Whether display, such as birds appear to delight in ever takes place among the Lepidoptera seems doubtful Nevertheless, something closely akin thereto seems to have been found in the case of certain species of Butterflies (_Heliconius melpomene_ and _H. rhea_), which have been seen dancing in the air like gnats, and when some of them withdrew others took their places. Again, having regard to the fact that birds, when alarmed or excited, will perform the display which is more or less characteristic of periods of sexual excitement, it is possible that the position of alarm assumed by some of the Hawk Moths may also be used in Courtship (Fig. 1, Plate 31). But we have no evidence on this point, and from the part played by scent in the mating of Butterflies it seems improbable that such displays take place. A serious attempt to test the Sexual Selection theory by experiment—to test the extent, if any, of female choice in mating—was made some years ago by Mayer, an American naturalist, on the large Bombycid Moth (_Callosamia promethea_). This species exhibits striking dissimilarity between the sexes in regard to colour and pattern. “The females,” remarks Professor Kellog, “are reddish brown in ground colour, while the males are blackish, and in the two sexes the pattern is distinctly different....” Mayer took four hundred and forty-nine pupæ, in cocoons, of this moth and endeavoured to discover, first of all, whether the males found the females by sight or smell. Enclosing females in jars, some of which were covered and some of which were uncovered, he found that males paid no attention to females enclosed in transparent jars so closed as to prevent the escape of odours, while such as were enclosed in boxes or wrapped in cotton-wool, so as to be invisible, but yet capable of exhaling odour, were besieged by males. To locate the organs of scent in the female he cut off the abdomen of several and placed the abdomens and their late owners at some distance apart. Males came to the abdomens and not to the thorax and wings. Males whose antennæ were covered with shellac, photographic paste, glue, paraffin, etc., showed no response to the female exhalations, until the covering medium was removed.