MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
531 
of the body, even into the substance of the brain and nerves. The longitudinal 
tracheae communicate freely with each other across the body, both at the anterior 
and posterior part of the insect, and along the whole dorsal and ventral surfaces, by 
small ramifications of the tracheae from each side meeting and anastomosing together. 
At the anterior part of the body there is also a large tracheal tube communicating 
between the tracheae of the sides. It is situated in the second segment, and extends 
into the base of the first, where it gives off, immediately behind the brain, four prin- 
cipal branches, which are distributed forwards over the brain and head. Two of these 
go to the antennae, and the others to the anterior and upper part of the head. There 
is also a large branch from the under surface of the longitudinal trachea in the second 
segment, which communicates across the under surface of the segment with a corre- 
sponding one from the opposite side. This is the general arrangement of the tracheae, 
particularly in the larva state of insects. The larva of the Bee has the tracheal ves- 
sels very small, but freely communicating around the body, as was shown by Swam- 
merdam. The same insect in its perfect state has these communications still existing, 
but the whole of the principal tracheae are then developed into large vesicles or bags. 
This is the case even with those tracheae which traverse the under surface of the 
abdomen, although the tubes of communication are not obliterated [Plate XXXVI. 
fig. 2. g.]. All volant insects in their perfect state have the respiratory organs of the 
same vesicular structure. 
The vesicles, as was shown by Swammerdam * and Sprengel, are covered with in- 
numerable punctured spots, which are only perceptible under a good microscope, and 
when attentively examined exhibit somewhat the appearance of perforations. Marcel 
de Serres and Straus Durckheim deny the existence of spiral fibre in these vesicles, 
but Suckow and BuRMEisTER-f- are of opinion that it really does exist, and I am myself 
disposed to maintain the same view. Indeed when we remember that the vesicles 
exist only in the perfect insect, and are only dilated tracheae, and that in tracheae the 
existence of spiral fibre is undoubted, it surely cannot be questioned that it exists also 
in the vesicles, although probably in a very attenuated state, and almost atrophied. 
The nature of the punctured spots in the vesicles is of some interest, since I am not 
aware that they have been distinctly observed until after the insect has passed 
into the perfect state. Burmeister, who contends for the existence of spiral fibre in 
the vesicles, conceives that these spots are occasioned by the rupture of the spiral fibre 
during development, and are formed by the interspaces between the portions of rup- 
tured fibre. That this cannot be the case is proved by the existence of these spots in 
some of the tracheae which communicate directly with vesicles, and have not been 
dilated, in which the spiral fibre is distinctly seen to be unbroken ; and also by 
the circumstance of their not being in a regular ^series, or in the course of the 
fibres in the vesicles, but distributed thickly and irregularly over the surface of 
the whole vesicle, and by their existing between two parallel fibres, and even in the 
* Biblia Naturae, Plate XXIX. f. 10. f Manual of Entomology, translated by Siiuckard, 1836, p. 181. 
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