THE SUGAE-BEET THKIPS. 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 wi'iter 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. 



TMien the embryo begins to develop, the egg becomes swollen 

 and tmns dull white. 



THE NYMPH. 



First stage ( fig. 3) .—Fusiform, translucent white ; head , eyes, Fig 2.-Eggsof sugar-beet 

 1 \ , . . 1 \. 1 1 1 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 setse 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 Vjcar a pair of spiracles. 



Semnd slaye (fig. 4). — Body fusiform, translucent, linged with faint yellow. 

 Length L41 mm. 



Head Hiibquadrate, 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- 

 frept 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 



