THE SUGAR-BEET THRIPS. 9 
at ends; spines upon legs small and inconspicuous except ten to twelve on inner side 
of hind tibise. 
Abdomen broadly ovoid, conical at tip, twice as wide as head; ovipositor long and 
slender; tenth segment split open above; segments two to eight with dark cross line 
near anterior edge. Two or three spines on sides of each segment from two to eight, 
not conspicuous ; anal spines weak. Color of abdomen yellowish brown to dark brown ; 
last two segments much more yellow, but shading to brown at posterior edges. 
This species has the power of springing. 
A description of the male, which hitherto has not been recognized, 
is appended. 
Male. — The male resembles the female in appearance, but is much smaller and more 
active. The abdomen tapers gradually posteriorly; the apex (fig. 8) is truncate; the 
Fig. 8.— End of abdomen of male of the sugar-beet thrips. Greatly enlarged. 
Drawn by J. D. Hood. (Original.) 
last segment is short and broad. Segment 9 bears dorsally three pairs of short, black, 
obtuse spines, light brown at the base; two pairs near the middle of the segment, and 
one pair near the posterior margin, and more widely separated. 
Measurements: Length of head 0.099 mm.; width of head 0.174 mm.; width of 
prothorax 0.199 mm; length of prothorax 0.0996 mm. ; width of metathorax 0.282 mm. ; 
width of abdomen at third segment 0.299 mm.; length of abdomen 0.73 mm.; length 
of antennae 0.299 mm. Total length 1.185 mm. 
LIFE CYCLE. 
The life history was determined under natural greenhouse condi- 
tions. Females were isolated on small beet seedlings, and as soon as 
they deposited eggs the adults were removed. The temperature and 
moisture were fairly constant, the maximum temperature being 
