IOWA ACADEMY OP SCIENCES. 
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an elongate oval; joint 6 is longer than any other joint; joints 7 and 8 are 
short and of equal length, base of former narrower than apex of 6; apex of 
8 is lanceolate. Bristles and hairs are of equal size, and arranged much as 
in T. tritici. The long sensorial spine on outer side of joint 6 originates 
below the middle of the joint. 
The prothorax is convex; its sides converge cephalad; its surface is 
nearly smooth , with a double median transverse groove or double impressed 
line and a few short and several long slender bristles, the latter arranged as 
follows: one at each anterior angle, two on intervening space of anterior 
border, one at middle of each side, one near and two at each posterior 
angle. The mesoscutum is longitudinally convex, its surface nearly smooth, 
furnished with two lateral bristles directed inward, and two smaller ones 
on disc and on posterior border, respectively. The scutellum is subrec- 
tangular, obtusely carinated, descending toward the apex; on basal margin 
provided with two distinct bristles which extend nearly to apex. 
The abdomen is slender at base, ovate, with few conspicuous bristles; 
those at apex of ultimate segment much shorter and weaker than those on 
preceding segment. 
Legs are moderately stout, bristly; anterior femora incrassate, their 
tibias stout; spines present at apex of posterior tibial and tarsal joints, on 
inner margin of tibiae replaced by bristles. 
The anterior wings are whitish, slender, rather thin, subfasciate with 
three dusky spots; the first near base of anal area, the other two dividing the 
remainder of the wing into three subequal parts; sometimes a faint spot 
may be detected near apex of wing; these spots are variable in distinctness 
and may be obsolete; ciliae of inner margin, light; of outer margin, sparse 
and scarcely longer than the spines with which they are interspersed. 
RadiaLvein is obsolete between base of wing and posterior basal cross vein, 
consequently it appears to originate in the cubitus. Both radius and cubi- 
tus terminate abruptly before attaining marginal vein. Cross veins con- 
necting costal and cubital veins are obsolete. The costal vein bears from 
15-20 spines; the cubital, 10; radial, 5; anal, 4, and posterior marginal vein 
1, placed opposite the posterior basal cross vein. The posterior wings are 
hyaline; proximal end of longitudinal vein incrassate. 
Male. Length .97 mm. Smaller than the female, but very similar in 
distinctive characters. Apex of abdomen is bluntly conical, less truncate 
than in male of T. tritici, partially trilobate, the lateral lobes are very 
narrow, shorter than the middle lobe, and terminate in a single long 
bristle. Penultimate segment terminates in a row of short sparse bristles, 
on dorsum, and single long spine on each side. 
Described from ten females and seven males. Taken on bean 
and elm at Ames, Iowa; on blackberry at Belle Plaine, Iowa, 
and on hop at Barraboo, Wis. 
Thrips pallida is a well marked species and is readily sepa- 
rated from the other species included in this paper by the small 
head, the presence of a bristle on middle of lateral margin of 
prothorax, the feeble armature of inner margin of posterior 
tibise and the number of spines on the front wings. 
