576 Mr. Cameron’stes on Hymenoptera, 
Agrees with varispinus, Htg., in having the lower part 
of the stigma, recurrent and transverse nervures, white, 
and in the form of the head; but it is smaller and 
narrower, the punctuation on head and thorax is finer and 
closer, cenchri larger and of a clearer white, the trans- 
verse radial nervure is not received close to transverse 
cubital, and the transverse nervures in posterior wings 
are wider apart. As in varispinus, the base of hind 
tarsi is generally white, but is occasionally black, and 
the spurs are in some cases blackish, in others wholly 
white. The saw is different from that of varispinus. It 
is smaller, as a rule, than @neus. 
Common and widely distributed. 
From an extensive examination of the ovipositor in the 
Tenthredinide, | have become convinced that its form 
affords us an almost absolute test of specific distinctness, 
and that its examination ought never to be neglected 
when describing as new, any doubtful forms. This is no 
doubt a troublesome proceeding, but it is certainly worth 
the labour when we consider that it enables us to define 
the limits of species to a very great extent indeed. I 
think then that no apology is needed if I describe my 
method of mounting and preserving the “saw” for 
microscopic examination, the more especially as the 
method can be applied to microscopic mounting generally. 
With fresh specimens the saws can be extracted very 
easily by pressing the abdomen, when they will be pro- 
truded and readily extracted. With old specimens it can 
be done equally well by placing the insect in a relaxing- 
dish, or, more promptly, by steeping it in water for a day, 
when they can be taken out in the same way as with 
fresh insects, the only difficulty beimg experienced with 
insects full of eggs. For their better examination the 
four pieces composing the ovipositor proper should be 
separated ; after which they must be steeped in turpentine 
for a day or two so as to get rid of air. This is best done 
by enclosing them in a small folded piece of paper ; and, 
if they be properly labelled, many different preparations 
can be placed in the turpentine-bottle together.* 
* In the case of such organs as the mouth parts (palpi, &e.), I 
find it an advantage, after dissection, and when they are ready for 
mounting, to place the papers containing the preparation inside a 
book for a day or so, as by doing so the parts retain their position 
better, and are not so apt to curl up. 
