164 



TWENTY-NINTH FRUIT-GROWERS' CONVENTION. 



would simply swing around and when the insect had regained its hold 

 it would then climb upward. Thus an insect would sometimes start 

 time and again to go around an apple and would be brought back to 

 the upper side by slipping as just described, and finally would proceed 

 to enter the apple on the upper side. A rough surface seems to be 

 preferred to a smooth one, and blotches of lime and poison were 

 certainly not avoided by the worms. 



In our breeding-cage experiments which were conducted in a wax 

 cell covered by a thin piece of glass the burrows were invariably made 

 either under the edge of the wax ring, or at the point where the cover 

 glass nearh^ touched the surface of the apple. In this latter case the 

 worm could be observed under the microscope very satisfactorily. It 

 would first make a silken carpet and then spin a series of threads 

 connecting the glass to the apple, making a strong, but an almost invis- 

 ible cell for itself, the silken threads being so delicate as to be seen only 

 with the use of the microscope and the proper illumination. After 

 accomplishing this preliminary work the worm would begin the pro- 

 cess of excavating a hole for itself, the most difficult part of the opera- 

 tion seeming to be the first breaking of the skin, which would often 

 require a great many attempts before the jaws would tear through 

 into the softer tissues beneath. As soon as the first piece is removed 

 from the surface of the apple the worm fastens it to the silken struc- 

 ture which it has erected about itself, and then another bite is pried off 

 and added to the first, and this is repeated until quite a wall of apple 

 chips has been built around the burrow. By this time the worm has 

 made a hole pretty nearly as deep as its body, and finds it necessary 

 to withdraw itself after each bite is obtained. The hole is not dug 

 straight down into the apple, but somewhat obliquely and considerably 

 larger than the diameter of the insect. It is soon, therefore, able to 

 turn itself about within the burrow, and then only pushes its head out 

 far enough to add to the chips already accumulated on the sides, and 

 finally the mass entirely covers over the opening which it has made in 

 the fruit. Up to this time, the worm has worked incessantly and the 

 stomach has received none of the material removed from the apple. 

 Shortly after the completion of the burrow, however, the digestive tract 

 is seen to be well filled with chips of exactly the same character, so 

 far as can be observed, as those that were used in the construction of 

 the covering on the outside. 



It would appear from this observation that under the conditions 

 existing at Watsonville by far the larger percentage of the worms 

 gain entrance to the inside of the apple before the poison can reach 

 them. In sprayed trees it was observed that the majority of the 

 worms died before going deep into the fruit. This is in striking con- 

 trast with the history of the worms in unsprayed trees adjoining. There 



