80 



of the leaf, it is evident that each egg is placed somewhat more ver- 

 tically than the preceding one. But as there are never more than five 

 eggs in a single egg mass, the last of these is still placed obliquely, 

 and the egg mass when viewed from the side slopes very gradually in 

 the direction toward the first egg while it ends more abruptly at the 

 last one. Owing to the glutinous and excremental coverings the indi- 

 vidual eggs can not be distinguished from above, but on the sides and 

 from beneath, where the glutinous covering is veiy thin or absent, they 

 may be plainly distinguished. The glutinous substance appears to 

 possess some caustic properties, for the place of an egg mass can always 

 be seen on the upper side of the leaf as a small brown spot. It hardens 

 very rapidly, and becomes so tough and firmly adherent to the eggs 

 that these can not be taken out from a mass without destroying them. 

 The duration of the egg state appears to be very variable, most of 

 those which were gathered (in Jul} T ) when apparently quite freshly 

 laid hatching in from six to eight days, while others of the same 

 batch hatched nearly a week later, but in every instance all the eggs 

 of one egg mass hatch nearly at the same time, or at least within the 

 space of a few hours, the first-laid egg usually hatching first. 



Tin larva and its marl-. — The young larvae invariably break through 

 the egg shell on the underside of the egg mass and at once begin to 

 gnaw through the epidermis of the leaf without leaving the protecting 

 egg mass. Then they proceed to eat out the inside of the leaf, leaving 

 only the epidermis of both sides of the leaf intact, thus forming what 

 in scientific terminology is known as a tentiform mine. There is only 

 one entrance to the mine, that made by the first-hatched larva, the other 

 larva' entering the inside of the leaf by the same hole. Thus from 

 three to five young larvae are usually found within the same mine, 

 which rapidly grows through their united efforts. In fact, within a 

 few hours four young larva 1 had hollowed out about one-fourth of a 

 large leaf, and it is evident that a single leaf is not sufficient to nourish 

 the larva? during their life duration. Moreover, the larva? have the 

 habit of hollowing out not more than one-half or at most two-thirds 

 of a leaf. Thus in from two to four da}^s after hatching (the time 

 varying according to the state of the weather, the number of the 

 larvae, and the size of the leaf) the larva? leave their original mine, 

 wander off along the leaf stems, often to a considerable distance and 

 to another twig, and form new mines, but this time each larva lives 

 b} T itself. There are never two separate mines on one and the same 

 leaf, and only once were two nearly full-grown larva? found in the 

 same mine. In captivity this process of migration was repeated as 

 often as the leaves began to wilt, but we did not succeed in ascertain- 

 ing the number of these changes in nature, owing to the difficulty in 

 following the individual larva? in their migrations, which appear to 

 take place at night. This much has been ascertained, that at least 



