THE OITEUS THRIPS. 



15 



in color. The antennae are directed forward and are 4-jointed. The 

 eyes, at first almost colorless, finally show a red pigmentation in about 

 two-thirds of the facets. The wing pads, which are almost colorless, 

 transparent saclike projections, the hind pair pro- 

 jecting slightly farther than the fore pair, extend 

 to or slightly beyond the hind margin of the second 

 abdominal segment at the beginning of this in- 

 star and reach to the hind margin of the third 

 segment before transformation to the second-instar 

 pupa. 



The second-imtar pupa. — The second-instar pupa 

 (fig. 7) is at first but slightly larger than the 

 advanced propupa. The color is pale, translucent 

 yellowish. The antennas are apparently 4-jointed, 

 but the exact number of joints is confused by the 

 ringed appearance due to transitional tissues seen 

 through the pupal sheath. They are directed 

 backward over the head and prothorax, extending 

 to a point near the middle of the latter. All facets 

 of the eyes are red pigmented. The ocelli are 

 visible and translucent. The wing pads at first 

 extend to the hind margin of the sixth abdominal segment or slightly 

 beyond, but project as far as the ninth or tenth segment just before 

 the molt to the adult. Long weak spines are moderately conspicuous 

 on antennae, legs, and hind angles of the ab- 

 dominal segments. 



There is less growth in the pupal stage than 

 in the larval stage. The average length soon 

 after the molt to the propupa is 0.70 mm. 

 (about 0.027 inch) ; shortly before the first 

 pupal molt it is 0.72 mm. Just before the last 

 molt it averages 0.80 to 0.84 mm. (about 0.03 

 inch). The wing pads increase on an average 

 about 0.04 mm. in length during the first in- 

 star, and show a gain after molting to the 

 second instar of 0.10 to 0.12 mm. After the 

 molt to the adult stage the wings exceed the 

 tip of the abdomen. 



Fig. 6. — First-instar 

 pupa of the citrus 

 thrips- Highly 

 magnified. ( Orig- 

 inal.) 



Fig. 7. — Second - instar 

 pupa of the citrus 

 thrips. Highly mag- 

 nified. (Original.) 



PLACE OF PUPATION. 



Certain Thysanoptera, notably the pear 



thrips, congregate in large numbers during 



pupation, and a knowledge of this habit may lead to a means of 



effective control. The citrus thrips, however, has no definite place 



of pupation. The second-instar pupa is more exposed to the attacks 



13138°— IS— Bull. 616 3 



