The Distribution of Senescence 



capable of living on their intake and stores for ten years, while 

 the mole cricket has been thought able to live much longer. 

 Activity reduces the life-span: Camboue (1926) greatly pro- 

 longed the life of butterflies by decapitating them. 



The influence of reproduction on life-span is equally variable, 

 but it often seems to involve inroads upon stored and irreplace- 

 able reserves. Unmated females of Periplaneta lay fewer eggs 

 than mated females and live longer (Griffiths and Tauber, 

 1942). The life-span in both male and female Drosophila is sub- 

 stantially decreased by mating (Bilewicz 1953). Krumbiegel 



% 

 100 



SO 



60 



kO 



20 



7 



8 



II 12 



Fig. 26. — Survival curves of 145 isolated virgin females (I) and 44 isolated, 

 fertilized females (II) of the moth Fumea crassiorella (from Matthes, 1951). 



found that the reserves in the fat-body of Carabids decreases 

 after first copulation, but increases again with feeding (1929). 

 In the moth Fumea crassiorella Matthes (1951) found that the 

 longevity of the female was halved by copulation if egg-laying 

 was allowed, and slightly reduced by it if egg-laying was 

 prevented (Fig. 26). 



The theory of 'cerebral death' (Gehirntod) in insects arises 

 chiefly from some long-standing work on bees. Hodge (1894, 

 1895), Pixell-Goodrich (1920) and Schmidt (1923) all described 

 cerebral degeneration, reduction of cerebral cell-number, and 

 disorganization of the nervous system as characteristic and 

 probably causal mechanisms in the senescence of worker bees. 

 h 99 



