THE CITRUS 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-instar 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°— 18— Bull. 616 3 
