36 0TSTEK-8HELL BARK-LOUSE. 



ful by the fact, that in some localities, at least, where the scales 

 containing these discolored eggs are not uncommon, the Acari are 

 comparatively rare. Of eighty-one scales just examined ( Sept. 26), 

 containing these shriveled and discolored eggs, in only four were 

 Acari seen. It is possible, however, that they may have left them 

 after having extracted their contents. 



But, besides the ragged holes above mentioned as the work of 

 the CocdnelloB^ a much larger number of scales are found through 

 which has been bored perfectly smooth and round, or slightly oval, 

 holes, which we know from analogy must have given exit to some 

 parasitic fly. These holes have been particularly mentioned by 

 several of our entomological writers, and must have been seen by 

 all who have made a special study of the Apple-tree Bark-louse. 



So long ago as the year 1855, Dr. Fitch, in his first Report upon 

 the Noxious Insects of New York, gave a history of this Bark-louse, 

 so far as it was then known, and mentions the frequent occurrence 

 of these round holes in the scales at that time. He also discover- 

 ed under some of the scales a little oval, footless maggot, which he 

 conjectured might be the larva of some hymenopterous parasite, 

 which, in its exit, made the holes in question. 



In 1867, Mr. "Walsh, in his history of the Bark-louse, in his first 

 annual Report upon the Noxious Insects of Illinois, refers to Dr. 

 Fitch's statement, and adds that he had often noticed the round 

 holes in the scales, which he also attributes lo the exit of a para- 

 sitic insect belonging to the Chalcis or Proctotrupes family. But 

 he says he had never met with the larva described by Dr. Fitch. 



In the course of a series of observations upon the Apple-tree 

 Bark-louse, during the past season, it has been my good fortune to 

 trace the history of this interesting little insect, which, if it has 

 ever been seen before, has not been identified, and whose very ex- 

 istence has been only a matter of inference from the visible marks 

 of its beneficent operations. 



In the early part of the season, whilst examining the lice upon 

 an apple tree, I noticed two or three little yellow Chalcides running 

 along the infested twigs, which I conjectured might be the para- 

 sites of the Bark-louse, but had no proof that this was the case. 

 But about the first of August, upon raising one of the scales, 1 

 happened to uncover one of these insects in the last stage of its 

 transformation. Its wings were not yet unfolded, but it ran so 



