OF INSECTS. 
185 
tion, other authors are inclined to place it in the 
tracheae, either in their external margins or interior 
ramifications. Cuvier is of opinion that they are very 
well calculated to perform the office, the internal 
membrane being soft and moist, and fitted to receive 
odours from the air.* It must be admitted, that this 
hypothesis receives no support from the experiments 
of Huber, who found that bees were insensible to 
the smell of oil of turpentine, which they particularly 
dislike, unless it was applied to the base of the trunk 
near the cavity of the mouth. But the experiments 
of Lehmann afforded opposite results, and Huber's 
abservations must therefore he considered inconclu- 
sive. Upon the whole, we have not sufficient grounds 
to come to any decision on the subject, although the 
probability is in favour of the tracheae being organs 
of smell as well as of respiration. 
The organs of sight are usually large and conspi- 
cuous, forming, as it were, the lateral portions of the 
cranium, sometimes meeting at their inner edges, and 
thus occupying greater part of the head. Owing to 
their structure, they have received the name of com- 
pound eyes , and they are often aided in their func- 
tions by another sort, in the form of small chrystalline 
points placed on the forehead, which are called sim- 
ple eyes , ocelli, or stemmata . When present, the 
latter are generally three in number, placed in the 
form of a triangle on the crown ; sometimes there are 
* There really does exist, notwithstanding Kirby and 
Spence’s assertion to the contrary, an internal membrane, al- 
though it is very thin and closely adherent to the spiral thread. 
