53 



covers, but a few were observed in which the larvae had evidentty 

 emerged through the lower surface of the egg next to the apple or 

 leaf. 



The young caterpillar is about one-fifteenth of an inch in length and 

 is of a semitransparent color. Later dark spots appear around the 

 hairs. 



The young larva, after piercing the apple, makes a shallow mine just 

 under the skin. Those mines can be easily recognized by the lighter 

 color and by the excrement which is cast out. The larvae which enter 

 by the calyx also take their first few meals at the surface inside the 

 calyx. 



By counting infested apples on unsprayed trees 1 found that about 

 60 per cent of the larvae of the first brood enter at the calyx end. In 

 the later broods but few enter the catyx end. Many enter the apple 

 at the stem end. The greater proportion, probably from 60 to 90 per 

 cent, enter at any part of the apple. A favorite place of entrance is 

 at the point where two apples touch. 



At the end of four or five days the larva commences to tunnel toward 

 the central portion of the fruit. Arriving at the center, it commences 

 irregular excavations, which are filled with excrement, the pellets of 

 which are bound together by silken threads. Surrounded by abun- 

 dance of food, the insect grows rapidly, casting its skin many times. 

 1 have found many burrows, sometimes as large in diameter as a full- 

 grown larva, in which no larva could be found; therefore, I believe 

 that sometimes a larva feeds upon more than one fruit. In all cases 

 where fruits touch they are both injured. 



While one larva usually feeds upon but one apple, one apple may 

 be eaten by mam^ larvae. A large apple was found with thirteen worm- 

 holes in it, both entrance and exit, and three larvae, of various sizes, 

 were feeding inside. It is a very common occurrence to find from 

 four to seven holes in an apple. These different holes are usually 

 made by insects of different broods. In a badly infested orchard the 

 earlier apples rarely had but one insect in each, A larval stage of 

 from ten to fourteen days, as given by Professor Card, is, I think, 

 nearly correct for Idaho. 



On summer apples and most fall apples the effect of the insect is to 

 cause the fruit to ripen prematurely. In the winter varieties, such as 

 Winesap, there is no such ripening. In all cases the fruit is rendered 

 unfit for use. When full grown the larva eats its way to the surface of 

 the apple. The burrow is kept closed by f rass, or sometimes an adjacent 

 leaf is fastened over the hole with silk. Having eaten as much as it 

 desires, the larva pushes out the plug or removes the leaf and leaves 

 the fruit. In warm weather the worms, for the greater part, leave 

 the apples in the early evening or night; but in colder weather, in the 

 fall, they emerge during the heat of the day. If the fruit has fallen, 



