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36 
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 CoccinellcB , 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. Fie also discover¬ 
ed under some of the scales a little oval, footless maggot,whicli 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. 
Fetch’s statement, and adds that he had often noticed the round 
holes in the scales, which he also attributes 1o 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, I 
happened to uncover one of these insects in the last stage of its 
transformation. Its wings were not yet unfolded, but it ran so 
