GENUS CIMBEX. 7 



down in a round curve to the apex, forming a hollow 

 with a blunt tooth at either end. The ridge on the 

 other side is much less developed, and there is also a 

 blunt ridge on the underside of the femora, which are 

 much thickened. The anterior femora are of the normal 

 size, and they are also grooved. The coxae are not 

 enlarged like the two posterior pairs. 



The abdomen is a little longer than the head and 

 thorax; the blotch is very wide, and extends nearly 

 across the segment ; the segments are nearly of equal 

 size. The ninth does not project at all on the upper 

 side. Backwards it does not extend beyond the eighth, 

 the saw does not project beyond the apex of the 

 abdomen. 



The form of the saw and back piece is quite peculiar, 

 being rounded and curved at the apex, not brought to 

 a sharp point as with the other saw-flies, and they are 

 further distinguished by having along the edge little 

 projecting bead-like points. 



The insects belonging to this genus are the largest 

 of all the TentlirediniddB. They are very variable in 

 coloration, and this has led, on the one hand, to many 

 so-called species being made out of the various forms, 

 and, on the other, to all the forms being united into 

 one species, as was done by Klug, who placed them 

 together under the name of G. variabilis. The obser- 

 vations of Brischke, Zaddach, and Van Vollenhoven, 

 however, have shown conclusively that there are at 

 least four, if not five, good European species of Cimbex, 

 s. sir. Undoubtedly the most satisfactory way of 

 discriminating the species is by rearing them from the 

 larvas. Failing this crucial test, it is not always an 

 easy matter to separate the perfect forms. In colour 

 they vary exceedingly ; the thickness, texture, and 

 colour of the hair vary ; the form of the antennae varies, 

 especially in their comparative length and in the shape 

 of the club ; the position of the nervures fluctuates : 

 thus the second recurrent nervure is found in the second 

 cellule, in the third, and is interstitial in all the species. 



