THE CODLING MOTH IN THE YAKIMA VALLEY. 



71 



were placed on the terminal twigs of a small apple tree, only two 

 developed to half their normal size before they died. 



Before attacking the fruit, the larva will crawl about for several 

 minutes seeking a suitable place to enter. It prefers the calyx cup, 

 stem cavity, or an injury to the skin, as these places afford pro- 

 tection and ease of entrance. When beginning to feed, the larva 

 removes the pubescence on the surface of the apple and cuts into 

 the skin, using its mandibles with a circular motion of the head 

 similar to the action of an auger. The greater part of the skin 

 which is cut away is piled beside the hole, though a little is eaten. 

 Larvae entering apples dipped in a red stain showed the stained 

 particles very clearly in their digestive systems soon after feeding 

 began. When a hole the size of the head is cut through the skin, 



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Fig. 35. — Time of hatching of codling moth larvae, Yakima, Wash. 



the larva excavates a cell large enough to contain its body, and 

 enters, at the same time pulling over the entrance of the burrow 

 the frass which it has laid aside and held in place with silk. This 

 process requires about H hours. 



PERCENTAGE OF TRANSFORMING AND WINTERING LARV.E. 



In Table 60, it is shown that 84.97 per cent of the first brood of 

 larvae transformed the same season in 1919, 76.80 per cent in 1920, 

 and 82.78 per cent in 1921. In both 1919 and 1921, 6 larvae of the 

 second brood transformed the same year, being 1.42 per cent and 

 1.02 per cent, respectively, of the total larvae, while in 1920 only 

 one second-brood larva, 0.21 per cent of the total, transformed. 

 In 1919, 15.03 per cent of the first brood of larvae did not transform 

 until the following spring, in 1920 the percentage was 23.20, and in 

 1921 it was 17.22. Practically all of the second brood of larvae pass 

 the winter in cocoons, the percentages being 98.58 in 1919, 99.79 

 in 1920, and 98.98 in 1921. 



