III.] LIFE AND DEATH. I 59 



the amount of nutriment at its disposal. Many other Lepidop- 

 tera, such as the majority of butterflies, fly about for weeks 

 depositing their eggs, but others, such as the emperor-moths 

 and lappet-moths, lay their eggs one after another and then die. 

 The eggs of the parthenogenetic Psychidae are laid directly 

 after the imago has left the cocoon, and death ensues im- 

 mediately, so that the whole life of the imago only lasts for a 

 few hours. No one could look upon this brief life as a primitive 

 arrangement among Lepidoptera, any more than we do upon 

 the absence of wings in the female Psychidae ; shortening of 

 life here is therefore clearly explicable. 



In such cases have we any right to speak of the fatal effect of 

 reproduction ? We may certainly say that these insects die of 

 exhaustion ; their vital strength is used up in the last effort of 

 laying eggs, and in the case of the males, in the act of copula- 

 tion. Reproduction is here certainly the most apparent cause 

 of death, but a more remote and deeper cause is to be found in 

 the limitation of vital strength to the length and the necessary 

 duties of the reproductive period. The fact that there are 

 female Lepidoptera which, like the emperor-moths, do not feed 

 in the imago-state, proves the truth of this statement. They 

 still possess a mouth and a complete alimentary canal, but they 

 have no spiral ' tongue,' and do not take food of any kind, not 

 even a drop of water. They live in a torpid condition for days 

 or weeks until fertilization is accomplished, and then they lay 

 their eggs and die. The habit of extracting honey from flowers 

 — common to most hawk-moths and butterflies — would not have 

 thus fallen into disuse, if the store of nutriment, accumulated in 

 the form of the fat-bodies, during the life of the caterpillar, had 

 not been exactly sufficient to maintain life until the completion 

 of oviposition. The fact that the habit of taking food has been 

 thus abandoned is a proof that the duration of life beyond 

 the reproductive period would not be to the advantage of the 

 species. 



The protraction of existence into old age among the higher 

 Metazoa proves that death is not a necessary consequence of 

 reproduction. It seems to me that Gotte's statement ' that the 

 appearances of senility must not be regarded as the general 

 cause of death' is not in opposition to my opinions but rather 

 to those which receive general acceptance. I have myself 



