50 IMPORTED PARASITES. 



It will be several years before they will reach the abundance 

 at present held by Moncfdontomerus. 



These two insects, Monodontomerus and Calosonia,^ were the 

 only enemies of the gypsy moth which were liberated in 1906 

 in time to attack the gypsy caterpillars that year. A number 

 of other parasites were given their freedom during the late sum- 

 mer or fall, after the caterpillar season was nearly or quite over, 

 and the first opportunity which they had to attack the gypsy 

 or the brown-tail caterpillars was in the year following. Of 

 these parasites, one, Compsilura, has been recovered in the past 

 summer in numbers in every way as large as could be expected, 

 if its rate of dispersion is as rapid as that of Monodontomerus. 

 A greater rapidity of dispersion and multiplication, sustained 

 over a period of years, has not been expected of any of the in- 

 troduced insects. 



WHEN WILL THE PARASITES BECOME EFFECTIVE? 



This question, which has been asked so frequently, has always 

 been avoided, especially since it became apparent that the dis- 

 persion of the parasites was going on at an unexpectedly rapid 

 rate, making their recovery difficult except in the immediate 

 vicinity of the colony and immediately after colonization. It 

 was obviously impossible, under such circumstances, to deter- 

 mine what their actual progress was ; and the only results which 

 were apparent to those in charge of the work were so technical 

 in their nature as to be of little significance to any one not 

 thoroughly familiar with entomology. 



During the past few months considerable data have been accu- 

 mulated, uniformly satisfactory in character, which bears upon 

 the rate of dispersion or of multiplication of certain of the para- 

 sites. It is very insufficient, but if it is reliable, and if the 

 progress of the first among the parasites and predators to be 

 liberated may be taken as a criterion of what is to be expected 

 of the others, it is possible to make a fair estimate of the length 

 of time required for the parasites to become sufficiently abun- 

 dant and so generally distributed as to bring about an effective 

 natural control of the gypsy moth. The different species differ 



^ Cahsoma inquiaitor, another predaoeous beetle, was also liberated in 1906, but in rather 

 email and unsatisfactory numbers. It has not been recovered. 



