260 TRANSACTIONS OF THE NORTHERN 



stitute proceedings against them on this account, until they shall have 

 had time to cl^an out the bark-lice. 



I have been in the way of receiving, every year that I have held my 

 present ofifice, packages of apple-twigs from different parts of the coun- 

 try, and amongst others from northern Illinois and the southern part of 

 Wisconsin, and it is evident from these specimens, that the natural ene- 

 mies of the bark-louse are not operating here so extensively as in the 

 more southern latitudes. Many abortive scales are found even here, 

 but also many scales full of sound eggs, so that if the process of ex- 

 termination has commenced here it is evident that it is progressing 

 much more slowly than we could desire. 



But the interesting point to which I wish especially to call your at- 

 tention, and to which what I have thus far said is only the prelude, is that 

 upon the infested twigs received from these more northern sections, I 

 have not been able to find any trace of the work of the parasitic chal- 

 cis fly, and the important question, therefore, arose whether these friend- 

 ly insects might not be transported to these parts, and thus an opportu- 

 nity be afforded for them to extend the range of their beneficent opera- 

 tions. But the idea of transporting and colonizing these minute flies, 

 so small, indeed, that they can scarcely be seen by the naked eye, with 

 the expectation of being able to determine by any subsequent observa- 

 tions whether the experiment succeeded or not, appeared, at first sight, 

 to be extremely impracticable. Fortunately, however, for the experi- 

 ment, it was found that this little parasite passes the winter in the larva, 

 or grub state, under the scale of the bark-louse, after having devoured 

 its legitimate occupant. These grubs pass the winter, as a matter of 

 course, in a torpid state, and therefore require no food until the warmth 

 of returning spring restore them to activity. If, therefore, twigs could 

 be taken from trees where this insect was known to have been operating, 

 and taken in sufficient number to ensure a certain proportion of the 

 parasite larvae, and transported during the winter, or very early in the 

 spring, to the desired locality, and be there tied in little bundles to the 

 branches of trees infested by bark-lice, it would seem that the conditions 

 essential to a successful result would be fulfilled. 



This experiment has been actually performed. With the co-opera- 

 tion of my friend, Capt. Ed. H. Beebe, who took a lively interest in this 

 matter, several dozens of twigs were taken from apple trees in my own 

 neighborhood, where this friendly parasite was known to abound, and 

 carried to his place of residence in the northern extremity of the State, 

 and there tied in small bundles to a number of trees badly infested by 

 bark-lice, and where no trace of the chalcis flies could be found. The 

 only way in which it could be determined whether the experiment suc- 

 ceeded, was by dete(;ting at the end of the season, or at some subse- 

 quent time, the presence of the minute round holes in the scales of the 

 bark-lice, which are the infallible indices of the operations of the chal- 

 cididae. When it is considered that these holes are so minute that the 

 search for them has to be made by the aid of a magnifying glass, and 



