1920] 



Peterson: Hatching of Aphid Eggs 



399 



and they are named in order from south to north. Table 5 

 shows the percentage of hatch and the percentage of eggs with 

 split outer coats on the respective dates. Eggs collected from 

 the southern point, Bridgeton, showed a development decidedly 

 in advance of the eggs collected from the northern point, Cran- 

 bury, in all of the collections, while eggs collected from Glass- 

 boro and Riverton were intermediate in their stage of develop- 

 ment. It is of interest to note that the stage of development in 

 collections from the last named places were approximately the 



TABLE V. 



Influence of the geographical position (temperature) on the development of the 

 eggs of A. avencB. The percentage of eggs with a split outer shell and the 

 percentage hatched in collections made on March 6, 14, 20 and 24, 1919, from 

 four orchards (See Map) in the southern half of New Jersey. 



h = Hatched eggs. 



same. One would expect collections from Riverton to show a 

 slower stage of development. Probably the location of the 

 orchard has something to do with this. The orchard at Glass- 

 boro is approximately 100 ft. higher than the orchard at Riverton ; 

 furthermore the orchard at Riverton is within one mile of the 

 Delaware river and the river at this point is subject to tide. 



Low temperature may kill a small percentage of eggs. The 

 dormant season of 1917-1918 was exceptionally cold, while the 

 winter of 1918-1919 was mild and the temperature never went 

 below 0° F. Eggs of A. avence brought into the laboratory 

 during the last week in February of 1918 and placed in 

 moist chambers (75-90 per cent moisture; room temperature 

 70° F.) showed 43-47 per cent hatch, while a similar experiment 

 in 1919 showed 60-66 per cent hatch. This difference in 



