In answer to my question as to whether the males of any species of butterfly or moth are known to pass a life of different length from that of the female, Dr. Speyer stated that he knew of no observations on this point. The following are the only instances of well-established direct observations upon single individuals, in my possession[12]:— _Pieris napi_, var. _bryoniae_ [male] and [female], captured on the wing: lived in confinement ten days, and were then killed. _Vanessa prorsa_ lived at most ten days in confinement. _Vanessa urticae_ lived ten to thirteen days in confinement. _Papilio ajax._ According to a letter from Mr. W. H. Edwards, the female, when she leaves the pupa, contains unripe eggs in her body, and lives for about six weeks—calculating from the first appearance of this butterfly to the disappearance of the same generation[13]. The males live longer, and continue to fly when very worn and exhausted. A worn female is very seldom seen;—‘I believe the female does not live long after laying her eggs, but this takes some days, and probably two weeks.’ _Lycaena violacea._ According to Mr. Edwards, the first brood of this species lives three to four weeks at the most. _Smerinthus tiliae._ A female, which had just emerged from the pupa, was caught on June 24th; on the 29th pairing took place; on the 1st of July she laid about eighty eggs, and died the following day. She lived nine days, taking no food during this period, and she only survived the deposition of eggs by a single day. _Macroglossa stellatarum._ A female, captured on the wing and already fertilized, lived in confinement from June 28th to July 4th. During this time she laid about eighty eggs, at intervals and singly; she then disappeared, and must have died, although the body could not be found among the grass at the bottom of the cage in which she was confined. _Saturnia pyri._ A pair which quitted the cocoons on the 24th or 25th of April, remained in coitu from the 26th until May 2nd—six or seven days; the female then laid a number of eggs, and died. _Psyche graminella._ The fertilized female lives some days, and the unfertilized female over a week (Speyer). _Solenobia triquetrella._ ‘The parthenogenetic form (I refer to the one which I have shown to be parthenogenetic in Oken’s ‘Isis,’ 1846, p. 30) lays a mass of eggs in the abandoned case, soon after emergence. The oviposition causes her body to shrivel up, and some hours afterwards she dies. The non-parthenogenetic female of the same species remains for many days, waiting to be fertilized; if this does not occur, she lives over a week.’ ‘The parthenogenetic female lives for hardly a day, and the same is true of the parthenogenetic females of another species of _Solenobia_’ (_S. inconspicuella_?). Letter from Dr. Speyer.