i88s.] 
Sense of Smell in Insects. 
269 
groups which we brought forward in speaking of locomotive 
power. In the dragonflies, and in the true flies, or Muscidse, 
the eyes are as remarkable for their size and efficiency as 
are the antennae for their minuteness and simplicity of 
structure. 
To show the higher development of the antennae in terres- 
trial than in aquatic groups, we need merely compare the 
Dytiscidae with the Carabidae, both similar in their diet and 
in their rapacious character. 
Let us now ask ourselves what meaning underlies these 
structural differences in various forms? We cannot look 
upon the antennae as mere ornamental appendages, like the 
crests, trains, and tufts met with in so many birds. Their 
ample supply of nerves characterises them at once as organs 
having some important function to fulfil. We glance first 
at their higher development in the mature inseCt than in the 
larva, and in the male as compared with the female of the 
same species. We know that of all the senses that of 
smell is most closely connected with sexual relations. Even 
in the human species it is comparatively in abeyance until 
the age of puberty. The indifference of young children to 
odours, pleasant or offensive, has often been noticed. It is 
by this sense in most animal species that the two sexes are 
attracted to each other ; and as it is almost invariably the 
part of the male to take the initiative and seek up the 
female, he requires the more powerful and sensitive olfactory 
organs. If we take those genera of nocturnal Lepidoptera 
above mentioned, such as Saturnia, &c., where the antennae 
of the male are so much more complicated than those of the 
female, we shall find two important points : — 
a. The male is aCtive in habit and possesses developed 
wings, whilst the female is in all cases sluggish and 
sedentary, often remaining at or near the spot where 
she has issued from the pupa. In many cases she is 
even practically wingless. 
b. The male actually does follow the female by scent. 
This is proved by a host of observations made by 
inseCt-hunters in the practice of sembling. Male 
moths will come from a considerable distance straight 
to a virgin female enclosed in a box. To controvert 
the plea that such males are attracted by some sound 
supposed to be emitted by the female, but inaudible to 
human ears, it has been found that they will hover over 
and settle on any objeCt upon which a virgin female 
has been sitting, or the empty cocoon from which she 
