The Structure and Special Physiology of Insects 29 
Fig. 56.—Male mosquito, 
showing (a.h.) antennal 
hairs. (After Jordan 
and Kellogg; three times 
natural size.) 
distances soon found their way to the jar (containing females) which had 
its mouth open to the air, but no male came to the jar with its mouth her¬ 
metically sealed. Through the glass sides of both 
jars the females were plainly visible. The antennae 
of certain males were covered with shellac. These 
males, when released, never found the females, and 
often paid no attention to them when brought within 
an inch of their bodies. Of other males the eyes 
were covered with pitch; but these males had no 
difficulty whatever in finding the females. It is 
plainly obvious from these experiments that the 
males found the females wholly by scent and not at 
all by sight. 
That some insects hear is proved by their posses¬ 
sion of auditory organs, and has also been demon¬ 
strated by experiment. The fact, too, that many 
insects have special sound-making apparatus and 
do make characteristic sounds is a kind of proof 
that they can also hear. The auditory organs of insects, curiously enough, 
are of several kinds and are situated on different parts of the body, in 
various species. Among the locusts, 
katydids, and crickets, the most con¬ 
spicuous of all the sound-making in¬ 
sects except the cicada, the ears are 
small tympanic membranes on the 
base of the abdomen in the locusts 
(Fig. 55), and on the tibiae of the fore 
legs in the katydids and crickets. 
Associated with each tympanum is a 
small liquid-filled vesicle and a special 
auditory ganglion from which an 
auditory nerve runs to one of the 
ganglia of the thorax. Among the 
Fig. 57.— Diagram of longitudinal section midges and mosquitoes the antennae— 
through first and second antennal seg- those all-important sensitive structures 
lormis, male, showing complex auditory — are abundantly provided with cer- 
organ composed of fine chitinous rods, tain fine long hairs, the auditory hairs 
(After 56), which take up the sound¬ 
waves and transmit the vibrations to an 
elaborate percipient structure composed of many fine chitin-rods and ganglion- 
ated nerves contained in the next to basal antennal segment (Fig. 57). From 
this segment runs a principal auditory nerve to the brain. Many other insects 
nerve-fibers, and nerve-cells. 
Child; greatly magnified.) 
