That the antennæ are the organs by which this knowledge of coming events with regard to the weather is obtained by the insects, appears probable. They may, perhaps, perceive by their delicate surfaces, changes in the _electrical_ condition of the air, which are quite insensible to ourselves: and as all change of weather is preceded and accompanied by changes of electrical balance of one kind or another in the air, they may be thus forewarned of the coming danger. The following is the manoeuvre of a large number of insects of the beetle tribe. When they are about to move from any station where they have been at rest, the first thing they usually do before they move a step, is to bring forward and expand their antennæ, which have previously been folded up out of the way. They open them as widely as possible, so as to expose them to all the influences of the air, and then, if they be satisfied, they unfold their wings and take their flight. We might compare this proceeding with that of one of ourselves looking up at the direction of the wind, or tapping the weather-glass in the hall, previous to setting out for the day! Too much stress, however, it must be added, is not to be laid upon this point; for while it is unquestionable that insects have knowledge of the weather, it is of course very difficult to ascertain with certainty whether it is by means of their antennæ, or by the general feeling of their bodies; analogous, perhaps, to what rheumatic persons feel when the wind goes round to the _north-east_. There is a still more singular use of the antennæ, which deserves to be mentioned. These organs appear to be the principal instruments of _speech_, if we may use such a term, or, at any rate, of the communication of intelligence. When the soldier ants go out upon their expeditions, and have left the nest, previously to setting off, they touch each other with their antennæ and forehead on the trunk; and this is their signal for marching, for as soon as ever a soldier feels this tap, he immediately puts himself in motion. When, also, they have any discovery to communicate, they strike with them those that they meet, in a particularly impressive manner; and if a hungry ant wants to be fed, it touches with its two antennæ, moving them very rapidly, those of the individual from which it expects its meal. They appear to salute one another by gently tapping each other's antennæ, as we should shake hands on meeting an old friend!