INTERNAL ANATOMY OF INSECTS. 159 
A. viridissima this organ is straight, in A. verrucivora 
bent like a sabre, and in Pterophylla citrifolia and some 
others, the whole machine is short and boat-shaped ; in 
Scaphura Vigorsii it is also rough with sharp little tuber- 
cles *. I had an opportunity of observing, with respect 
to the first of these insects, that in boring, as is the case 
with the Cicada and saw-flies, the motion of the valves 
was alternately backwards and forwards. It appeared 
also to me that the two outer pieces of each of the ap- 
parent valves were fixed in a groove in the margin of 
the intermediate one. I saw this clearly with respect to 
the upper pieces, and it is most probable that the lower 
are similarly circumstanced. In the cricket tribe (Gryllus) 
the ovipositor is as long as the abdomen, very slender, 
terminating in a knob b . It is apparently bivalve like 
that of Aerida, but I believe is resolvable into the same 
number of pieces. 
In the Homopterous Hemiptera there seems to be more 
than one type on which the ovipositor is constructed. In 
an insect very common with us, the froth froghopper 
(Cercopis spumaria), some approach is made to the ovi- 
positors last described, at least the number of pieces is 
the same — for it has a pair of external valves forming a 
sheath, which includes three sharp lamina: resembling 
the blades of a lancet, the middle one of which can be se- 
parated into two ; this instrument De Geer had reason 
to think was scored transversely like a file c . In the in- 
sects of this Order so noted for their song 1 ' (Cicada), 
there are only Jive pieces ; namely, two valves forming the 
* This insect, which connects Cnnocejihalus, Aerida, &c. with Lo- 
custa, is also distinguished by antennas at first filiform and then 
setaceous. h De Geer iii. /. xxiv./. 1, 12. 
e Ibid. 17fi. t. xi./. 19. * Vol. II. p. 307—. 
