144 



probably near two hundred. There is no pubHshed account of 

 the occurence of the flat larva in Europe, and it is not probable 

 that it would have remained unnoted had it been found there. 

 In this country the flat group is represented by only fourteen 

 species, and L. ornateUa is the only species of its group as yet 

 made known. All the other species belong to the cylindrical 

 group. Though the species of the flat group are comparatively 

 so much less numerous, the individuals are as numerous as those 

 of the cylindrical group. So far as the mines are concerned, 

 this might be explained by the fact that the mines of the flat 

 group are always on the upper surface and are large, conspicuous 

 blotches, while those of the cylindrical group are smaller, and 

 with the exception of L. tiliaeella Cham, and L. rohiniella Clem, 

 in this country, are always on the under side ; but this will not 

 explain the greater abundance of the moths of the flat group. 

 This is owing, as I believe, simply to the fact that they are more 

 prolific. The larvse of this group are gregarious, while it is a 

 comparatively rare thing to find more than one larva in a mine 

 of the cylindrical group. 



The larval life of a Lithocolletis lasts, in Kentucky, in mid- 

 summer, about three weeks. Many species, however, pass the 

 winter in the larval state, though their development may be 

 hurried by keeping them in a warm room ; then the moths make 

 their appearance irregularly, according to temperature, all 

 through the winter. It is probable that the larval life can not 

 be shortened to a less time than three weeks. Since the larvse 

 cannot be removed from one mine to another, and it is difficult 

 to keep the leaves green and fresh for so long a time, the only 

 way to determine the length of the lai'val life is by observing a 

 multitude of mines in various stages. From such observations, 

 repeatedly made, I find the length of larval life to be about 

 three weeks. In this period the larv« moult eight times, at the 

 eighth moult passing into the pupa state. This seems to be a 

 large number for so short a life-time, but I am convinced that it 

 is correct. I have already alluded to the difficulty of determin- 

 ing this matter accurately as to larvae which are concealed in 

 their mines, but I have observed hundreds of the larvge in various 

 stages of growth, and I find always seven distinct sizes in each 



