THE SUGAR-BEET THRTPS. 5 
about on the leaf with the abdomen curved downward, but if dis- 
turbed moves rapidly away with short, quick leaps. It seldom takes 
wing, although the writer has twice observed flight for a short dis- 
tance. 
A beet leaf showing the adult at rest is illustrated in Plate II. 
The adult males are smaller and more active than the females, 
which usually greatly outnumber them, although at times the pro- 
portion becomes nearly equal. Copulation takes place during the 
day, as has been observed on a number of occasions. 
Oviposition usually takes place at night or in the evening, but has 
been observed late in the afternoon. 
DESCRIPTIVE. 
THE EGG. 
Egg (fig. 2) translucent white; surface without sculpture; elongate reniform, slightly 
flattened at cephalic end. Average length 0.249 mm.; width 0.108 mm. Deposited 
usually on the underside, obliquely to the surface, and beneath 
the epidermis of the leaf or stem. 
When the embryo begins to develop, the egg becomes swollen 
and turns dull white. 
THE NYMPH. 
First stage (fig. 3).— Fusiform, translucent white; head, eyes, Fig 2 -Eggsofsugar-beet 
, , , . . , Pii-i thrips. Enlarged, 
legs, and prothorax large in proportion to the rest of the body; (Original.) 
length 0.481 mm. 
Head sub quadrate; slightly rounded in front. Length 0.083 mm.; width at eyes 
0.103 mm. The eyes dark red, ocelli absent. Antennae, length 0.249 mm.; the seg- 
ments confused with the exception of 2 and 3, which are separate; segments 1 and 2 
cylindrical, bearing spines on outer margins; segment 2 slightly longer; segment 3 
pedunculate, annulate, bearing spine on outer anterior margin; segment 4 fusi- 
form, annulate, nearly twice as long as 3, bearing two spines on upper margin; seg- 
ments 5, 6, 7, and 8 slender and tapering toward apex; spine on outer margin of 
segment 5. The head bears two pairs of setae dorsally, and one in front of the eye 
on the outer margin. Prothorax large, transverse, rounded at the margins, bearing 
one pair of setae on lateral margin; length 0.09 mm.; width 0.146 mm. Mesothorax, 
width 0.398; mesothorax and metathorax each bear a pair of setae on outer margin, 
and one pair dorsally. Legs translucent, robust, bearing numerous short spines. 
Abdomen tapering posteriorly, segments subequal in length, with the exception 
of 9 and 10, which are longer; 9 about half as long as 10. Each segment, except 9 
and 10, bears three pairs of setae; one pair on the lateral margin, and two on the dor- 
sum; segments 9 and 10 bear 2 pairs. The mesothorax and segments 2 and 8 of the 
abdomen each bear a pair of spiracles. 
Second stage (fig. 4). — Body fusiform, translucent, tinged with faint yellow. 
Length 1.41 mm. 
Head subquadrate, rounded and narrowed in front; about as wide as long; length 
0.099 mm.; width 0.133 mm. at eyes. Antennae 8-jointed, all segments distinct ex- 
cept 7 and 8, which do not appear to be movable; segments 3, 4, 5, 6, and 7 annulate. 
Length 0.332 mm. The prothorax transverse, narrowed toward the head; width 
0.294 mm.; length 0.149 mm. Mesothoracic angles prominent; width of mesothorax 
