Very little information exists as to the life-history of the Aptera; as for their food, it is generally considered to consist of refuse vegetable or animal matter. It is usual to say that they are completely destitute of metamorphosis, but Templeton says of _Lepisma niveo-fasciata_ that "the young differ so much from the mature Insect that I took them at first for a distinct species; the thoracic plates are proportionately less broad, and the first is devoid of the white marginal band." As regards the moults, it would appear that in this, as in so many other points, great diversity prevails, Grassi stating that in _Campodea_ there is a single fragmentary casting of the skin; and Sommer informing us that in _Macrotoma plumbea_ the moults are not only numerous, but continue, after the creature has attained its full growth, throughout life. A very marked feature of the Aptera is their intolerance of a dry atmosphere. Although _Campodea_ can exist under very diverse conditions, it dies very soon after being placed in a dry closed tube; and the same susceptibility appears to be shared by all the other members of the Order, though it is not so extreme in all; possibly it may be due to some peculiarity in the structure {196}of the integument. So far as tolerance of heat and cold goes, the Aptera can apparently exist in any climate, for though some of the species extend to the Arctic regions, others are peculiar to the tropics. _Thysanura_ are recorded by Klebs and Scudder as occurring commonly in amber; the latter author has described a fossil, supposed to be a _Lepisma_, found in the Tertiary deposits at Florissant. Scudder has also described another fossil, likewise from Florissant, which he considers to form a special sub-order of Thysanura—_Ballostoma_—but it is extremely doubtful whether this anomalous creature should be assigned to the Order at all. A still older fossil, _Dasyleptus lucasii_ Brongniart, from the Carboniferous strata in France, is considered to belong to the Order Aptera, but it must be admitted there is some doubt on this point.