594 THE SENSES AND SENSORY ORGANS. 
Duponchel [262a] regarded the antenne as hygroscopic 
organs; but Rath [183] says there is no proof of any such 
function. Watery vapour has many of the physical properties 
of odorous bodies, more especially in its relations with radiant 
energy (Tyndall). It is, however, clear that it could not excite 
the olfactory membrane of Vertebrates, since this is always 
surrounded by air, saturated with aqueous vapour, and is itself 
moist. The end organs of an insect’s antennz are, however, 
placed under very different conditions. That they can act as 
hygroscopic bodies in the physical sense is extremely im- 
probable, since the hypodermis would certainly prevent their 
ever becoming dry enough to absorb moisture like a dried 
vegetable or animal fibre; but there is no reason why the 
nerve end organs should not be stimulated by a moist atmo- 
sphere. 
It has long been argued that Bees and other Hymenoptera 
discover the approach of rain by the hygroscopic condition of 
the atmosphere; and I have made a series of careful observations 
on the House Cricket (Acheta domestica). It is well known 
that these insects drink with avidity, and cannot live long with- 
out asupply of water. I have repeatedly kept Crickets under a 
glass shade for months, supplying them with food and water. 
When the supply of water is withdrawn for two or three days, 
even in winter, and for a less time in summer, these insects 
become very thirsty. I introduce a supply of water in a watch- 
glass, concealed in a cardboard tray, so that it cannot be seen 
by the insect. The antenna are at once raised, the insect 
runs about and soon finds the water, always seeking it by sway- 
ing its antenna. As soon as these organs are brought near 
the water, the insect goes straight to it. Crickets which have 
been freshly captured, and kept a day or two without water, 
find it almost directly ; and I have observed in cold weather 
that they first seek it close to the glass bell, where the vapour 
condenses most rapidly, but in a few minutes or less go straight 
to the water. The manner in which the antenne are moved 
and the rapidity with which the insects find the water imme- 
diately after the tips of the antennz come vertically over the 
