Mayer’s experiments with the large moth _Callosamia promethea_ furnish important information as to the factors involved in mating. The results are all the more significant from our present point of view because the colors of male and female are in this species markedly different. The wings of the male are black, those of the female reddish brown; the antennæ of the male are large and bushy, those of the female small and slender. Mayer found that the males are attracted by the female from some distance when the latter are put into a glass jar covered by only coarse mosquito-netting, but if the same jars are turned upside down the males are unable to find the female. Females concealed in loose cotton attracted males. Females were put into a box with an open chimney at one end, the other open end being covered by mosquito-netting. A current of air blew into the open end and out of the chimney. The males flew to the end of the chimney from which the air came and fluttered about in the neighborhood. Males are attracted to places where a female has been kept even several hours after her removal. The male finds the female through the sense-organs in his antennæ, for a male whose abdomen has been cut off and the sides of whose thorax are covered with shellac will still fly to the female, but if his antennæ he coated with any substance he no longer seeks the female. If the eyes of the males are blackened they will mate with females “in the normal manner.” Mayer cut off the wings of females and glued male wings in their places, so that the female looked like a male. Males readily mated with these females. The wings of males were cut off and female wings glued in their place. Mating occurred “with normal frequency, and I was unable to detect that the female displayed any unusual aversion” to such males. Males with female wings pass unnoticed by other males. In a later paper (1901) Mayer and Soule describe how, when the wings of the male were painted scarlet or green, the males were accepted as readily as normals in competition with them. Experiments were also made by them with the gipsy moth. Wingless males met with more “resistance” from the female than do normal males, but when the eyes were covered the wingless males succeeded as often as the normal males, but the number of observations on which this statement is were far too few to be of any value, and there are several other observations that make any such conclusion from the evidence highly uncertain.