OF INSECTS. 185 



tion, other authors are inclined to place it in the 

 tracheae, either in their external margins or interior 

 I ramifications. Cuvier is of opinion that they are very 

 well calculated to perform the office, the internal 

 I 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 

 observations must therefore be 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. 



