184 JOUUXAL OF ECONOMIC ENTOMOLOGY [Vol. 2 



the connecting membranes distinctly visible. The writer has often 

 noticed workers returning from their attendance upon plant lice 

 with abdomens so distended that they looked like little drops of sil- 

 very liquid. Particularly is this appearance presented when the re- 

 turning workers are viewed with a strong light beyond them. 



As already stated there is but one caste among the workers. In a 

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

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

 excavating or sanitarj^ work. However, any individual worker can 

 assume the duties of any other and does do so when exigencies de- 

 mand. Worker callows, barely hardened into mature adults, go forth 

 in search of food and the hardened veterans of many months' ser- 

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



The workers are particularly long-lived. A colony of about seventy 

 workers was made ciueenless and broodless on July 8, 1908. By Oc- 

 tober 10th the number of workers had become reduced to about forty 

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

 period of 6I/2 months. But for the fact that many of these workers 

 met death accidentally a longer period of survival would doubtless 

 have been recorded. 



The Egg 



The egg, which is to produce a worker, is elliptical, about .2 mm. 

 wdde by .3 mm. long. It is pearly white, lustrous and without mark- 

 ings (See Plate 7, A). As time for hatching approaches it loses its 

 brilliancy and the surface takes on a duller appearance. This is not 

 sufficiently pronounced and uniform, however, to be taken as a 

 safe guide to immediate hatching. The egg membrane is exceedingly 

 thin, so thin in fact that when the embryo has taken on the larval 

 shape, the membrane not infrequently adapts itself in a way to the 

 general contour of the enclosed embryo, thus making it very difficult 

 to distinguish between eggs and just-hatched larvae. 



Some care of the egg by the workers seems essential to complete 

 embryonic development. Eggs deposited in test tubes by isolated 

 queens have gone through a portion of the embryonic development, 

 but we have not been successful in getting them to hatch. This may 

 be due in part to the ease with which the delicate embryos can be in- 

 jured in handling and to the fact that when placed on glass condens- 

 ing moisture may retard or stop development. 



Incubation 



The eggs, after deposition by the queen, hatch in from 18 to 55 

 days, according to the prevailing temperature. The longer periods 



