LIFE HISTORY. 47 



As would naturally be expected in the case of so small a creature, 

 the weight of a single worker is very small. To determine it, 1,000 

 workers, freshly captured and killed with cyanid fumes, were care- 

 fully counted and weighed on an analytical balance. The thousand 

 insects weighed 0.2077 gram, which gave the average weight of each 

 worker as 0.0002077 gram, or two-tenths of a milligram. 



As already stated, there is only one caste among the workers. In 

 a large colony there seems to be something of a division of labor, 

 certain ones engaging in foraging, others in nursing, and still others 

 in excavating or sanitary work. However, any individual worker 

 can assume the duties of any other, and does do so when exigencies 

 demand. Worker callows, barely hardened into mature adults, go 

 forth in search of food and the hardened veterans of many months' 

 service seem to make as efficient nurses as even the youngest. 



LENGTH OF LIFE. 



The workers are particularly long lived. A colony of about 70 

 workers was made queenless and broodless on July 8, 1908. By 

 October 10 the number of workers had become reduced to about 40, 

 and some of the origmal ones survived until February 25, 1909, a 

 period of 6^ months. As tliis colony was queenless, the workers in 

 it were not under normal conditions. With a queen present it is 

 ordinarily impossible to ascertain the length of life of individual 

 workers, owing to the constant maturing of young. However, in 

 one case we had opportunity to observe the survival of workers with 

 queen present and with immature stages absent. A colony started 

 on October 10, 1908, proved to have an infertile, dealated queen 

 and was kept under observation to see how long the workers would 

 survive. The last of these died on July 22, 1'909, having lived for 9 

 months and 12 days after their capture. Their age at the time they 

 were confined in the cage on October 10 was, of course, unknown; but 

 it appears safe to conclude that under normal conditions the workers 

 not infrequently live to an age of at least 10 or 12 months. 



Mr. G. D. Smith was successful in keeping a queen and several 

 workers for more than two months, during which time they had no 

 food other than that which may have been contained in the drinking 

 water furnished them. During this period of prolonged fasting the 

 queen even deposited eggs, some of which hatched into larvae. 



The Male. 



The appearance of the adult male is illustrated at a, figure 6. The 

 males average about 2.8 to 3 mm. in length. The most noticeable 

 feature about them is the manner in which the thorax is enormously 

 developed. The abdomen is relatively small and the head short 



