308 
The Senses of the Lower Animals . 
i July. 
possess the sense of smell in a degree of perfection quite 
unknown to vertebrate animals, the question follows, What 
is its organ ? Here there is a want of accord among author- 
ities who have made this subject their study. Still we hold 
that a preponderating body of evidence points to the antennae 
as the seat of this sense. These organs occupy a situation 
exceedingly appropriate for the purpose ; they are exposed 
to currents of air, and can be readily applied to or held over 
any substance which the insect may wish to examine more 
closely, and they are most abundantly supplied with nerve- 
fibre. In flies the third or terminal joint receives thousands 
of such filaments, each apparently terminating in a small 
open cell. In some of the Buprestidae the antennae display 
multitudes of pores or open cells, scattered uniformly over 
the entire surface, whilst in others they are concentrated 
in a small depression upon each joint. The development of 
the antennae, which varies greatly in different groups, pre- 
sents, in the main, the features which we should expedt in 
an organ of scent. We know that in insedts — as indeed in 
all animals — the male seeks out the female, who in most 
cases is more sedentary in her habits, and is in some in- 
stances even devoid of wings. Hence we may fairly con- 
clude that the male will require to possess the sense of 
smell in a higher degree than the female. This is accord- 
ingly the invariable rule : if the antennae of the two sexes 
are not absolutely alike, those of the male are more highly 
developed. This is especially the case in such moths as are 
usually entrapped by the process of “ sembling,” as above 
mentioned. In these, as for instance in Saturnia Carp ini, 
the antennae of the female have the form of a bristle, while 
those of the male have a series of minute plates, like the 
barbs of a feather, projedting out on both sides, and exposing 
a great amount of surface to the air. 
We should also expedt the organs of smell to be more 
complicated in species which feed on a very narrow range of 
substances, and have consequently more difficulty in finding 
support than in omnivorous species whose food is every- 
where. We should also suppose that a less delicate sense 
of smell, and consequently a less highly developed organ, 
would be necessary in insedts possessing great locomotive 
powers than in such as travel slowly and awkwardly. Fur- 
ther, if the antennae are the organs of smell, their develop- 
ment should be to some extent inversely as that of the eye, 
and should be relatively higher in nodturnal than in diurnal 
species. All these suppositions may, generally speaking, be 
pronounced to agree with observed fadts. The dragonfly, 
