EXTERNAL ANATOMY OF INSECTS. 713 
may be denominated false or blind spiracles. Again, if 
you examine the pupa of any Scutellera or Pentatoma, 
in which tribe the true spiracles are ventral, you will 
discover, placed in a square on the two or three interme- 
diate dorsal segments, four or six elevated points resem- 
bling spiracles, but not perforated, connected often by 
corrugations in the skin or crust *; in the larve also of 
some Jteduvii the first minute dorsal segment, at each 
lateral extremity, has a similar elevation with a central 
umbilicus precisely resembling a spiracle, but still not 
perforated: another instance of false spiracles in this sec- 
tion of the Hemiptera, is furnished by Aradus laminatus 
before mentioned, in the perfect insect; between the 
spiracle and the margin of each ventral segment is a 
white round callus, with a dark point resembling a 
perforation on its exterior side, and terminating inter- 
nally in a channel covered by membrane leading to the 
disk of the segment, so that the whole in shape resem- 
bles a tobacco-pipe>. A number of similar callosities 
with a central impression, but without any channel, va- 
riously disposed, are also to be found in another bug, 
Rhinuchus compressipes®. In the Homopterous section 
of this Order, a series of impressed points, which may 
be easily mistaken for spiracles, are to be discovered on 
both sides of the abdomen, at the margin in Centrotus, 
in which the real spiracles are quite concealed. 
In spiders, as we learn from Treviranus, the open ven- 
tral spiracles of the scorpion are replaced by pseudo- 
* Prats XXIX. Fic. 22. is part of the back of the abdomen of the 
pupa of a Pentatoma. a the pseudo-spiracle, 5 the connecting corru- 
gations, 
' Ibid. Fic. 24. a. © Ibid. Fic. 27. a. 
