28 DR. BRACKENRIDGE CLEMENS' LETTERS. 



within the mine, that are extended as the mine increases in 

 length, forming a tube, transparent above and below, which 

 leads to an opaque one alongside of the mid-rib of the leaf.* ■ 

 When the larva is alarmed or disturbed it retreats along 

 this way and conceals itself under the opaque portion along 

 the mid-rib. It quits the leaf to transform, and weaves a 

 little ovoid cocoon. 



I sent you a Lithocolletis which mines this leaf also, and 

 there is still another species in it, which had not become 

 pupae at that time, whose cocoon is a little ovoid mass formed 

 of "frass." 



I have found other tube-forming larvns, that construct 

 their tubes on the outside of leaves. One of these is very 

 singular, its tube being two or three inches in length, and 

 covered at the large extremity by a Aveb of silk, under which 

 the larva feeds. I have two cocoons of this larva which 

 I hope will produce imagos. It is rather rare in this locality, 

 but two years ago I found it very abundant in the oaks of 

 Minnesota near Saint Paul. I did not succeed in getting 

 pupas at that time, and I think Pennsylvania is probably its 

 southern limit. 



I am much obliged for the kind invitation you have given 

 me to consult you, whenever I find myself in difficulty. 

 There are a great many questions I should like to ask, but 

 I know how valuable is your time, and feel sure much of it is 

 devoted to the incipient Entomologists of your own country. 

 Then, too, I have been taught, from my youth, in the words 

 of the homely adage, that " those who help themselves, God 

 helps." 



Is there a genus in the family ElachistidcB, the larva of 

 which form their cocoons in a. thin open net-work, so that the 

 pupa is visible? I found larvas which made cocoons of this 

 kind feeding on the drupes of the fruit-heads of sumach. 



I am quite sure I have found a new genus in Lyonctidcc. 

 I am acquainted, however, only with the imago. Are there 



* Nothing at all analogous to this is known amongst the mining Lepi- 

 dopterous larva? of Europe. II. T. S. 



