206 QUARTERLY CHRONICLE, 
the “‘ligament.”” In other cases a rectangularly bent “lever ”’ 
acts upon the ligament, and thus causes the occlusion of the 
tube. In the Coleoptera there are either one or two levers of 
this kind. And the same arrangement is also found in the 
Hymenoptera. 
The contraction of the muscle acting upon the lever or 
rod, as the case may be, approximates the “ ligament” to 
the “ bow,” and thus closes the apparatus. On the cessation 
of the contraction the parts regain their former position by 
their elasticity. 
An apparatus of the above kind is found, according to the 
authors, in all insects. But in some, as among the Neurop- 
tera—in Agrion, Libellula, &c.—it is reduced to a minimum. It 
is very manifest, even in minute species, as in the Pediculinz 
and Pulicide. In many cases it is so much developed as to 
constitute a sort of larynx, and as such may serve as a vocal 
organ. 
The solid chitinous parts are always connected in such a 
way, that in a state of quiescence the tracheal tube remains 
open, and gives free entrance and exit to the air through the 
stigma. Muscular action is necessary to close the apparatus. . 
This is effected in all cases by a single muscle, which differs 
in different species in the greater or less number of its fibrille. 
One end of the muscle is always attached to the extremity of 
the lever or levers, whilst the other is usually inserted into 
the occluding apparatus itself, that is to say, in the ‘* bow ;” 
but in some cases in the hypodermis close to the stigma, in 
which case there is provision of thin vibratile membranes. 
The authors then proceed to point out that a closing appa- 
ratus of some kind to the trachee must be required in all 
insects, inasmuch as the movement of the air in the trachee 
can only be effected by the movements of the body or 
muscles, &c., which, were the exit of the air at all times free, 
would have as great a tendency to expel it through the 
stigma, or even a greater than to force it onwards into the 
minute ramifications of the tracheal system. 
The remainder of the paper, which occupies nearly thirty 
pages, and is illustrated by beautiful figures, is taken up with 
a description of the modifications presented by the occluding 
apparatus in various insects. 
1. Among the CotropreRA in Cicendula campestris, 
Geotrupes vernalis, Meloe proscarabeus, Curculio nebulosa, 
Melolontha vulgaris, Hydrophilus piceus, Lamia textor, 
Lucanus cervus. 
2. Among the Lrpipoprera in Pieris rahe, Vanessa 
urtice, Cossus ligniperda, Pygera bucephala. 
