70 
Journal of Agricultural Research 
Vol. I, No. r 
in making another incision in the leaf, where she repeats the feeding 
operation. When several females are confined on one plant the under¬ 
side of the leaves soon becomes pitted with these feeding punctures made 
with the ovipositor. Only a small percentage of the punctures contain 
eggs, as the main function of the punctures seems to be to furnish food 
for the adults. The larval mine always commences at this little hole 
or pit. 
The females in confinement readily feed on sugar water, and, no doubt, 
nectar furnishes a part of their food, although no field observations 
prove this. 
The egg period lasts from three to eight days, varying with the seasons 
of the year, but the average period of incubation can be considered as 
four days. 
HABITS OF LARVA AND LENGTH OF LARVAL PERIOD 
The larva (fig. 5) commences feeding immediately after hatching and 
starts mining through the tissues just beneath the upper surface. The 
mine at first is very small and threadlike, 
gradually widening with the growth of the 
larva. Often the miner encircles the entire 
leaf at first and then works into the uneaten 
center, and frequently the mine crosses like 
a figure 8. (See PI. V, fig. 3.) If the leaf is 
small, the entire cellular tissue may be con¬ 
sumed, leaving only the epidermis; in such 
cases the larvae have been observed to enter the leaf petioles and burrow 
a short way downward in an effort to secure enough food to bring 
them to maturity. The larva is not able to enter a fresh leaf in search 
of food, but perishes when the food supply in one leaf is insufficient to 
bring it to maturity. 
The larva is provided with an oral appendage, or rasping organ (fig. 7), 
with which it breaks down the cellular tissue and conveys it to the mouth. 
This feeding “rake” is swung rapidly from side to side, twice a second or 
oftener, while the body moves in an arc as far as can be easily reached, 
when it is quickly brought back to the other end of the “swath” and 
the body moved up a minute distance to reach new cells. The larva 
continues thus feeding incessantly within its mine from the time of 
incubation until maturity. Mr. C. N. Ainslie observed that feeding took 
place at night as well as by day and that strong transmitted light thrown 
upon the larva had no effect upon it. It is indifferent to all external 
happenings, and the epidermis of the leaf may be stripped from the back 
of the feeding larva without disturbing it, provided the head is not 
uncovered. When the leaf epidermis is removed from the head, feeding 
ceases, and the larva can not be induced to resume it. 
Fig. 7.—Mouth armature of larva of 
the serpentine leaf-miner, greatly 
enlarged. (Original.) 
