The Biology of Ageing in Insects 263 



Summary 



Queenless, Italian golden worker honey-bees, Apis mellifera, 

 maintained indoors on an excess of honey, pollen and water, 

 lived to a maximum of about 9 • 5 weeks ; in a second study of 

 over 4,000 bees a similar maximum value of ten weeks was 

 obtained. A maximum longevity of 7 • 5 weeks was found for 

 over 2,700 bees, properly marked and returned to the hive to 

 perform normal hive activities. As a criterion of old age, the 

 number of brain cells at two distinct levels of the adult honey- 

 bee brain was found to be virtually identical for both indoor and 

 outdoor (hive) senescent bees. 



In a study of over 8,500 houseflies, Musca domestica, of the 

 NAIDM strain, females were found to have a mean longevity 

 of 29 days and males a mean longevity of 17 days. Curves for 

 probit-log time plots indicated a relatively simple mortality 

 factor for the male population but a complex of several 

 mortality factors for the female cohort. Female longevity 

 was enhanced by the inclusion of powdered whole milk in the 

 adult diet of sugar and water. No such beneficial effect was 

 obtained for male houseflies. A study of the role of parental 

 age at the time of oviposition indicated a possible adverse 

 effect on the longevity of female offspring from oldest parents ; 

 for males reared from eggs from oldest parents there appears 

 to be an enhancement of the mean longevity, probably by a 

 selection of long-livedness through the old surviving female 

 parents. 



Acknowledgements 



Figs, la and lb were drawn by Miss Mary Lorenc. 



Fig. 3 was drawn by Mr. Rudolph Cavalcante. 



The author is deeply appreciative of the assistance of Dr. Albert S. 

 Perry of the USPHS Technical Development Laboratories, Savannah, 

 Georgia, for generously supplying the pupae of the NAIDM strain from 

 which this colony has been developed. 



The kind assistance of Miss Gertrude Uhr, Secretary of the Depart- 

 ment of Physiology, and Mrs. Elaine S. Rockstein, in the preparation of 

 the manuscript, is acknowledged. 



