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Show 156 MR. R. MELDOLA ON VARIABLE PROTECTIVE [Feb. 4, long ago observed that the larva of Bryophila algae varied in colour according to the nature of its food-plant, being yellow when feeding on Lichen juniperinus, and grey when on L. saxatilis. Dr. Moller in 1867 published a paper containing a great number of observations on the influence exerted by external conditions upon insects*. Two of these, which belong actually to our present class, I will here quote. The ground-colour of the larva of Cucullia tanaceti is white when this insect is feeding on the leaves of the mugwort (Artemisia vulgaris) or tansy (Tanacetum vulgare), but changes to a yellow when it confines itself to the flowers of the latter. The larva of Chesias spartiata is stated by Koch to present two varieties-one of a green colour, that feeds on the leaves of broom (Spartium scopa-rium), and another of a yellow colour, that feeds on the flowers of that plant. This observation has been subsequently confirmed by Mr. William Buckler *j\ The larva of Cleora lichenaria, which is well known to be a wonderful case of adaptation to the lichen on which it feeds, is stated by Dr. Knaggs X to vary in depth of colour according as it occurs on light- or dark-coloured lichen. Many polyphagous caterpillars of the genus Eupithecia tend to assume the colour of the flower on which they are feeding: this is particularly to be observed in E. absynthiata ; and, in a recently published description of the larva of E. pimpinellata, which feeds on the seeds of Pimpinella magna and P. saxifraga, it is stated that " the colour of the larva seems to assimilate with the seeds-green ones upon green unripe seeds, and the red ones upon the purple ripe seeds" §. I have likewise observed a similar tendency in the larva of Mamestra persicariee to partake of the tint of the leaf on which it was feeding. The experiments of Mr. T. W . Wood || and others seem to establish the fact that under certain conditions the pupae of Lepidoptera tend to assume the colour of the surface on which the larva made its final change. Mr. Wood has observed, for instance, that a pupa of Vanessa polychloros was coloured like a dead leaf when among foliage, while a specimen from a wall was mottled grey. I have observed a similar fact with respect to the pupae of Synchloe bras-sicee and S. rapce, specimens from a black fence being generally darker than those found on walls. The particular conditions under which this photographic sensitiveness is acquired have not yet been fully investigated ; but such a tendency in a state of nature cannot but act beneficially towards the species by affording concealment ; I therefore propose to include such cases in the class now under consideration. With reference to insects in the perfect state, I am informed by Mr. F. Bond that Gnophos obscurata tends to vary in its ground- * Die Abhangigkeit der Insecten von ihrer TTmgebung. t Entom. Monthly Mag. April 1871, p. 261. \ Lepidopterist's Guide, new ed. p. 47. § Mr. William Prost in ' Newman's Entomologist,' Nov. 1872, p. 241. || Proc. Ent. Soc. of Lond. 1867, p. xcix. |