The imported Clerid does not 

 confine itself to one or two species of 

 bark beetles in one kind of trees, but 

 the adults, it would seem, will attack 

 and devour the adults of any species 

 of bark and timber beetles found in 

 the United States, and their larvse will 

 feed on the egg, larvse, pupae, and 

 young beetles of any species infesting 

 the bark of pine and spruce trees." 



It appears that, within a few months 

 of the liberation of these insects, there 

 was a most remarkable diminution in 

 the damage to pine forests in America. 

 Many people, not unnatuarally, jumped 

 to the conclusion that this disappearance 

 of the pest was due to the activity of 

 the imported Clerus. But this was one 

 of those coincidences that so often 

 lead to mistaken deductions. Referring 

 to this particular incident, the late Prof. 

 Riley remarks ('Insect Life,' Vol. VI. , 



