As these ant utterances are not sufficiently loud to be audible to our human ears, they must, I suppose, be inferred from the existence of the organs above-mentioned, and the way in which they work; but this is surely sufficient data to go upon, since it is hardly possible for one hard substance to grate upon another silently. Forel, accordingly, as well as Janet and other observers, now believe sound to be one of the principal means by which ants hold converse with each other, and it is interesting to find that Grassi and Sandias have arrived at the same conclusion in regard to white ants, or termites. Their opinion, together with the facts upon which it has been founded, is thus expressed:— “Several writers have mentioned the convulsive movements characteristic of Termites. These movements, or quiverings, are easily observed in Calotermes, and may be repeated periodically at very short intervals, almost at the frequency of the pulse-rate. In the act of quivering, the legs are held motionless, whilst the body is shaken forwards and backwards. Sometimes a white ant may stop, whilst running, in order to quiver one or more times. Occasionally these convulsive movements are repeated a few times only, and then stop altogether; but at other times they recur after a few seconds’ or, at most, a few minutes’ rest, and may thus be continued, sometimes, for hours, at regular or irregular intervals. In the intervals between successive convulsions the insect remains still, or progresses for a short distance only. These movements are executed by all members of the colony except the newly hatched ones. I have satisfied myself,” continues Professor Grassi, “by careful observation of the phenomena exhibited in tube-nests, that these convulsions serve as a cry to summon help or give alarm, or as a lament: in short as a mode of intercommunication.”[9]