The study of the geographical distribution of Insects acquires additional interest by its connection with astronomical calculations, and with geological researches. From them it is understood that the earth was once covered with snow and ice from the poles to the tropics, and that the like event may recur in the future, and restore the hemispheres generally to the freshness and newness which they possessed at the close of the glacial period. The beginning of the cessation of this period corresponds with the origin of the present distribution of insect life, or with the commencement of the ascent of the individuals from the tropics towards the poles.