NO. 1310. NORTH AMERICAN THYSANOPTERA—HINDS. 217 



are generally distributed over segments six, seven, and eight, and 

 from three to five whorls of small spines are often discernible around 

 the middle half of each intermediate segment. Sense cones are found 

 upon segments three to six, inclusive; in some cases these are all sim- 

 ple, though in the majorit}^ those upon segments three and four are 

 dou])le or crescentic in form. The antenna? of ^Eolothripida^ have 

 always nine segments, of which the intermediate ones are always much 

 elongated and regularly cylindrical in form. Stout spines are found 

 only around segment two, while the remaining segments, except the 

 basal, are thickly set with small spines, which are irregularly, but 

 generally distributed. Of these last two t3^pes of antenna, that of 

 Thripidic unquestional)ly approaches more closely to that of Phloeo- 

 thripida'. Granting that the latter exhil)its the extreme degree of 

 divergence from the original type, we must place Thripida? next, and 

 this leaves the antenna of ^^^]olothripidi\3 as resembling most closely 

 that of Prothysanopteron. 



If we examine the wings in like manner, we shall find that both 

 pairs of those of Phloeothripida3 are similar in form, long, slender, and 

 rounded at their ends. Ring vein and cross veins have entirely disap- 

 peared. Each wing has only one longitudinal vei-ii, which is median 

 and though quite strong at its base usually disappears before the mid- 

 dle of the wing. The fringes upon both margins are equally well 

 developed and quite similar in all respects. The membrane of the 

 wing is smooth and the veins are not set with spines except for about 

 three, which usualh' stand near the base of the vein in the fore wing. 

 Thripidie have wings which differ in many regards from those of 

 Phloeothripida? just described. The fore and hind winys are dissimi- 

 lar in many respects. They are both, however, long, x^vj slender 

 (except the fore wing of Parth'enothvl])^^ and sharply pointed at the 

 tips. The fore wing is alwa3's somewhat stronger than the hind wing 

 and has more veins and heavier fringes. There are usually present in 

 it two fully developed longitudinal veins (sometimes only one), and 

 these disappear before reaching the end of the wing. The ring vein, 

 though very strong in the one species of Parthenothrl'ps^ is weakly 

 developed in most species and in some is hardly distinguishable. 

 Traces of cross veins can sometimes be seen, but they are never 

 strongly developed except the one between the two longitudinal veins 

 at the first third of the wing. While entirely absent (with the excep- 

 tion named as strongly developed) in most species, there may occa- 

 sionally appear individuals having wings which show traces of cross 

 veins, and it is very significant that these ahva3"s occur at just the 

 same positions in the wing as are occupied b}' the cross veins of ^Eolo- 

 thripida?, which will be more fulh^ described in connection with that 

 family. The hind wing has one longitudinal vein which is median, 

 but no ring or cross veins are present. Fringes usualh' occur upon 



