Tmf. Frey, and some American Tcueina. 203 



we can, how the Professor ever made this egregious blunder. The in- 

 sects do not even belong to the same group in the genus. But first it 

 must be mentioned that Dr. Clemens long ago announced that there 

 were two forms of larva in this genus : one is the ordinary cylindri- 

 cal form, which is perhaps the most common form, the other is a de- 

 pressed, almost flattened form, with the ventral legs scarcely apparent ; 

 indeed, the cylindrical form seems a much more highly developed ani- 

 mal, internally as well as externally, than the flat form, and if the dif- 

 ferences of the imagos were as great as those of the larvae no ento- 

 mologist would think of classing them in the same genus ; yet, never- 

 theless, an imago derived from a cylindrical larvse will frequently be- 

 long to the same group, and be marked very much like one derived 

 from the flat group. ISio species of LithocoUetis is known to have larvae 

 belonging to both forms. L. Cindnnatiella , Cham., comes nearest to 

 this. It really seevu to have two forms, one the ordinary flat larvae, 

 and the other I have usually found alive in the winter, a much larger 

 larvae, almost cylindrical, but yet depressed and differing much more 

 from the cylindrical larvse than it does from the ordinary 

 flat form. Its mouth parts are those of the flat form, and 

 so are the feet, but more distinct and better developed. Conse- 

 quent on differences of form, are those of life and habit. Thus 

 the cylindrical larvae stands erect and crawls, like any ordinary 

 caterpillar, on its feet, and owing to this and to the form of its head 

 and mouth, its mine must he tentiform, that is, the parenchyma is eaten 

 out between the upper and lower cuticles of the leaf, and one side or 

 the other becomes somewhat drawn, so that the cavity within becomes 

 roomy and tentiform, as I before explained as to the mines of the sugar- 

 tree leaf miners. In two species that we know, the cavity is such that 

 the cocoon of the pupa is suspended in it like a hammock, by a thread 

 from each end. The flat larvae rather wriggles than crawls, and by 

 reason of its form it does not need a tentiform mine ; and by reason of 

 the form of its head and mouth parts, it can not make one. The mine, 

 therefore, is always flat. I have observed, also, that the flat mine and 

 larvae are always on the upper side of the leaf, except in the case of 

 L. ornateUa, and the cylindrical larvae and tentiform mine usually, but 

 by no means always, are found on the under side of the leaf. L. rohin- 

 iella, Clem., and L. tiUiceella, Cham., are standing exceptions to this 

 rule, and I once saw a leaf of the elm with two mines of L. argentino- 

 tdla, Clem., on the under surface, and one on the upper surface, from 

 which I had all these specimens. Mr. Stainton (page 63, of his edition 

 of the Clemens papers) says, he "doubts much whether we have in 

 Europe anything like the second (flat) group of the larva?."' From an 



