Insects. 2177 



almost unnecessary ; and here accordingly we find the antennae small and compara- 

 tively simple. The Necrophorus, on the other hand, which seeks its food, as far as we 

 can perceive, by scent alone, and which cannot flit up and down with the celerity and 

 ease of the dragon-fly, has large clavate antennas. Tn the nocturnal insects, where the 

 eyes, though large, are frequently insufficient, we find, for the most part, large and 

 complicated antennas, as in Saturnia and Melolontha. Omnivorous insects do not re- 

 quire so powerful, or rather so delicate a scent, as those which are confined to one or 

 two substances for food. Thus we see the antennas of the Carabici, of the Staphyli- 

 nidas, of the common fly, comparatively simple ; promiscuous in their feeding, they 

 are in little danger of famine. Very few, if any, of the Curculionidas and Lamelli- 

 cornes are omnivorous : most of the former are limited to some particular plant, whilst 

 the latter, whether preying, like the Geotrupidas, on animal refuse, or, like the Melo- 

 lonthidas, on leaves, or, like the Cetoniadae, on flowers and the sap of trees, are equally 

 select in their feeding. 



The antennas of male insects are usually more highly developed than those of fe- 

 males ; and this also affords a good argument in favour of their being olfactory organs. 

 The males usually go in search of the females, whilst the latter remain concealed in 

 trees and bushes, in some genera entirely apterous, and in all impeded in motion by 

 the greater bulk of the abdomen. This difference in the habits of the sexes is in many 

 species so marked, that the females are rarely taken whilst the males are abundant. 

 The next question is, what sense guides the male to his partner in the midst of her 

 concealment ? A stratagem successfully employed in capturing several nocturnal 

 Lepidoptera seems to throw much light on the subject. If an unimpregnated female 

 Saturnia be placed in a box, and carried out to some suitable place, males of the same 

 species will come, often from a considerable distance, and alight upon the box. This 

 cannot surely be referred to sight or hearing, or to any other sense with which we are 

 acquainted, except smell, especially when we call to mind that an impregnated female 

 has no such influence. Here, then, the male requires this sense in greater perfection 

 than does the female, and the development of the antennas perfectly agrees with this 

 supposition. The antennas of the larva are small and rudimentary, but attain full 

 development simultaneously with the generative organs. Amongst higher animals 

 we find the sense of smell remaining in like manner imperfect, until the age of ma- 

 turity, as is especially the case in man. If the antennas were the organs of hearing, 

 we might naturally expect to find them most highly developed in those insects pro- 

 vided with a voice ; but this is not the case. If we observe an insect in search of 

 food, we shall find that its antennas appear excited, and when a suitable substance is 

 found they are held near it, or sometimes made to touch it. Now we can understand 

 an animal smelling its food, but why should it listen to it ? Offer honey to a Lucanus 

 cervus (the size and — if I may so speak — the docility of this insect make it very pro- 

 per for such experiments), and you will almost always see the leaves of his antennas 

 expand. Some naturalists have observed that insects move their antennas if alarmed 

 by a sudden noise, and have hence supposed this organ to be the seat of hearing. 

 Such a conclusion is gratuitous : a man under similar circumstances may move his 

 arms or legs in a convulsive manner, yet this does not prove them to be the organs of 

 hearing. These considerations, I should submit, render it probable that the antennas 

 are the organs of smell or of some sense closely analogous. 



J. W. Slater. 



