210 Dr. David Sharp on 
But this is, of course, a mere suggestion, and still leaves 
it doubtful what the use of the enormous heads of these 
individuals can be. Before attempting to answer that 
question dissections should be made to see what is the 
condition of the nerve centres in the head, as this might 
prove instructive. 
Myrmicipes.— Cryptocerus atratus (worker). Amazons. 
In this insect the neck of the post-nodular segment is 
short and not prolonged in the middle ; the whole of the 
upper surface of the neck is densely and finely sculp- 
tured with a short transversely linear sculpture, without 
any stridulating lines on it. There is no scraping ridge 
on the hind margin of the node. 
In this insect there is apparently no means for pro- 
ducing sound by the action of these parts. 
Kicrronin1.—I have examined workers of several species 
of Eciton, and find that they have no stridulating organ, 
the sculpture being uniform all over the dorsum of the 
neck of the segment. 
The organs of stridulation consist of a file, t.e., a series 
of perfectly regular, straight lines placed on the middle 
of the dorsal region of the third abdominal segment, and 
of a scraping instrument placed on the hind margin of 
the preceding segment. ‘The file is slightly raised, and 
a little curved transversely. 
These organs appear to be absent in the Camponotides 
and Dolichoderides ; in the Ponerides and Myrmicides 
they are usually present, but are sometimes absent, and 
I think it probable that one group of Myrmicides 
(Cryptocerini) will be found to be quite destitute in this 
respect. 
The file or stridulating bands appears, in the case of 
the Ponerides, to be a development from the sculpture 
of the parts. The condition of this band, as seen in 
Dinoponera grandis and in Paltothyreus (?) commutatus, 
shows that the sculpture has only to become on some 
spot more regular and denser, and the surface slightly 
raised to transform the general sculpture into a rudi- 
mentary stridulating band. A tension acting trans- 
versely on the spot, supposing the materials not to be 
absolutely rigid, might be, I should think, capable of 
effecting the transformation. The scraping ridge is 
merely a development of the chitinous membrane by 
which the second segment is bordered behind; this 
