Thus it is not difficult to perceive how a whole group of genera could have made shift with this low grade of marking up to the present time. Colour and marking are not the only means of offence and defence possessed by these insects; and it is just such simply-marked larvæ as those of the _Macroglossinæ_ which have the protective habit of feeding only at night, and of concealing themselves by day. Moreover, under certain conditions of life the longitudinal stripes may be a better means of protection, even for a Sphinx-larva, than any other marking; and all those species in which this pattern is retained at the present time live either among grasses or on _Coniferæ_. It cannot be properly said that the second form of marking--the oblique stripes--has been developed out of the first. If these had arisen by the transformation of the longitudinal stripes, the two forms could not exist side by side. This is the case, however, both in certain species in the adult state (_Calymnia Panopus_[162]), as well as in others during their young stages (most beautifully seen in _Smerinthus Populi_, Fig. 56). Various facts tend to show that the oblique stripes appeared in the phyletic development _later_ than the longitudinal lines. In the first place they appear later than the latter in the ontogeny of certain species. This is the case with _Chærocampa Elpenor_ and _Porcellus_, in which, however, they certainly do not reach a high state of development. Then again, the longitudinal lines disappear completely in the course of the ontogeny, whilst the oblique stripes alone maintain their ground. Thus, the subdorsal line vanishes at a very early stage, with the exception of a small residue,[163] in all native species of _Smerinthus_. I have already attempted to show that new characters are only acquired _in the last stage_, and that if still newer ones are then added, the former disappear from the last stage, and are transferred back to a younger one. _Characters vanish therefore from a stage in the same order as they were acquired._ Finally, among the genera with longitudinal stripes (_e.g. Macroglossa_) we know certain species which, when at an advanced age, possess oblique stripes (_M. Fuciformis_), although these slant in a direction opposite to those of most of the other larvæ of the _Sphingidæ_. These are, however, always species which differ from their allies in their mode of life, not feeding on grasses or low plants, but on large-leaved shrubs. If we were able to ascertain the ontogeny of these species, we should find that the oblique stripes appeared late in life, as has already been shown in the case of _Pterogon Œnotheræ_.