Seven species only of the larger moths have any blue; of these, four are hairy, the other three are Hawk-moths.  In one, the Death’s Head, the violet color of the side stripes certainly renders the insect less conspicuous among the flowers of the potato, on which it feeds.  In the Oleander Hawk-moth there are two blue patches, which, both in color and form, curiously resemble the petals of the periwinkle, on which it feeds.  In the third species, the small Elephant Hawk-moth, the bluish spots form the centres of the above-mentioned eye-like spots.

In one family, as already mentioned, the caterpillars are very often brown, and closely resemble bits of stick, the similarity being much increased by the peculiar attitudes they assume.  On the other hand, the large brown caterpillars of certain Hawk-moths are night feeders, concealing themselves on the ground by day; and it is remarkable that while those species, such as the Convolvulus Hawk-moth, which feed on low plants, turn brown as they increase in age and size, others, which frequent trees, and cannot therefore descend to the ground for concealment, remain green throughout life.  Omitting these, there are among the larger species, seventeen which are brown, of which twelve are hairy, and two have extensile caudal filaments.  The others closely resemble bits of stick, and place themselves in peculiar and stiff attitudes.

And thus, summing up the caterpillars, both of butterflies and moths, out of eighty-eight spiny and hairy species, only one is green, and even this may not be protectively colored, since it has conspicuous yellow warts.  On the other hand, a very great majority of the black and brown caterpillars, as well as those more or less marked with blue and red, are either hairy or spiny, or have some special protection.

Here, then, I think we see reasons, for many at any rate, of the variations of color and markings in caterpillars, which at first sight seem so fantastic and inexplicable.  I should, however, produce an impression very different from that which I wish to convey, were I to lead you to suppose that all these varieties have been explained, or are understood.  Far from it; they still offer a large field for study; nevertheless, I venture to think the evidence now brought forward, however imperfectly, is at least sufficient to justify the conclusion that there is not a hair or a line, not a spot or a color, for which there is not a reason—­which has not a purpose or a meaning in the economy of nature.

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PROTECTIVE RESEMBLANCES IN SPIDERS

BY ELIZABETH G. PECKHAM.[10]

[10] Abbreviated from the occasional Papers of the Natural History Society of Wisconsin, Vol.  I., 1889.  By permission.

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There are, among spiders, two forms of protective modification:  the first, including all cases of protective resemblance to vegetable and inorganic things—­that is, all modifications of color or of color and form that tend to make them inconspicuous in their natural relations—­I shall call direct protection.  The second form, which I shall call indirect protection, includes two classes, the spiders which are specially protected themselves and those which mimic other creatures which are specially protected.