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in the flat group, are necessary to bring these larvge up to the 

 level of the cylindrical group in its sixth and subsequent stages ; 

 except that the legs of the flat group are never so well developed 

 as they are in the cylindrical group after the fifth, and in L. 

 ornatella after the seventh moult. With this exception, the 

 larvae of all the three groups have reached the same level at 

 the end of the eighth stage. 



I am not positive as to the length of any one stage of larval 

 life except the last (eighth), and of that only in the flat and 

 ornatella groups. In these it lasts between two and three days 

 in the summer, but the fall broods pass the winter in this stage. 

 The moult by which the larva passes into the pupa state is dif- 

 ferent from the previous larval moults. The cast skins of the 

 very young larvse are usually lost in the frass in the mine ; this 

 sometimes happens with the older skins, and I have opened 

 mines of larvse in their penultimate stages, when only a single 

 skin could be found. Usually, however, three or four may be 

 found. In moulting, the head is first loosened completely, and 

 retracted out of its skin, tlie suture between the head and next 

 segment opens on the under side, and the opening extends back 

 along the sides of the next two segments, upon the upper surface 

 of which the head is thrown back ; the larva in its new skin 

 wriggles out at the opening, and very frequently the head is 

 entirely torn off". The skin thus cast is thick and hard, and 

 that cast at the seventh moult frequently remains almost entire. 

 But the skin cast at the eighth moult is thin and delicate, and 

 is usually torn into shreds, which are pushed off to one side in 

 the cocoon, forming a little heap. As this moult takes place in 

 the cocoon, it of course can only be observed by opening the 

 latter, which usually injures the pupa or stops the moulting 

 process. In a specimen of L. ornatella thus opened, I found 

 •some shreds of the skin pushed back to the apex of the abdomen, 

 others adhering to parts of the body, and the skin entirely or 

 partly removed from some of the feet, and uninjured on others. 

 It had the appearance of a pupa which was freeing itself from 

 its larval skin by wriggling about against the sides of its cocoon. 

 In the latter part of its last stage the cylindrical larva becomes 

 wliite, having previously passed from the white of its earHest 



