220 IOWA ACADEMY OP SCIENCES. 



order named; the third nearly as long^ as the sixth; apical joints subequal, 

 minute; all joints thinly covered with microscopic hairs; bristles or stiff 

 hairs on basal and intermediate joints which on distal joints are replaced 

 by slender hairs; sensorial spines on the third, fourth and sixth joints, dis- 

 tinct; clypeal, subantennal and postocular bristles present, the last less 

 conspicuous than in tritici; mouth parts distinctly asymmetrical; each joint 

 of maxillary palpi cylindrical, narrower than the preceding^; first and third 

 subequal in length, and second shorter than either. 



Prothorax about one and one-half times as broad and equally as long as 

 preceding segment; anterior angles rectangular, posterior rounded, sides 

 slightly converging cephalad; disc striate and sparsely hairy; front and 

 hind borders more deeply striate or rugose, bristly; the most conspicuous 

 bristles are arranged as follows: One long bristle at each anterior ar d two 

 at each posterior angle; two shorter bristles on anterior margin, two on 

 posterior margin and one on disc near each posterior angle. 



Meso-metathorax, subquadrate; mesoscutum more finely striate than 

 prothorax, with small bristles, one at each lateral angle, two near and two 

 on posterior margin; scutellum as long as mesoscutum, narrow, not strongly 

 carinate; base transversely striate, sides longitudinally rugose; basal 

 bristles as in tritici. 



Abdomen broad, ovate, basal segments and sides sculptured, bristles 

 similar to those of tritici. 



Legs, with numerous short bristles; all tibife and joints of posterior 

 tarsi with terminal spines; anterior femora incrassate, their tibite stout. 



Wings rather broad; humeral arch not prominent; surface minutely 

 pilose; veins distinct, uniformly and heavily spiaose; anterior and poste- 

 rior basal cross veins present; cubitus inserted in marginal at tip of wing; 

 radius obsolete at proximal end, but perceptible before it unites with the 

 posterior basal cross vein; costal spines longer than those on the other 

 veins, numbering from twenty-five to twenty-nine; cubital, from nineteen 

 to twenty-three; radial, from fifteen to sixteen; anal, five, gradually 

 increasing in size from one to five; internal, one; posterior wings hyaline; 

 longitudinal vein indistinct, except at base. 



This form approaches closely the dark colored specimens of tritici, from 

 which it may be separated by its larger size, the annulus on the antennae, 

 and especially by the shape of the head, which is pentagonal instead of 

 rectangular, and the less approximate antenn;y. 



Described from twenty-nine specimens taken at Ames, Iowa, in July, 

 August, September and January. 



Thrips variabilis n. sp. 



Head transverse Antennas eight-jointed, distant; ocelli approximate. 

 Each posterior angle of prothorax provided with a single medium sized 

 bristle; bristles on penultimate segment of abdomen not strongly radiat- 

 ing, not extending backward beyond the base of the succeeding i*ow; radial 

 vein bispinose, obsolete; leg.s slender. 



Female. Length from .84-1.23 mm. Head one-half as long as 

 broad; viewed from above, subrectangular; anterior margin straight; occi- 

 put short, transversely convex and striate; distinct oblique depression 

 behind each eye; gense moderately full; vertex abruptly ascending, tumid 



