74 N. S. ENTOMOLOGICAL SOCIETY 



THE INTRODUCTION OF THE PARASITES OF THE BROWN 

 TAIL AND GIPSY MOTHS INTO CANADA. 



Leonard S. McLaine, Dominion Entomological Laboratory, Fredericton, N. B. 



IN order to understand the reason why the Dominion Government has gone to the 

 expense of introducing the parasites of the brown tail and gipsy moths into Can- 

 ada it is necessary to review briefly the history of these two insects in the United 

 States. 



In 1869 a French scientist, who was experimenting with silk worms at his labora- 

 tory near Boston, imported some gipsy moth eggs clusters. During the summer some 

 of the caterpillars escaped. Nothing further was heard of this insect until the late eighties 

 when it had become thoroughly established and was doing a considerable amount of 

 damage to the shade and forest trees in the vicinity of where it escaped. The property 

 owners soon began to realize that the presence of the gypsy moth caterpillar in large 

 numbers was rapidly reducing the value of their property by driving tenants away. 

 They appealed to the State for aid, and in the early nineties the State authorities start- 

 ed suppressive measures. This work was so thoroughly and conscientiously carried out 

 that in 1900, it looked to the average citizen as if the gypsy moth had been exterminated 

 and in spite of the strenuous objections of the Gipsy Moth Commission the State Legis- 

 lature refused to make any further appropriations and the extermination work was called 

 to a halt. From 1901 to 1905 the gipsy moth increased at such an alarming rate that 

 in the latter year the State had to make a special emergency appropriation to meet the 

 now v,ery critical situation. As soon as the work started a preliminary survey was made 

 and it was found that the gipsy moth had spread over twenty-five hundred square 

 miles. All hopes of complete extermination were now lost and every effort was expend- 

 ed to prevent further spread and reduce the heavier infestations. In 1906 the United 

 States Federal Government realized that this pest was a national menace and made 

 their first appropriation for the work. This insect, in spite of all efforts, has now spread 

 into the States of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island 

 and Connecticut. Furthermore it is less than fifty miles from the Canadian border. 



The history of the brown tail moth is very similar to that of the gipsy moth with 

 the following exceptions. The female gipsy moth cannot fly, whereas the female brown 

 tail moth is capable of flying or being carried by the wind great distances, consequently 

 this latter insect has spread over a much larger area than the gipsy moth and has infest- 

 ed the Provinces of Nova Scotia and New Brunswick for some years. In 1891 some 

 brown tail winter webs, containing the hibernating caterpillars, were accidentally im- 

 ported on a shipment of French nursery stock and forwarded to a Boston suburb. 

 This insect soon became established and spread very rapidly. 



When the artificial control work, that is the cutting off and destroying of the brown 

 tail webs, the treating of the gipsy egg clusters and the spraying of the trees with poison 

 to kill the caterpillars of both species, was resumed in 1905 against these two insects, it 

 was soon seen that this method was not sufficient in itself to bring about the complete 

 control of these insects. Furthermore, the cost of treating the large forest areas into 

 which they had now spread made it prohibitive. A study of native insects revealed the 

 fact that they were kept under control, to a great extent, by the presence of natural 

 enemies in the form of parasitic and predaceous insects which preyed upon them. This 

 was not true in the case of the gipsy and brown tail moths in New England at this time 

 and whether this was due to the fact that the natural enemies had been left behind or 

 could not withstand the different climatic conditions could not be determined. In- 

 vestigators were sent to the native homes (Europe) of these insects to study their na- 

 tural enemies. They reported that although outbreaks of both these insects occurred 

 from time to time they were largely controlled by natural enemies. Arrangements 



