294 



SCIENCE 



[N. S. Vol. XLV. No. 1160 



India, which was probably its original home, to 

 Egypt about a dozen years ago in cotton seed. 

 The Department of Agriculture has under- 

 taken strenuous measiu:es to prevent the in- 

 troduction of the pink boll worm from Mexico. 

 The introduction of cotton seed and of baled 

 cotton which often carries scattered seeds has 

 been prohibited, and Congress has made a spe- 

 cial appropriation under which very thorough 

 work in enforcing quarantine measures can be 

 done on the Texas border. 



It is interesting to note the recent experi- 

 ence of Brazil with the pink boll worm. In 

 1913 the Brazilian government paid consider- 

 able attention to the encouragement of the 

 culture of Egyptian cotton in that country. 

 An agent was sent to Egypt and large quan- 

 tities of seed were shipped to Brazil. This 

 seed was distributed throughout the republic 

 by a branch of the Ministry of Agriculture. 

 This branch has inspectors in every state 

 capital. Each one of these received quantities 

 of the seed and distributed it free to all appli- 

 cants. A more thorough method of dissemina- 

 tion of an insect in a new country could 

 hardly be devised. Early in 1914 a careful 

 survey of the cotton belt of Brazil was made 

 by an American who was engaged in the en- 

 couragement of cotton culture in the republic. 

 He found no indications of the cotton boll 

 weevil for which he was looking especially or 

 of any other insect pest attacking the seed or 

 bolls. Late in 1916 he made another trip over 

 the same territory and found that the pink 

 boll worm was generally and thoroughly estab- 

 lished. In fact the pest was so numerous that 

 the yields of certain fields were reduced by 

 half. ISTaturally the situation attracted great 

 attention and many suggestions were made 

 about relief measures. Some of the legis- 

 lators suggested the passage of a law compell- 

 ing the burning of all cotton fields in Brazil. 

 Of course it is too late to stamp out the insect 

 by any such means, but the whole episode em- 

 phasizes enormously the importance of quar- 

 antine measures to prevent the introduction of 

 pests which in all probability can never be 

 exterminated when they have once become 

 established. W. D. Hunter 



Bdkeati of Entomology 



SPECIAL ARTICLES 



THE EFFECT OF RETARDATION OF GROWTH 



UPON THE BREEDING PERIOD AND 



DURATION OF LIFE 



OF RATS' 



During the course of our experiments on 

 nutrition we have had a number of rats which 

 were stunted for various periods of time. With 

 respect to these animals the question has fre- 

 quently been raised as to whether this retarda- 

 tion of growth tended to prolong their life be- 

 yond the average span ; that is, whether physio- 

 logical age is a function of time alone or also 

 of growth. The inquiry then becomes perti- 

 nent as to what may be considered the average 

 length of Hfe of a rat. 



Donaldson^ states that " a rat three years 

 old may be regarded as corresponding to a 

 man ninety years old." Slonaker^ has reported 

 that one of Ms rats reached an age of 45 

 months ; and recently one of our rats, although 

 fed on a uniform experimental diet since it 

 was 6 weeks old, reached the age of 40 months 

 — the longest life yet recorded for our colony. 

 In an attempt to find out how long our rats 

 might be expected to live, we have at various 

 times set aside a number of stock rats to be 

 kept under our ordinary laboratory conditions 

 during their entire lifetime. Out of 91 such 

 animals, 17 (19 per cent.) died under one year 

 of age; 48 (53 per cent.) died between one and 

 two years of age; and 26 (29 per cent.) lived 

 more than two years, the oldest one reaching 

 an age of nearly 34 months. From these fig- 

 ures it is evident that less than a third of the 

 rats in our colony may be expected to live to be 

 more than two years old. 



Considering the wide variations in the ages 

 of these rats it was thought that possibly a 

 more definite, although an indirect answer to 

 the question of the effect of stunting upon the 

 leng-th of life might be obtained by determin- 

 ing the age to which stunted females remain 



1 The expenses of this investigation were shared 

 by the Connecticut Agricultural Experiment Sta- 

 tion and the Carnegie Institution of Washington, 

 D. C. 



2 Donaldson, H. H., ''The Eat," Memoirs of the 

 Wistar Institute, No. 6, Philadelphia, 1915. - 



3 Slonaker, J. E., /. Animal Behavior, 1912, II., 

 20. 



