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Show 1873.] COLOURING IN INSECTS. 155 limits, the species presenting a corresponding range of variation in its disguising characters. In illustration of this class I m a y mention the " leaf-butterflies " (Kallimaparalekta and K. inachis), as also some of the true "leaf-insects" (Phasmidae). The objects here imitated are leaves in various stages of decay; and as these are of variable hues, the insects present varieties of corresponding shades of colour. III. Cases iii which the imitated object undergoes a change of character once during the lifetime of the individual, whose disguise changes in correspondence. In illustration of this class I will name the larvae of two of our native Geometrae, viz. Geometra papilionaria and Acidalia dege-neraria, the former of which is dull purplish before hibernation, but becomes green in the spring; while the latter, from the period of its emergence from the egg in July to the middle of September, is of a greenish-brown colour, but changes to a rusty brown at this period preparatory to hibernation *. It is obvious that a change of habit in the species entailing a new relationship with the environment is equivalent to a change of character in the environment itself. In this class therefore I include such larvae as those of Thecla betulee, the genera Smerinthus and Sphinx, Macaria alternata, & c , which are green when feeding on their respective food-plants, but become brown previous to pupation, at which period the insects require to crawl over the ground to find a suitable burying-place. IV. Cases in which the colour of the imitated object undergoes periodic change, the protective characters of the species changing in correspondence. This class includes those cases in which, like the Alpine Hare, the Ermine, and the Ptarmigan, the disguising characters change with the season. In concluding this classification I would call attention to the manner in which the characters of the imitated object and the disguising characters of the species vary together. The truth thus brought to light I hope to fully investigate in a future paper. Variable protective colouring. I have already had occasion to mention that there existed a certain number of cases that could not be included in any class of the above arrangement; it is to these residual instances that I would wish to direct the attention of naturalists in the present paper, as their study offers a wide and interesting field for observation. The particular class of cases that I propose to include under the term "variable protective colouring" will be best understood from the following examples which I have collected from various sources. First, with reference to insects in the larval state. Fabricius * See the recently published description of this larva by Mr. William Buckler, of Emsworth, ' Entom. Monthly Mag.' Oct. 1872, p. 115. A somewhat similar change of colour is recorded in the larva of Gnophos obscurata by Mr. Hellins, I. c. June 1871, p. 20. |