84 ENTOMOLOGICAL SOCIETY OP ONTARIO. 



The clearest explanation of this sudden change is that the species was practically 

 killed out by the exceptionally severe cold of last winter, since such was the case with 

 several other insects. Now, folio iving so closely on the introduction by Mr. Hopkins of 

 Clerus forrnicarius, how easy it would have been to attribute the sudden decrease to the 

 work of the introduced Clerus, had not the decrease been so general and extensive as 

 absolutely to preclude any such possibility. In like manner a certain scale insect 

 {Aspldiotus tenebricosus) had become exceedingly destructive to the soft maples in the city 

 of Washington last year, whereas the present year it is almost entirely killed ofi, evidently 

 by the same exceptional cold. Many of the affected trees were painted with whitewash, 

 with a view of destroying the Aspidiotus, and the death of this last might have been 

 attributed to the treatment (and naturally would be by those employing it) were it not 

 that the same result was equally noticeable on the trees not treated. Reports from 

 southern California would indicate that the Red Scale {Aspidiotus auraniii) is, in many 

 orchards, losing its destructiveness through agencies other than its insect enemies, and 

 in this case the facts are particularly interesting because of the ease with which its disap- 

 pearance may be attributed to some of the recent introductions from Australia. 



The other law that is worth considering in this connection is that experience has 

 shown that, as a rule, the animals and plants of what is known as the Old World — i.e., of 

 Europe and Asia — when introduced into North America have shown a greater power of 

 multiplication than the indigenous species, and in a large number of instances have taken the 

 place of the native forms, which have not been able to compete with them in the struggle 

 for existence. The converse propo.sition holds equally true, viz , that our species when 

 taken to Europe, do not hold their own against the European indigenes. This is still 

 more true of the species introduced from the Old World, as well as from America, into 

 Australia, where the advantage of the introduced forms, as compared with the indigenous, 

 has been in many cases still more marked. All other things being equal, therefore, we 

 should expect the species which are beneficial in Australia to be less so when brought to 

 this country, a deduction which brings out still more clearly the exceptional nature of the 

 case of Vedalia and Icerya, just as there are some notable exceptions, as in the case of 

 the Grape Phylloxera, in the introductions between Europe and America. 



There are some instances in which there can be no doubt whatever as to the good 

 which would flow from the introduction of beneficial species, and an illustration is 

 afforded in the Capri-fig insect, Blastophaga psenes. There can be no question as to the 

 good which would result from the introduction of this species from Smyrna into those 

 sections of California where the Smyrna fig is grown without its intervention, and there 

 are other similar instances which promise well and involve no risk. But I have said 

 enough to show that the successful utilization of beneficial insects is by no means a simple 

 matter and that discriminating knowledge is required to insure success, especially in the 

 second category dealt with in this paper. Wherever the importance of the matter leads 

 to legislation what are denominated " political " methods are apt either to control or in 

 some way influence the resulting efforts — too often with unfortunate consequences. We 

 should, as economic entomologists, be on the alert for special cases where the introduction 

 or dissemination of beneficial species promises good results, and do our best to encourage 

 an intelligent public appreciation of such special cases, while discouraging all that is of a 

 sensational nature, as likely to mislead and ultimately do our profession more harm than 

 good. 



THE ECONOMIC VALUE OF PARASITES AND PREDACEOUS INSECTS. 

 By John B. Smith, Sc.D., New Brunswick, N.J. 



At the very outset I wish to disclaim all intention either of producing a treatise on 

 parasitism in general or disputing the importance of parasites in nature. No one can 

 realize more than I do how much parasites maintain the balance and check the increase 

 of injurious species. I am perfectly aware that were it not for parasites many an insect 

 would become so abundant that certain crops could not be satisfactorily grown. Fully 

 realizing, therefore, the place and importance of these parasites, I feel at the same time 



