1911 ENTOMOLOGICAL SOCIETY. 63 



of the results of this work and the different natural means of control which had 

 been discovered were described.* The chief of these was the ichneumon, Mesoleius 

 aulicus, Grav., which was found emerging from the cocoons about the same time as 

 the adult sawflies were emerging. In the spring of 1908, during which year the 

 defoliation of the larches was very serious, a beginning was made in studying the 

 course of the chief factor in the natural means of control, namely Mesoleius 

 aulictis, and the average number of cocoons parasitized by this insect in 1908 

 (strictly speaking one should say 1907, as 1908 is the year of their emergence from 

 the hibernating larvae,) was six per cent. In the following year, 1909, the per- 

 centage of ichneumons emerging had increased to twelve and fifteen per cent, show- 

 ing that the parasites were increasing in number, though not very rapidly, and there 

 did not appear to be any falling off in the abundance of the sawfly. In 1909, I 

 relinquished charge of the English work on coming to Canada. As this investigation 

 was of considerable interest to me and as I was continuing my study of the insect 

 and its parasites, arrangemenits were made for a shipment of the cocoons collected 

 in the English districts in which the investigations were previously carried on, to 

 be sent to Canada. During the spring of this year the percentage of cocoons para- 

 sitized with M. aulicus was again counted and to my great pleasure and surprise I 

 found that they had increased to over 60%. This was confirmed, in England, by 

 Mr. J. Mangan, who continued the work on my departure; he found 62% parasit- 

 ized. What was originally considered to be of theoretical importance only, is now 

 seen to be of practical importance. We know that in about another year the sawflies 

 will be practically controlled by the parasite in those localities so severely infested 

 previously; where trees had been killed by repeated defoliation and the owners were 

 cutting and contemplating cutting down immature timber to save it. This is now 

 unnecessary and Mr. Mangan informs me that in those localities where the sawfiies 

 were so abundant previously it is almost impossible to find them. The trees which 

 in previous years had all the appearnce of having been burnt, so complete was the de- 

 foliation, this year appeared almost normally green. Other localities, however, were 

 more severely infested, and the Board of Agriculture, I understand, are adopting 

 the recommendation in my paper to which reference has already been made, namely 

 the collection of cocoons from localities where the percentage parasitized is very 

 great and their distribution in localities where the outbreak is first beginning. In 

 this way the practical application of natural means of control is made and we are 

 able to assist nature in gaining this control and to hasten on the control far more 

 rapidly than would be the case if affairs ran their natural course. This acceler- 

 ating of natural eradicative measures will prevent also the loss of trees which occurs 

 in the natural course of events. Several hundreds of the chief parasites Mesoleius 

 aulicus which I reared at Ottawa were liberaited there, and some were sent to Al- 

 gonquin Park. 



A furtlier parasite of N. enchsonii and which appears to be abundant both in 

 Canada and the United States is a small Chalcid, which Packard was the first to 

 figure as Pteromalus nematicida, although he did not describe it. We found this 

 parasite very abundant in some cocoons collected on the Experimental Farm, at 

 Ottawa, in 1909. This year, through the kindness of Mr. Fiske, of the Gipsy Moth 

 Parasite Laboratory, Melrose Highlands, Mass., I was able to secure a further supply 

 of cocoons from Wellesley, Mass., infested with the same parasite, the life-history 

 of which we are now studying, as I believe it is one of the most important natural 

 means of control that we find. It is very easy to get them to oviposit under laba- 



♦These have already been described in my paper, " The Large Larch Sawfly, Nematus 

 erichsonii, Hartig." Journal Board of Agric. (London), Vol. XV., pp. 649-6&0. 1908. 



