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Show 266 MR. E. B. POULTON ON THE PROTECTIVE [Mar. 1, suggests that the enemies are startled by the sudden 'manner which the bright colours are displayed ; but I am not aware that a similar significance has ever been attributed to the bright colours of Butterflies suddenly seen when the wings are opened. The former suggestion probably holds, for I think tbe margin of the underwings is more commonly found to be notched than any other part of these insects when captured. But the primary significance of such bright colours, concealed in the protective attitude of rest, must be the same as those of Butterflies, and I should attribute the same meaning -of sexual adornment-to the brilliant colours of the underwings of the Grasshoppers of the genus CEdipoda, also alluded to by Jenner Weir (see Trans. Ent. Soc. Lond. 1869, pt. i. p. 23). CONCLUSIONS. The following are the general conclusions arrived at by the of the experimental data tabulated in this paper :- 1. The extremely specialized defence of the larval stage follows from its delicate anatomical construction and the necessities which are imposed on it as the great feeding-stage. 2. Highly conspicuous insects nearly always possess some unpleasant attribute, i. e. a disagreeable taste or smell in the tissues and fluids of the body, or (in the case of the smell) discharged from special glands ; irritating hairs ; or stings. 3. The conspicuous appearance may be due to strongly-contrasted colours, the presence of hairs or tufts, and the attitude in which the body is held, and to gregarious habits, or attention may be attracted by violent movements which take place when an enemy appears. 4. In a small number of cases a highly conspicuous appearance has not yet been shown to be attended by any unpleasant attribute. 5. In the various species in which a conspicuous appearance is produced by colour and marking, the same colours and patterns appear again and again repeated. In this way the Vertebrate enemies are only compelled to learn a few types of appearance, and the types themselves are of a kind which such enemies most easily learn. Furthermore certain appearances are especially impressed on the vertebrate foes by highly aggressive insects, feared because of stings &c. ; and hence there is especial advantage in any approximation to such types. Again, the selected type of conspicuous appearance also depends on the (probably protective) colours which existed at the time when the conspicuous appearance first commenced (these can be determined with a great degree of probability in some few cases). 6. In a relatively few cases aggressive forms among the Vertebrata (Serpents) are mimicked, although such an appearance is pure intimidation, for the insect is quite harmless. 7. It is not uncommon for an insect to be protectively coloured but when detected to assume a terrifying attitude, and in some cases to take up offensive measures (discharge of irritating fluid, &c). |
