IOWA ACADEMY OF SCIENCES. 227 



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 mesoscutumis 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 

 tibiai stout; spines present at apex of posterior tibial and tarsal joints, on 

 inner margin of tibite 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; cilice 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 RadiaLvein is obsolete between base of wing and posterior basal cross vein, 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 x^cillkla 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 

 tibias and the number of spines on the front wings. 



