64 Hood — Neiv Genera and Species of N. A. Thysanoptera, 



light which it seems to throw on the evolution of the Thysanoptera. 

 These genera probably represent the" most primitive known members of 

 the order; for in no group of insects does specialization result in an increase 

 in the number of segments either in the body or its appendages. Stoma - 

 tothrips is thus best placed at the beginning of the JSolothripidse, possess- 

 ing as it does more palpal segments than any other known genus. 



In an ancient type we would expect to find broad wings; and this is 

 actually the case. Although the palpi of Paheothrips fossilis Scudder,* 

 a Tertiary species described from the White River deposits of Utah, are 

 unfortunately unknown, it is interesting to note that the fore wings are 

 broad and similar in venation to those of Stomatothrips, though a little 

 wider in proportion to their length. 



Carrying these generalizations a little further, — if we may safely do so 

 on such scant evidence, — we are led to the conclusion that the order 

 Thysanoptera originated in or near the tropics of the New World. And 

 early in its evolution it seems that a branch diverged to form the Uro- 

 thripidse (at present known only from the Old World) which, having in 

 the course of their adaptation lost the ovopositor they at one time pos- 

 sessed, naturally approach the Tubulifera in general appearance. Mr. 

 Bagnall has already notedf that in many fundamental characteristics the 

 Terebrantia and Tubulifera resemble each other more closely than do the 

 Urothripidse and Phloeothripidie; but he nevertheless assigns the family 

 Urothripidse to the Tubulifera. In my opinion the family should be made 

 the type of a new sub-order abundantly distinguished by the presence of 

 eleven instead of four spiracular openings — certainly a character of high 

 taxonomic value in view of its constancy in the two sub-orders at present 

 recognized. 



Stomatothrips flavus sp. nov. 

 Fig. 1, a and b. 



Female. — Length about 1.6 mm. (1.47-1.77 mm.). Color testaceous, 

 head and prothorax slightly darker; pterothorax with an indistinct, V- 

 shaped, brown cross-band at middle of dorsum ; abdomen with faint 

 indications of a pale cross-band on segments 1, 2, and :>; antennal seg- 

 ments 1-4 pale yellowish white, the remainder of antenna black; tibise 

 shaded with black. 



Head about one and one-fourth times as wide as long, rather deeply 

 sulcate between antennae, and slightly narrower and shorter than pro- 

 thorax ; cheeks slightly arcuate; dorsal and lateral surfaces faintly trans- 

 versely striate, set with numerous minute spines. Eyes large, pilose, 

 posteriorly prolonged on ventral surface, and with large, distinct facets. 

 Ocelli ecpiidistant. Antennae moderately slender, about as long as com- 

 bined lengths of head, pro- and mesothorax; segment 1 broadest, nearly 

 as wide as long, tapering toward apex; 2 distinctly longer and narrower 



•Proc. Bost. Soc. Nat. Hist., Vol. XI, p, 117, 1867; Geol. Mag., First Series, Vol. V, 

 p. 221, 1868; Bull. U. S. Geol. Surv. Terr., I, p. 222, 1875. 



t Proceedings International Entomological Congress, II, 283-288; 1911. 



