Hansen: on six species of koenenia. 209 



more numerous than the setje in the above-mentioned whorl, 

 only about half as long as their joint, and while the very long 

 setae in the whorl on the thickest place stand out almost at 

 right angles to tlie surface, the setœ in the subapical whorl are 

 directed almost backward and lie rather close to the surface of 

 the following joint. In the seven other joints of the flagellum 

 the subapical whorl is quite wanting. Now we have seen the 

 more coarse structural features of the flagellum, but a closer 

 examination reveals still several interesting points. Then it is 

 perceived that the whorl of shorter glabrous setae on the six- 

 joints mentioned is inserted on a very short subjoint (pi. 2, fig. 

 I f, p), which proximally is separated from the main joint (a) by 

 a membrane. In an extended flagellum, a portion of which is 

 shown in fig. i f., the subjoint forms the apical part of the joint, 

 and the bases of its setae are free; in a contracted flagellum 

 the subjoint is retracted into the terminal part of the main joint, 

 where it is seen as an exceedingly short ring of proportionately 

 rather thick chitine, and the bases of its setae are covered by 

 the membrane at the end of the main joint. The second, 

 third, fourth, sixth, eighth and tenth joints, that is to say the 

 joints having their basal third covered by the whorl of the 

 preceding joint, offer another curious feature: the basal part 

 is subcylindrical and marked oft' by a transverse suture as a 

 very short ring (fig. i f, q) or subjoint from the main joint (b), 

 but the suture does not allow any movement; in extended spe- 

 cimens this very short subjoint is quite free, in contracted spe- 

 cimens it is retracted into the preceding joint or, more correctly, 

 into the subjoint with the whorl of glabrous setae (pi. 2, fig. id, 

 showing the outline of some joints without indication of the 

 subjoints, which scarcely could be represented with this enlar- 

 gement, when the two subjoints are retracted into the apical 

 part of the preceding main joint and besides the one subjoint 

 into the other). — The basal portion of the first joint of the 

 flagellum is marked off plainly as a separate very short joint 

 with four shorter marginal seta^ of almost equal length; I believe 

 that this short joint, which is articulated to the end of the ab- 

 domen, is t[uite the same thing as the basal part or basal sub- 

 joint of the second, the third and the other joints just described. 



Entomol. Tidskr, Arg. 22, H. 4 (1901). \n \a 



