1875.] 141 [Osten Sacken. 



less variation). Between the following two extremes, all intermedi- 

 ate stages occur. 



1. The smallest specimens, from 7 mm. upwards, in length, 

 have the yellow stripes on the third and fourth segments quite 

 straight, not attenuated before coming in contact with the lateral 

 margin; their hind borders show no perceptible concavity or con- 

 vexity; such specimens usually have a distinct brown ring on the 

 hind femora, a little before the tip. 



2. Larger specimens, up to 11—12 mm. long, have the stripes on 

 the third and fourth segments with a distinctly biconvex hind mar- 

 gin, with a sinus in the middle; these stripes are distinctly atten- 

 uated on each side, before reaching the lateral margin. Such large 

 specimens often have no brown ring on the hind femora. 



Male. Differs from the female in the femora being black at base; 

 the four anterior ones for about one third of their length; the hind 

 ones altogether black or brown, except at the tip. The majority of 

 the specimens before me are of medium size (about 8-10 mm.); but 

 some larger ones also occur. The shape of the yellow bands does 

 not vary as much as in the female; they always are attenuated at 

 both ends and biconvex posteriorly, with a sinus in the middle. The 

 altogether glabrous eyes easily distinguish S. rectus d, from S: tor- 

 vus d\ in other respects they look very much alike. The average 

 size of & rectus d", is a little smaller. 



Minor differences between S. torvus and S. rectus, available for 

 both sexes, are: — 



1. The face under the eyes is altogether yellow here; there is no 

 grayish spot, as is always visible in S. torvus. 



2. The sides of the face in S. torvus is beset with very distinct 

 blackish pile; in S. rectus this pile is of a pale color, and almost 

 imperceptible; hence the face looks smoother. 



3. The antenna? are less dark, more reddish in S. rectus. 



4. The scutellum is of a slightly purer yellow. 



5. The four anterior tarsi are less brown, more reddish, especially 

 on the first joint. 



6. The contact of the abdominal yellow spots and bands with the 

 lateral margins, is slightly broader in S. rectus; hence, the yellow 

 prolongation or neck of the spots on the second segment is broader, 

 and, consequently, seems to be shorter. 



7. The stigma of the wings is much paler, yellow rather than 

 brown. 



