130 THE APPLE LEAF HOPPER 



Plants Plants 

 37 Plants to the Row Heads Without ^ "',:,„ 



Heads JviissmK 



Cards (5 rows) 144 19 22 



Check (10 rows) 249 49 72 



Figuring on the basis of 10 rows gives the following comparative table; 



37 Plants to the Row Hesids Without An''i.,cr 



Heads -^^issing 



Cards 288 39 44 



Check 249 49 72 



This shows a gain of 39 heads on the rows where cards were applied, 

 and the conditions were practically equal where plants failed to produce 

 heads, and in the number of dead plants there is a decided difference in 

 favor of the plants with tarred felt cards. 



EXPERIMENT NO. 18— BURYING PUPARIA AT DIFFERENT 



DEPTHS. 



This idea was suggested by the possibility that fall plowing might 

 bury many of the cabbage maggot puparia so deep that the adult flies could 

 not penetrate the soil and emerge the following spring. 



Two series of experiments were made in order to determine whether 

 the puparia could be buried to a depth reached by plowing so that the flies 

 would be unable to emerge. The first series was made by Webster in the 

 insectary during March and April. The puparia were buried in the sand 

 in pots at depths of from one to six inches. Five puparia were placed in 

 each pot. No flies emerged when pots were buried one and two inches 

 deep, and only one fly emerged from each of the remaining four pots. 

 Moisture conditions were rather unequal in the different pots, and it is 

 probable that the pots containing puparia buried at one and two inches were 

 too wet. When examined on Ma}- 16th the puparia in these two pots were 

 badly decayed. 



Puparia were collected from roots of cauliflower in the field and buried 

 at depths of from one to six inches. They were placed in a wooden box 

 set in the ground and covered with netting. This was placed out of doors 

 near the insectary. The box was divided by six tightly fitted partitions, 

 and the puparia buried in damp earth, making the conditions as nearly as 

 possible the same as outside. Ten puparia were buried in each partition, 

 except in the three inch, which contained only nine. The soil become hard- 

 ened through the action of rains, so that it was practicallj- the same as 

 the outside soil. No flies emerged from the puparia buried one inch or six 

 inches. From the puparia buried two inches, three flies emerged; those 

 buried three inches, one fly; four inches, two flies; and five inches, three 

 flies. 



From this it would seem that the flies were not able to penetrate 

 through six inches of soil under conditions as nearly like outside conditions 

 as possible. 



EXPERIMENT NO. 19— VARIETY TESTS. 



Holland Cabbage: Planted 50 Holland cabbage May 17th between rows 

 of cauliflower, .\tthe end of the season cauliflower plants were found slightly 

 infested with cabbage maggots, but no maggots were found on the Holland 



