Investigation of Scarring of Fruit by Apple Redbugs 191 



is no longer able to reach the core tissue. Redbug punctures that pene- 

 trate the core develop a very different type of scar from those made at a 

 later period. When the core tissue is punctured, the fleshy part of the 

 apple grows up around the point of puncture, leaving a deep pit where the 

 injury occurred; this is shown in figure 23 (page 188), a photograph taken 

 four weeks after the punctures were made. Such apples invariably develop 

 deep sunken pits, as shown in the mature Northern Spy apple (fig. 24). 

 Of the varieties observed by the writer, the Northern Spy is the slowest in 

 developing size in the fruit, and thus a higher proportion of deeply pitted 

 apples are found in that variety. The Rhode Island Greening and Baldwin 

 apples develop more rapidly following the set of the fruit, and hence 

 the time is more limited during 

 which the insects may reach the 

 core and produce the deep wounds ; 

 this results in a smaller proportion 

 of deeply pitted apples and more 

 of the russet-scar type. 



The irregular russet scars that 

 have been so little understood are 

 developed from punctures made 

 just after the apple has become too 

 large for the insect to reach the 

 core with its beak and while the 

 fruit is growing very rapidly. In 

 figure 27 Rhode Island Greening 

 fruits are shown with nymph and 

 adult redbugs, at a time when the 

 core may no longer be reached 

 (June 18) but when the feeding punctures produce ultimately the peculiar 

 russet scars shown in figures 26 and 30. These young apples (fig. 27) show 

 injuries produced by feeding punctures made on June 10 and 11. The 

 smaller apple shows in two or three places that the core was penetrated 

 when the bug inserted its proboscis, while the larger one had passed that 

 stage before the injury was made. When the fruit is first punctured the 

 sap runs out freely, this being followed by the development of a thick 

 gelatinous covering to the wound, the edges of which turn white after a 

 few hours. In two or three days the wound becomes rusty brown, and if 

 the apple is growing rapidly the skin splits and thus enlarges the wound. 

 It is the late injuries made when the apple is growing most rapidly that 

 spread into the broad, shallow russet scars. In many cases the apple 

 recovers so comi^letely that no depressions result and only the broad, 

 irregular russet scars are seen (figs. 26, 30, 36). 



301 



Fig. 27. YOUNG rhode island greening 



FRUITS WITH NYMPH AND ADULT BUGS 

 (JUNE 18), SHOWING THE PUNCTURES MADE 

 ONE WEEK BEFORE 



