51 



fined a great many worms for days at a time, not a healthy pupa of* 

 rapes was formed. 



Neither of these parasites nor any other affected the Plusia in the 

 least. 



About August 20 the Plusias began to appear in greater numbers, 

 not formidable as yet, but so numerous that I began to collect them in 

 separate cages for experiment. From this time on until the 1st of 

 October this insect multiplied at an astonishing rate. About the mid- 

 dle of September a late bed of cabbage, of perhaps a little more than 

 one acre, Avhich had almost escaped rapce, was found to be literally alive 

 with these larvae, from ten to forty or fifty beiug found on a single 

 plant. They destroyed it very rapidly, until the gardener put a man 

 under my direction to kill them, which was done very successfully. 

 The moth was not observed to move about at all during daytime, but 

 was frequently found hidden among the leaves of the plant. When 

 disturbed it flew rapidly in a zigzag manner and soon alighted. 



It deposits its eggs irregularly over the lower side of the leaf, vary- 

 ing from a few in number to twelve or twenty. This habit makes it a 

 worse enemy, in my estimation, than rapce, as they deposit their eggs 

 singly, and never in my observations do they happen to get so many 

 on one plant as brassicce does. The latter, from my observations, is 

 much the more prolific, and is also more hardy. 



THE CORN APHIS. 



(Aphis maidis.) 



The only injury I have ever known to be done by this insect occurred 

 this year, about 6 miles northeast of this city. A gentleman planted 

 his corn earl}" in May. The weather was quite favorable, and it came 

 up promptly and looked well for a few days, and then began to turn 

 yellow and wither awa}\ On examining he found what he rightly 

 called a "small louse" in great abundance, and associated with it a 

 great many small ants. He could not conclude that the louse was the 

 cause of injury, so laid it to the ants. The injury became so great in a 

 few days that he concluded to plant the field all over again, which he 

 did with a two-horse check-row planter. This planting was taken the 

 same as the first, and the field again planted over. This last planting 

 was not much injured, and with the remnants of first two plantings 

 made quite a crop. On the 11th of July, being in the neighborhood, 

 my attention was called to the field. I still found the Aphis present 

 in considerable numbers, but the corn was doing fairly well. A Large 

 number of insects were examined, yet none but apterous forms were 

 observed. The first field is black- loam bottom-land, extending partly up 

 on upland, lying beside a creek of considerable size; it is well drained, 

 and the soil is loose and friable. 



