HEARING IN MOSQUITOES 35 
Perhaps the most interesting result of his experiments was the discovery of 
the fact that the antennal hairs enable the mosquito to determine the direction 
from which the sound-waves proceed. He experimented with the song of the 
female and found that the hairs of the male antenne vibrate when the song of 
the female comes more or less at right angles to them, while those which point 
to or from the source of sound are not affected. If the song is directly in front 
of the head it will be most fully received by the antennal hairs. If the song of 
the female affects one antenna more than the other, the male, by turning until 
both antenne are equally affected, could thus determine the direction of the 
female. 
“The song of the female vibrates the fibrille of one of the antenne more 
forcibly than those of the other. The insect spreads the angle between his an- 
tenne, and thus, as I have observed, brings the fibrille, situate within the angle 
formed by the antenne, in a direction approximately parallel to the axis of the 
body. The mosquito now turns his body in the direction of that antenna whose 
fibrils are most affected, and thus gives greater intensity to the vibrations of the 
fibrils of the other antenna. When he has thus brought the vibrations of the 
antenne to equality of intensity, he has placed his body in the direction of the 
radiation of the sound, and he directs his flight accordingly ; and from my ex- 
periments it would appear that he can thus guide himself to within 5° of the 
direction of the female.” 
While Mayer accepted the function of the antenne as auditory, he clearly 
perceived that no comparison could be made with the sense of hearing in the 
higher vertebrates, and expresses his conclusions in these terms: 
“ Some may assume from the fact of the co-vibration of these fibrils to sounds 
of different pitch, that the mosquito has the power of decomposing the sensation 
of a composite sound into its simple components, as is done by the higher verte- 
brates ; but I do not hold this view, but believe that the range of co-vibration of 
the fibrils of the mosquito is to enable it to apprehend the varying pitch of the 
sounds of the female. In other words, the want of definite and fixed pitch to 
the female’s song demands for the receiving apparatus of her sounds a corre- 
sponding range of the co-vibration, so that instead of indicating a high order 
of auditory development it is really the lowest, except in its power of determining 
the direction of a sonorous centre, in which respect it surpasses by far our own 
ear.” 
Our own observations of the habits of mosquitoes lead us to doubt that the 
antenne, if auditory at all, are so in their primary function. The foregoing 
hypotheses are founded upon the assumption that the male seeks the female and 
is attracted by her song. In fact such is not the case. At least in those forms 
in which the antenne of the male are most highly specialized the males 
“swarm ” and the female seeks the male. In our experience the song of the 
female does not attract the male. Mayer appears to have come very near the 
truth when he found that the antennex served for orientation. One of us (Knab) 
has observed that the males in a swarm always dance facing the breeze or air- 
current, no matter how slight this may be, and adjust themselves instantly to 
any shifting of the breeze. Why this is done would be difficult to explain, but 
that the antennz make this possible is clearly apparent from Mayer’s observa- 
tions. Of course it can not be denied that the antenne are perhaps also, in a 
