41 [ 461 I 



without auy traces of the parasitic Chalcides, and this section of coim- 

 trj^ seemed therefore to furnish a favorable fiekl in which to try the ex- 

 periment of coIonizatit)n. * 



Captain Edward H. Beebe, of Galena, who had been passing the 

 winter in Geneva, and who had taken a lively interest in this investiga- 

 tion, undertook to conduct this interesting- experiment. Early in the 

 spring of 1S71, on his return to Galena, he took a package of twigs, 

 which we had ])rocured from trees known to have been inhabited by the 

 Chalcides, aind under some of the scales upon which it was therefore 

 probable that the larva^ were hibernating. These he tied upon trees in 

 three different orchards, in the town of Galena, which were known to 

 be badly infested by bark-lice. 



When we consider the minute size of these insects, the fully matured 

 fly being only one twenty-fifth of an inch in length, and that the hole 

 in the scale of the bark-louse which reveals the operation^ of the Chal- 

 cis is so minute that it can only be seen hy the aid of a magnifying 

 glass ; and we further take into account that i)robably less than a dozen 

 of these larvaj were transported to the new locality, and that the small 

 number of parasitic flies proceeding fi'om these were let loose in three 

 orchards containing many hundreds of apple trees, we may form some 

 idea of the difficulties of this experiment, and of the uncertainty which 

 would be likelj' to attend any observations made for the purpose of de- 

 termining the presence of the Chalcides. Even if the experiment should 

 prove ultimately successful, it would be very doubtful whether the Chal- 

 cis marks would be sufficiently numerous to be detected at the close of 

 the first year, but after this they would be likely to multiply in a rap- 

 idly increasing ratio. 



About the last of May, 1872, that is, after the intervention of one 

 year from the time of commencing this experiment, Caf)t. Beebe exam- 

 ined some of the trees to which the Chalcis twigs had been attached, 

 and after a careful search thought that he had discovered a few traces 

 of the operations of the Chalcides, and sent half a dozen of the twigs 

 bearing these marks to me for inspection. We may here state for the 

 information of those who have not seen our former articles upon this 

 subject, that the scales of the bark-louse are found to be damaged by 

 two very different kinds of insects, namely, the larvie of the CoccinelUd* 

 or lady-bugs, which gnaw ragged holes through the scales for the pur- 

 pose of obtaining and devouring the lice beneath, and the minute para- 

 sitic Chalcis flies, of which we are speaking, which cut i^erfectly clean 

 and round holes, for the purpose of escaping from the cell, in which, 

 after devouring the rightful occujDant, they have undergone their trans- 

 formations. Vpon the selected twigs were found some marks of the 

 Coccinelhdie, and also a few holes, about one to each twig, which were 

 Vol. IV— 49 



