1893-] ENTOMOLOGICAL NEWS. 



DEPARTMENT OF ECONOMIC ENTOMOLOGY, 



Edited by Prof. JOHN B. SMITH, Sc. D., New Brunswick, N. J, 



Introduction of Predaceous Insects. In " Science," No. 509, for Nov. 4, 

 1892, Mr. Camillo F. Schaufuss, gives an account of the efforts made by 

 Mr. A. D. Hopkins, of the Virginia Station, to collect and introduce into 

 our country the European Clerus formicarms L. to assist in destroying 

 the Scolytids which are so injurious to Virginian forests. Mr. Schaufuss 

 considers the experiment a promising one, and sees no reason why it 

 should not prove successful. There seems no real reason, perhaps, win- 

 it should not be; but it would not be well to anticipate too much. There 

 would seem to be no reason why our allied American species should not 

 increase sufficiently to control the Scolytids, but they do not seem to do 

 so. There is not even proof that Clerus formicarius in its own home is 

 in itself a large factor in controlling Scolytids. The thorough forestry 

 organization of Germany is alone sufficient to minimize injury; the re- 

 moval of every diseased or infested tree; the systematic collection of 

 fallen branches; the utilization of absolutely everything not needed by 

 living trees, is exactly what intelligence would dictate, and, where the 

 destructive insects themselves are placed at so great a disadvantage, pre- 

 daceous insects may be relatively much more numerous and effective. 

 The result of the experiment will be watched with interest. 



It is perhaps a trifle unfortunate that Dr. Riley's experiment, the intro- 

 duction of Vedalia to destroy Icerya was so splendidly and rapidly suc- 

 cessful. The success has become so widely and generally known that it 

 seems to have become a fixed idea with many that all sorts of injurious 

 species can be controlled in the same way. I have been asked many 

 times by all sorts and conditions of men why I don't try to do something 

 of that kind for our common pests. Dr. Riley's experiment was made 

 under unusual circumstances, and on a strictly scientific basis, with all the 

 chances in his favor. He had to do with an introduced insect, which, in 

 its own home, was not particularly abundant or destructive. He reasoned, 

 correctly enough, that if it could be discovered why the insect was rare at 

 home and abundant here, the conditions might be made more similar. 

 The working out of the problem deserves all possible praise, and the suc- 

 cess was signal. The natural enemy was discovered, its history was made 

 out, and it was introduced, propagated and colonized. The insect was 

 only asked to do here what it had already done at home, and was placed 

 in surroundings where Icerya only was familiar to it as prey. The same 

 combination of circumstances may not occur again for years in favor of 

 an experiment of that kind. 



This should not be read as an adverse criticism of Mr. Hopkins' ex- 

 periment, but rather as a warning that too much must not be expected 

 of natural enemies. Nature never works to the immediate destruction 

 of its creatures; the balance is so nicely adjusted that no rapid and per- 



