With respect to the object of the music, Dr. Hartman in speaking of the _Cicada septemdecim_ of the United States, says,[450] “the drums are now (June 6th and 7th, 1851) heard in all directions. This I believe to be the marital summons from the males. Standing in thick chestnut sprouts about as high as my head, where hundreds were around me, I observed the females coming around the drumming males.” He adds, “this season (Aug. 1868) a dwarf pear-tree in my garden produced about fifty larvæ of _Cic. pruinosa_; and I several times noticed the females to alight near a male while he was uttering his clanging notes.” Fritz Müller writes to me from S. Brazil that he has often listened to a musical contest between two or three males of a Cicada, having a particularly loud voice, and seated at a considerable distance from each other. As soon as the first had finished his song, a second immediately began; and after he had concluded, another began, and so on. As there is so much rivalry between the males, it is probable that the females not only discover them by the sounds emitted, but that, like female birds, they are excited or allured by the male with the most attractive voice. I have not found any well-marked cases of ornamental differences between the sexes of the Homoptera. Mr. Douglas informs me that there are three British species, in which the male is black or marked with black bands, whilst the females are pale-coloured or obscure. Order, _Orthoptera_.—The males in the three saltatorial families belonging to this Order are remarkable for their musical powers, namely the Achetidæ or crickets, the Locustidæ for which there is no exact equivalent name in English, and the Acridiidæ or grasshoppers. The stridulation produced by some of the Locustidæ is so loud that it can be heard during the night at the distance of a mile;[451] and that made by certain species is not unmusical even to the human ear, so that the Indians on the Amazons keep them in wicker cages. All observers agree that the sounds serve either to call or excite the mute females. But it has been noticed[452] that the male migratory locust of Russia (one of the Acridiidæ) whilst coupled with the female, stridulates from anger or jealousy when approached by another male. The house-cricket when surprised at night uses its voice to warn its fellows.[453] In North America the Katy-did (_Platyphyllum concavum_, one of the Locustidæ) is described[454] as mounting on the upper branches of a tree, and in the evening beginning “his noisy babble, while rival notes issue from the neighbouring trees, and the groves resound with the call of _Katy-did-she-did_, the live-long night.” Mr. Bates, in speaking of the European field-cricket (one of the Achetidæ), says, “the male has been observed to place itself in the evening at the entrance of its burrow, and stridulate until a female approaches, when the louder notes are succeeded by a more subdued tone, whilst the successful musician