500 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1920. 



much silk here that the central part finally shows as an opaque 

 disk. The shelter completed, the caterpillar coils up within and 

 waits for the molting process to proceed. 



To the naked eye the molting cocoons form tiny glistening spots 

 on the leaves (pi. 2, G, d), usually near the margin or at the tip, the 

 largest scarcely the twelfth of an inch (2 mm.) in diameter. After 

 two or three days the molting is completed and the caterpillar 

 emerges through a slit cut in one side of the roof, leaving the old skin 

 and the head capsule behind on the floor. 



From now on the Bucculatrix caterpillar is a free creature, feed- 

 ing in the open on the upper surfaces of the leaves where it eats out 

 little patches of the epidermis, giving the leaf a spotted appearance 

 (pi. 2, H). But after several days of undisturbed feeding it must 

 shed its skin again and for this purpose builds a second molting 

 cocoon. These cocoons become abundant on the leaves during mid- 

 summer. They are larger than those of the first molt, the largest 

 being twice their width, about one-sixth of an inch (4 mm.) in 

 diameter. They may be spun over any little depression of the leaf, 

 most of them on the upper surface but some on the lower, though, as 

 before, the apex of the leaf where the usual twist makes a small 

 hollow, is a favorite site. The caterpillar weaves the whole struc- 

 ture, enters it and. closes the door in about an hour's time. 



After the second molt the caterpillar appears in the last stage of 

 its larval growth and spends another period of feeding on the leaves 

 (pi. 2, J, <?), many of which on infested trees now become spotted 

 all around their edges Avith little red-brown areas where the upper 

 epidermis has been eaten off and the exposed lower skin has died. 

 In the network of its veinlets a leaf presents to the caterpillar hun- 

 dreds of little pans of food, all of which should be of equal quality ; 

 but the Bucculatrix caterpillar, after having emptied a few pans 

 at one place, moves over to a neighboring spot and there cleans out 

 a few more. Either its appetite is quickly sated for the moment or 

 it always thinks perhaps the fare is fresher farther on, for it keeps 

 up this wandering style of feeding, leaving small groups of empty' 

 dishes all over the leaf. After a while it seeks a new leaf, usually 

 dropping down to one below from the end of a thread. Thus each 

 caterpillar damages a single leaf over a wide area and injures many 

 more leaves than necessary for its support. It is not good form 

 with Bucculatrix to eat the bottom out of its dish, though sometimes 

 a careless caterpillar makes an accidental puncture with the points of 

 its jaws,'but the exposed lower epidermis often cracks as it drys, and 

 leaves that have been badly injured frequently turn brown all over 

 and curl up. Thus, while Bucculatrix usually only disfigures the 

 leaves, it may, when exceptionally abundant, do serious damage to an 

 orchard by its widespread feeding on the foliage. 



