44 THE APPLE LEAF HOPPER 



the original stem mother, rather than descendants of a migrant form 

 from the South ?" 



In other words, it may be that in place of calling this insect the 

 Southern (Irain Aphis, we shall have to make use of the term already 

 applied to it by numerous scientists, namely, the "Spring Grain Aphis," 

 and regard it as a permanent resident in Minnesota. We see, how- 

 ever, no reason to change our views as to its comparative harmless- 

 ness in this state under our normal climatic conditions. 



This insect, in the past two years, has been found pretty gen- 

 erally scattered over the wheat growing portions of the state. 



In the insectary several series of Toxoptera were carried through 

 from the egg, the experiments showing how prolific the "Green Bug" 

 (other plant lice have this characteristic strikingly developed) may 

 be. The record of three of these series arc here given. The eggs 

 used were those found in the river gorge April 7th, above referred to. 

 They hatched on April 14th. From these we took one, a "stem 

 mother" of course, and taking the first young produced in each gen- 

 eration, obtained the following results. By "first generation" we 

 mean this stem mother. Her young would be the second generation, 

 and we took the first individual produced from them to represent 

 the third generation, and so on. In other words, in the following table 

 the dates indicate the date of birth (of hatching in the case of the 

 stem mother) of the first of each generation, and in the column to the 

 right of this the number of young produced bv this individual : 

 SERIES D— 

 1st Generation (stem mother) April 14 — 41 young. Experiment No. 95 

 2nd '• '■ 24—73 " '■ " 102 



3r(l " May 5—67 " " " 112 



4th " •• 16—69 " " " 129 



5th •• •• 25—76 '• " " 137 



6th •• June 4— 6 " " " 156 



7th •• •■ 15—36 " " " 174 



8th ■■ ... 24—73 '• '■ " 192 



9th • July 2—70 " " " 216 



10th •• " 10—56 " " " 230 



ilth •• '• 17—57 " " " 241 



12th •• " 24—92 " " " 252 



13th •• " 29—78 " •' " 268 



14th •• Aug. 4 — 52 " " " 299 



15th •• •• 12—85 '■ " " 324 



16th " •' 21—29 ■• •' " 346 



17th " " 25—96 •• " " 360 



Taking these seventeen generations, we find that the sum of the 

 young produced in each by the first individual born amounts to 959. 

 or an average of 57 for every generation. 



