NOTES ON THE CUCUMBER BEETLES. 
73 
Mr. Marsh wrote further of this species and its occurrence at Tustin, 
Cal., that the peanuts were growing in sandy soil, and injury was every- 
where apparent, but that larvae and pupae occurred September 28 
only in spots in the heavier sandy soil. Here there were from one 
to twenty. Usually, however, there were from three to five to almost 
every plant, located from 2 to 3 inches below the surface. Most of 
the larvae had matured. The pupae were found in very fragile cells, 
and many of these were maturing, and there were many adults on 
the foliage and many soft, newly formed ones in the soil. The fact 
that the heavy soil is more moist and cooler than the lighter sand 
probably accounts for the later maturing of the beetles in such loca- 
tions. Up to December 17, the species, according to Mr. Marsh, 
had not gone into hibernation, the adults being still moderately 
common on spinach, lettuce, mustard, and 
other plants . They were flying or crawling 
about quite actively during the warm part 
of the day, and appeared to prefer spinach 
as a food plant. 
DESCRIPTIVE. 
The beetle of this species (fig. 22) differs 
from the common twelve-spotted cucumber 
beetle (JDiabrotica 12-punctata) by hav- 
ing the entire lower surface black. In 
a good series of specimens at hand it is 
noticeable that even in preserved speci- 
mens the species under discussion preserves 
more of the natural green color than does 
the eastern species. The twelve spots are 
located and arranged about the same in the two species, but in D. soror 
there is a strong tendency to the union of at least one pair of spots on 
each elytron or wing cover. The pair of middle spots are most often 
confluent or united, and occasionally both the middle and the posterior 
spots unite. This is rare in the eastern species. In the latter, the 
lower surface, including a portion of the femora, is yellow. There is 
no great difference in size, but the eastern species will average a little 
larger. The antennae are almost piceous, the basal three joints are 
slightly paler, and the thorax is less transverse. The length is about 
6 millimeters. 
This species occurs from Oregon, where it is common, southward 
through California to Arizona, and perhaps extends into Mexico. 
The immature stages of this species have been described by Mr. 
R. W. Doane. a 
Fig. 22.— The western twelve-spotted 
cucumber beetle (Diabrotica soror): 
Female beetle, about 6 times natural 
size. (Original.) 
a Journ. N. Y. Ent. Soc, Vol. V, pp. 15-17, 1897. 
