Oct. 10,1913 
Serpentine Leaf-Miner 
73 
tion was noticed on alfalfa plants growing in the bottom of a dry irrigation 
ditch where the vertical banks on each side kept the plants well shaded. 
At the same time very few mined leaves could be found in the open fields. 
There was, however, no interruption to the generation experiments car¬ 
ried on out of doors and in the shade at Salt Lake City, the adults con¬ 
tinuing to emerge and larvae to develop during this time. 
Mr. Wildermuth, at Tempe, Ariz., during the season of 1912, remarked 
the almost total disappearance of all stages during the months of July 
and August, followed by their reappearance in September. He recorded 
three generations from the last of April to the last week in June and two 
more and a partial third generation between September and December 
of the same year. At Tempe adults did not emerge from the puparia 
in the generation experiments during July and August. 
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Fig. S.—Diagram showing the range in temperature throughout the year at three widely separated 
localities at which observations were made on the serpentine leaf-miner. 
In Arizona this disappearance of the insect apparently takes the form 
of a period of aestivation during the hot weather of midsummer, when 
the temperature in the open fields is too high for the successful propaga¬ 
tion of the species. This is less noticeable in the cooler alfalfa-growing 
valleys farther north, where the summers are milder. Its presence in 
Utah alfalfa fields in much reduced numbers during August indicates that 
an attempt at aestivation is made there, but over a period of much shorter 
duration than is found farther south, in Arizona. 
In this connection we here present (fig. 8) curves representing the 
normal mean temperatures recorded by the United States Weather 
Bureau at Salt Lake City, Utah, and Phoenix, Ariz. As will be seen by 
these curves the normal temperature at Phoenix, Ariz., from the first of 
