OF WASHINGTON, VOLUME XVII, 1915 129 



Plesiothrips gen. nov. 

 (TrXrjo-ios, near; dpty, a wood worm.) 



Body depressed. Head scarcely wider than long, usually broadest 

 across eyes and constricted behind them, triangularly produced in front, 

 sides about parallel between eyes and base of antennae, the anterior ocellus 

 completely anterior to front margin of eyes. Eyes prominent, protruding, 

 much narrower than their interval. Antenna? seven-segmented, the fourth 

 longer than the third, the seventh slender, males with distinct accessory 

 "ring-joint" at base of segments 4 and 5; antennae of female nearly normal in 

 structure, those of male with third and seventh segments small and the 

 fourth to sixth elongate and bearing many long hairs which have no analogue 

 in the female; sense cones on segments 3 and 4 forked in both sexes. Max- 

 illary palpi three-segmented. Prothorax of female about as long as head 

 and but very little wider, that of male distinctly shorter; two pairs of long 

 bristles at posterior angles. Wings long and slender, the spines on anterior 

 margin of fore pair long and slender, barely distinguishable from the fringe. 

 Abdomen of the female conical at tip, spines in both sexes long and slender; 

 ovipositor vestigial; ninth abdominal tergite of male with a pair of long, 

 heavily chitinized, finger-like processes arising from strong tubercles on 

 posterior margin, in addition to four pairs of long bristles, of which an 

 approximate median pair are shorter. 



Type: Sericothrips ? perplexa Beach. 



In addition to the characters furnished by the antennae and 

 tip of the abdomen in the male, Plesiothrips may be separated 

 in the female sex from Thrips and Bagnallia by the produced 

 head, the position of the anterior ocellus, the elongate fourth 

 antennal segment, the narrow prothorax, and the almost com- 

 plete absence of an ovipositor. The appearance of "ring-joints" 

 through an actual breaking up of antennal segments is signifi- 

 cant, indeed, pointing to the possibility of evolution in the order 

 through an increase in the number of segments. Reduction 

 by fusion is of common occurrence. 



Plesiothrips perplexus (Beach). 



(Plate XV, Figs. 1-4.) 



1896. Secicothrips f perplexa Beach, Proc. Iowa Acad. Sci., Vol. Ill, p. 



216. (Ames, Iowa; on Cyperus, corn, and grass.) 

 1902. Thrips perplexus, Hinds, Proc. I'. S. Xat. Mus., Vol. XXVI, p. 184, 



PI. VI, figs. 66-68, PI. XI, fig. 123. (Amherst, Mass.; on grasses.) 

 1913. Thrips verplc.cn*. Morgan, Proc. IT. S. Nat. Mus., Vol. 46, p. 44. 



("Florida and Tennessee; grasses, ><><! and cedar.) 



Female (macropterous). Both Miss Keaeh and Dr. Hinds (loc. cit.) have 

 written good descriptions of this sex. and Hinds gives four figures. De- 

 tailed measurements are given below, and on Plate XV, figures 3 and 4 illus- 

 trate the head and prothorax and the antenna-. 



