TECHNICAL NOTE.--For an appreciation of the reality of protective resemblances observations must be made in the field. Examples are easily found. Locusts, katydids, green caterpillars, lizards, crouching rabbits, and brooding birds are readily observed instances of general protective resemblance. For examples of variable resemblance examine specimens of a single locust species taken from different localities; the individuals of the various species of the genus _Trimerotropis_ show much variation to harmonize with their surroundings. Collect a number of larvæ (caterpillars) of one of the swallow-tail butterflies (_Papilio_), and when ready to pupate put them separately into pasteboard boxes lined inside with differently colored paper. The chrysalids will show in their coloration the influence of the different colors of the lining paper, their immediate environment. As examples of special protective resemblance observe inch- or span-worms (larvæ of Geometrid moths). The walking-stick is not uncommon; many spiders that inhabit flower-cups show striking protective color patterns; and the Graptas or comma-butterflies which resemble dead leaves may be examined. To illustrate warning colors, find, if possible, the larvæ (caterpillars) of the common milkweed or monarch butterfly (_Anosia plexippus_), and offer them to birds, at the same time offering other caterpillars, and note the results. For terrifying or threatening appearance find specimens of the large green tobacco- or tomato-worm (larva of the five-spotted sphinx-moth, _Phlegethontius carolina_), or other sphingid larvæ. The butterflies illustrating the striking example of mimicry, described on p. 432, can be found in most parts of the country. Syrphid and other flies which mimic bees and wasps can readily be found on flowers. Each student should search for himself for examples of protective resemblance.