150 [March 



four days before pupation, the larva begins to enlarge the linear mine into 

 a blotch. This enlargement takes place most often over the course of the 

 old linear mine, the latter half of which furnishes the basis of the Lloteh, 

 and hence leaves within it a blackish frass-line. The edges of the blotch 

 are irregular ; in the mine of Plantanella the blotch is circular, or nearly 

 so, and the early portion of the mine is filled with frass, while the blotch 

 is formed by dilating the linear tract, after it becomes five or six lines long. 



The larva, when young, is transparent; color, white, tinged with green- 

 ish, with the thoracic segments swollen, giving it a fusiform appearance. 

 Subsequently it becomes of a pale green color, retaining, however, the 

 swollen thoracic rings. 



In order to insure success in rearing these minute larvae, one must be 

 careful that an excess of moisture does not condense on the sides of the 

 vessels in which the leaves containing them are kept. When the larvce 

 are full fed they abandon their mines in order to weave their cocoons, and 

 if there is much moisture on the sides of the vessel, the larvas will be 

 drowned in it as they endeavor to ascend its sides. When this happens, 

 or when the larvae are disabled by a few hours' submersion in this moist- 

 ure, the observer is not only discouraged, but his care and attention are lost. 



This accident has happened to me very often. In order to avoid it, I 

 have found that if the layer of moist sand is covered with a layer of damp 

 earth an inch or two thick, and packed rather firmly, that the moisture 

 does not collect on the sides of the vessel to such a deuree as to endani-er 

 the lives of the larvae. Indeed its accumulation may be prevented en- 

 tirely, provided the sand is not too wet. The earth should not be wetted, 

 and its degree of dampness should be that which is natural to the soil in 

 summer. If the cover of the breeding-vessel fits accurately, the leaves 

 may be laid simply on the surface of the earth, and they will keep fresh 

 for quite a long time. 



The cocoonets are not as easily detected by the eye, however, on the 

 brown earth, as they are on the surface of white sand. But if the surface 

 of the earth is smoothed with the fingers, so as to leave no fissui'es or 

 cracks in it, the larvae will nearly always weave on the sides of the glass 

 where they meet the surface of the earth. 



The Sycamore miners often weave their cocoonets within their mines, 

 when the air within the vessel is too humid. Previously to weaving they 

 carefully cut the epidermis, some distance on each side of the point at 

 which the cocoonet is to be placed, and thus secure their exit as imagos. 

 According to my observation, this vievcr takes place in nature. And yet, 

 great numbers of the larvae that mine leaves overhanging a stream of water 



