342 DAVENPORT ACADEMV OF NATURAL SCIENCES. 



Leidy for a copy of his report already referred to, and for a number of 

 specimens of innumerabllis from Philadelphia ; to Dr. J. A. Lintner for 

 a copy of Fitch's article on acericorticis ; to Mr. J. V. Walton of Musca- 

 tine, for a piece of grape vine infested with innumerabilis ; to Mr. H. F. 

 Atwood of Chicago, for valuable information regarding the preparation 

 of these insects for the microscope ; and to our members, Mr. A. S. Tif- 

 fany, Mr. W. H. Pratt, Dr. E. H. Ilazen. Dr. C. C. Parry, Mr. John 

 Hume, Mr. Simpson, Mr. John Temple, and many others for specimens 

 and information, and assistance of various kinds. To Miss Emily A. 

 Smith of Peoria, Illinois, who has made a contemporaneous study of this 

 species, I am specially indebted Cor the frequent communication of her 

 observations and discoveries, which for the most part have served to 

 confirm my own, In some cases to anticipate them, and only in few es- 

 sential particulars appear to differ from mine. To the subjects of habits, 

 parasites and remedies she has given more attention than I have done. 



In making this study I have used a McAllister's Physician's Microscope 

 stand, with H, I and 1-5 objectives by Wm. Wales, and magnifying from 

 5 to 450 diameters. The stand is small, but I found it very convenient 

 for this kind of work. The objectives were of the cheapest, low angled 

 form, but worked very satisfactorily, except that in some cases a greater 

 amplification would have been desirable. 



. In pursuing this study I have prepared a series of more than 200 mi- 

 croscopic slides, illustrating every stage of the developmentof this insect, 

 and containing from one to more than 100 specimens on each. These have 

 been prepared by the following methods ; 1st, mounted directly in pure 

 glycerine; 2d, placed first in alcohol, then in glycerine and mounted in 

 glycerine ; 3d, placed first in oil of cloves, or in turpentine, and mounted 

 in Canada balsam ; 4th, placed first in solution of potash, then in water, 

 then in alcohol, then in turpentine, and mounted in Canada balsam ; .5th, 

 mounted directly in solution of »alycilic acid; 6th, in solution of acetic 

 acid ; 7th, in solution of white of hen's egg, and 8tl), in pure water. Each 

 of these methods has its special advantages and neither is to be relied 

 upon implicitly. My studies have been made by a comparison of all 

 these and of great numbers of living individuals, the whole number ex- 

 amined carefully amounts to several thousand examples, with an infinite 

 number examined superficially. For all observations recorded in this 

 paper I am alone responsible, except where it is expressly stated other- 

 wise. 



A large number of drawings were made witli and without the aid of 

 a camera lucida, of which only a selection is given on the plates. The 

 plates are my first attempts at etching on steel and naturally are quite 

 imperfect, as it is difficult without experience to produce just the desired 

 effect, but the outlines are, I think, very nearly correct. The figures 

 have all been carefully drawn to scale, and the amount of amplification 

 annexed in every case. I regret that I was not more uniform in the .use 

 of reference letters on the plates, but the importance of this matter did 

 not fully impress me until after the etching had been completed. 



