74 ENTOMOLOGISK TIDSKRIFT 1S94. 



little inwards on the ventral side (PI. 3, fig. i, t') outside the 

 articulation of the posterior coxas, while the sternite is completely 

 wanting. The segments externally distinctly observed are, with 

 exception of the ist and the 2nd last ones, all of the same struc- 

 ture and similar in both sexes; each consists of a tergite occu- 

 pying the back and the sides and projecting inwards on the ventral 

 side (PI. 3, fig. 9, t'*, t'') as a triangle, the inner portion of which 

 overlaps the lateral margin of the well developed sternite, the 

 result being that epimeral plates are wanting and that the pleurre 

 only are present as an articular membrane. 



In the female we count in all 9 tergites, the last of which 

 is small, and near the basis of the last but one tergite issue the 

 cerci; on the ventral side only 6 sternites are found. In the 

 male is found 11 very distinct tergites (PI. 2, fig. 2), the last 

 but one with the cerci, and 8 sternites. Consequently very essen- 

 tial differences exist in the structure of the abdomen in the two 

 sexes: no^v it is to be examined if they in reality are so great 

 as it seems externally. Examining a distended skin of a female 

 cleaned in caustic potash 2 very short tergites otherwise drawn 

 forward and concealed under the 7th tergite (PI. 3, fig. 8, t'), 

 are easily found between this and the following broad tergite, 

 which consequently becomes the loth (t'**) and is connected with 

 the cerci. Thus we have 1 1 tergites in both sexes, the 8th and 

 9th being very short and totally concealed in the female, while 

 in the male they are quite similar to the preceding. 



As mentioned above the female possesses only 6 distinct ster- 

 nites belonging to the 2nd — 7th segment; the 5 anterior sternites 

 are the usual transverse plates, but the 6th is prolonged back- 

 wards as a great semicircular lobe (PI. 3, fig. 7, s'), reaching 

 almost the hind margin of the abdomen; at the beginning of this 

 lobe is seen on each side a rather long split (a) going forward 

 through the sternite. On the above mentioned, cleaned skin is 

 seen with transmitted light under this sternite 2 narrow, curiously 

 formed plates, interrupted in the middle and obviously being the 

 sternites (s*^, s'*) of the 8th and 9th segments, transformed in this 

 manner on account of the female genital aperture. At the outer 

 margin af these two small sternites is seen in fig. 7 the ventral 

 portion of the two corresponding tergites (t^, t") and behind them 



10 



