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 original ones survived until February 25, 1909, a 
period of 6 J months. As this 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, 1909, 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 
