2176 Insects. 



the various objects with which they come in contact. But others rather avoid touching 

 any object with their antennae ; and not a few, as the dragon-flies, from the minute- 

 ness and position of these organs, could not well apply them to such a use. Many 

 Coleoptera seem to take very little notice if their antennas are touched, which certainly 

 does not seem to indicate them to be the chief seat of feeling. Neither is the struc- 

 ture of the antennae amongst the nocturnal Lepidoptera, the gnats, and some of the 

 Cerambycidae, suitable for this purpose. All these considerations would lead us to 

 reject the view that the antennas were universally and primarily organs of touch. It 

 is, however, very possible that in some species they may have this function in a 

 secondary manner, just as in the Pachydermata the nose, although retaining its ordi- 

 nary functions, becomes also the organ of touch. It remains, then, for us to decide 

 whether the antennae be the seat of smell or of hearing ; and the question naturally 

 arises,— to what extent do insects possess these senses ? 



The sense of hearing is chiefly calculated to mediate intercourse amongst animals 

 of the same species, and is mostly accompanied by a corresponding development of 

 the voice. The majority of insects are mute and solitary, and we have little direct 

 evidence to show whether they are capable of hearing or not. Various experiments 

 have been undertaken to decide the question, but the results have frequently been du- 

 bious and even contradictory. In some species, as in Blaps mortisaga, in the Cicadas 

 and several Orthoptera, the sense is undoubtedly present, though we have little know- 

 ledge of its degree of perfection. The sense of smell is of primary importance to 

 most animals, especially in the pursuit and selection-of their food, where it seems pre- 

 eminently supplimentary to the eye : it is, besides, frequently the principal medium 

 by which they examine and recognize objects of whatever kind. Thus the dog, the 

 cat, the horse, generally smell at any new or unknown body, and seem by that means 

 to get a satisfactory idea of its nature. Amongst insects this sense exists in great 

 perfection. With what unerring certainty will the ant or the wasp make their way to 

 anything sweet, however carefully concealed ! The Necrophaga and Geotrupidae 

 may often be seen flying along in a right line to those substances upon which they 

 prey, even when totally hid from view. And to what other sense can we attribute the 

 dexterity with which the parasitical Hymenoptera will detect their destined victim, 

 however carefully covered up from view ? The varied and powerful scents which many 

 insects emit render it very probable that they may seek out those of their own species, 

 pursue their prey, or be warned of the approach of an enemy by this sense. Almost 

 all the carnivorous Coleoptera emit a very powerful odour, especially Calosoma syco- 

 phanta, many of the Staphylinidae, the Necrophaga, several species of Meloe, Cantha- 

 ris, &c, and in other orders the same property occurs to a greater or less extent. This 

 certainly tends to support the view that the sense of smell must be well developed 

 amongst insects. 



If we turn to examine the comparative development of the antennae in different 

 insects, we shall generally find it most complete where the greatest accuracy of smell 

 may be observed or inferred, and vice versd. The senses of sight and smell are, to a 

 certain extent, capable of replacing each other as regards the pursuit of food. Some 

 animals hunt by scent, others by the eye, and the development of the organs is gene- 

 rally proportionate, with the apparent exception that the eyes of nocturnal animals are 

 mostly large, to take in as much light as possible : but for all this it is manifest that 

 they require an acute scent, and this we find to be the case. The dragon-fly hunts by 

 sight alone ; its swift motions and the prodigious development of the eye render scent 



