In one of the early lectures we discussed the protective and defensive colours of caterpillars in general, and those of caterpillars of the Sphingidæ in particular. I showed that those naked caterpillars which live on plants among the grass, or on the grass itself, are often not only green, like fresh grass-stalks, or yellowish-grey, like dry ones, but all the larger forms also exhibit light, usually white, longitudinal lines, which, by mimicking the sharp light reflections on the grass-stems, heighten the protective resemblance. We also spoke of the light transverse stripes, often marked with pink or lilac-blue, of many of the large green caterpillars which live on trees and bushes, and whose likeness to the leaves is heightened by this imitation of the lateral veining of a leaf; and finally we mentioned the warning coloration indicative of unpleasant or nauseous taste, among which must be classed not only vivid contrasts of colour, but also specially conspicuous elements of colour such as light ring-spots upon a dark ground. These different colour schemes which protect the caterpillars from their enemies are usually only to be found in the adolescent caterpillar, not in the very small one which has just emerged from the egg, and the development of the markings in the individual life clearly shows that the phylogeny of the markings is more or less obviously contained in the ontogeny. There are three different schemes of marking which occur in the caterpillars of hawk-moths or Sphingidæ--longitudinal striping, obliquely transverse striping, and spots. Longitudinal striping pure and unmixed is now found only in a few species, for instance in the caterpillar of the _Macroglossa stellatarum_ (Fig. 115), in which a white longitudinal line, beginning at the tip of the tail, runs up each side of the body to the head as a 'sub-dorsal stripe' (_sbd_). These, with other two similar stripes, effectively secure the fairly large caterpillar from discovery when it is among grass and herbs. [Illustration: FIG. 115. Caterpillar of the Humming bird Hawk-moth, _Macroglossa stellatarum_. _sbd_, the sub-dorsal line.] Transverse striping occurs as the sole mode of marking in species which live on bushes and trees whose leaves have strong lateral veins, such as willows, poplars, oaks, privet, syringa, and so on, and these markings associated with the leaf-green of their colouring protect them most effectively from discovery.