8 
BULLETIN 421, U. S. DEPARTMENT OF AGRICULTURE. 
and front of a distinct elevation on top of head between eyes. Head light brown with 
light yellowish longitudinal stripe on each side between eye and ocelli. Maxillary 
palpi three-segmented, short, small; labial palpi minute. Antennas eight-segmented, 
slender, nearly three times as long as head; relative lengths of segments as follows: 
1 2 3 4 5 6 7 8 
5 8.8 16.6 12.2 11 8.6 4.3 10.5 
Segment one cylindrical, three-fourths as broad as two, which is barrel-shaped and 
annulated; remaining segments narrower than these two and more elongated; three 
and four fusiform; seven and eight nearly cylindrical; eight very slender; one, two, 
and three nearly concolorous. light yellow with tinge of gray or brown on one and two; 
four and five light yellow in basal half, shading to light brown on apical half; six, 
Fig. 7.— Adult female of sugar-beet thrips. Enlarged. (Original.) 
seven, and eight uniformly chocolate brown ; segments two to five annulated ; spines 
slender, light colored. 
Prothorax transverse, about one-fifth wider than the head, twice as wide as long and 
shorter than the head ; sides rounded ; without conspicuously large spines. Mesothorax 
about one and two-thirds times as wide as the head; anterior angles prominent: meso- 
notumwith deep incision on posterior margin; metanotum with four spines standing 
in a square near its center. Wings present, long, about one-sixteenth as broad as long; 
fore wings broadened at base, with two longitudinal veins, the second branching from 
the first not far from the base of the wing. Spines upon veins of fore wing stout, 
dark colored, and set at uniform distances; costa bears seventeen to twenty, fore vein 
fourteen to seventeen, hind vein ten to thirteen, scale three to five besides pair at its 
tip; spines on basal fourth of wing are light colored, smaller, and much less conspicuous; 
anterior fringe on both wings fairly long and stout: posterior fringe long, slender, and 
dark colored. "Wings grayish brown to dark gray, lighter between the longitudinal 
veins; three nearly white cross bands; one across base before branching of veins, 
another at three-fourths the length of wing and the third across the tip. Legs: All 
tibia', tarsi, and fore femora yellow; middle and hind femora dark brown, yellow only 
