562 
MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
Insects generally recover, although very slowly, after confinement in carbonic acid 
for a few minutes ; but they very seldom recover after confinement in a mixture of 
sulphurous and nitrous acid gas, or chlorine, which appear to affect them as direct 
and specific poisons. The rapidity with which these gases affect the respiration of 
insects depends upon the peculiar habits or natural constitution of the species. Thus 
insects accustomed to inhabit the open atmosphere, Lepidoptera and Hymenoptera, 
are affected almost instantaneously and perish quickly by these gases, while those 
which are accustomed to inhabit noisome places, as the Carabi and Geotrupes, are 
either not affected, or recover from their effects much sooner. A specimen of Geo - 
trupes vulgaris, Steph., when confined in a mixture of sulphurous and nitrous acid 
gas, was visibly affected in thirty seconds, and apparently completely asphyxiated in 
two minutes ; but on being removed immediately to the open air, it was completely 
recovered in from twenty-five to thirty minutes. But an individual of the same spe- 
cies, when confined in chlorine, was powerfully affected in less than twenty seconds, 
and became completely motionless in two minutes ; and although it was immediately 
removed to the open air, it hardly gave any signs of life for more than twelve hours 
afterwards, and even then it did not ultimately recover. We have thus a distinct 
proof of the poisonous nature of these gaseous bodies, and of their comparative viru- 
lence, and that the respiration of insects is affected by them in precisely the same 
manner as the respiration of vertebrated animals, the only apparent difference ap- 
pearing to arise from a peculiar habit of body which resists their effects for a longer 
or shorter period. But the most deadly of all media is hydrocyanic acid in a 
state of vapour, admixed with atmospheric air. If an insect be confined over the 
fumes of hydrocyanic acid, it perishes almost instantaneously if the gas be powerful, 
but if only a small quantity be mixed with atmospheric air, the insect is paralysed for 
a time, but will ultimately recover. This difference between the effects of hydro- 
cyanic acid gas and chlorine is very interesting. The instantaneous manner in which 
hydrocyanic acid gas, or rather cyanogen, destroys life and suppresses every act of 
respiration and volition, when respired by the insect, sufficiently proves that it cannot 
be by its admission into the circulation of the body, and that its being received into 
the system of tracheal tubes is sufficient to enable it to act upon the nervous system 
instantaneously. Even those insects which in every other medium are exceedingly 
tenacious of life, even in the deadliest, chlorine, perish in an instant in cyanogen. 
The insect dies in a tetanic state of contraction of all the muscles of the body. 
Chlorine, on the contrary, appears to kill by producing in the first place a rigid spasm 
of the respiratory organs, and a congested state of the mucous membrane, which 
renders respiration at first difficult and at length impossible. 
From these circumstances I have been led to conclude that the manner in which 
the respiration of insects is affected by noxious media is the same as in Vertebrata, 
and that life is destroyed by them in precisely the same manner in both divisions of 
the great kingdom of animated nature. 
