Oct. 10,1913 
Serpentine Leaf-Miner 
71 
The larval period covers from 3 to 12 days; during the summer months 
it is passed in 4 or 5 days, the time increasing as the days get cooler. 
Many individuals are killed by the autumn frosts while they are yet 
partially grown. They will, however, continue feeding under remarkably 
low temperature conditions in an effort to survive; Mr. Wildermuth 
reared larvae from the time of hatching till they were full grown in 
from 10 to 12 days under a mean daily temperature of 46.8° F., and 
where upon one occasion a minimum of 25 0 F. was reached. 
PUPATION AND THE PUPAL PERIOD 
The pupa (fig. 6), when found within the leaf, is always at the enlarged 
end of the mine where the larva stops feeding, and frequently in a cavity 
next to the lower surface, so that there is no indication that the pupa- 
rium is present until the leaf is turned over to view it from beneath. 
The color is light yellow at first and gradually turns darker as transfor¬ 
mation progresses, becoming a deep-brown color before the adult emerges. 
In the more humid section of the country the fully developed larva 
invariably forsakes its mine and descends into the ground from one-fourth 
to one-half inch below the surface, or crawls beneath some litter and 
there pupates. This is apparently true over the entire country with 
respect to the hibernating generation, but in the arid and semiarid regions 
of the West it has been observed that during spring and summer much 
of the transformation takes place within the larval mines in the leaves. 
In the Salt Lake Basin and alfalfa-growing sections of southern Idaho 
and Wyoming pupation occurs almost entirely within the larval mines 
during the summer months. The junior author, who first studied the 
species at Wellington, Kans., and afterwards at Salt Lake City, Utah, 
at once noticed this difference in pupation habits in the two localities. 
This same thing was noticed at Salt Lake City, Utah, by Mr. C. N. 
Ainslie, who was rarely able to find mines from which the larvae had 
emerged to pupate. 
Mr. Wildermuth found that in the Imperial Valley of California during 
the month of April about 50 per cent of the larvae pupate in the mines, 
but in the Salt River Valley of Arizona only a small percentage trans¬ 
forms within the mines, the majority forsaking the leaf and pupating in 
the soil. In Indiana, where this insect attacks cabbage, rape, and cow- 
peas, this transformation takes place entirely within the soil. This is 
also true in the region of the Southeastern States, where the mines are 
found in the leaves of cowpeas and, as observed by Mr. McGregor, to 
some extent in those of cotton. 
No reason can be advanced to explain this difference in habit of pupa¬ 
tion, a careful study of the humidity in these widely separated localities 
failing to offer any explanation therefor. 
The pupal period during the summer months is about 10 days, but 
ranges from 8 to 28 days from April to December. 
