42 



THE ARGENTINE ANT. 



Table III. — Duration of larval stage of the Argentine ant at different seasons — 



worker. 



• Average day.s, 31.4. 



THE PUPA. 



When the pupal stage is reached by the young ant all doubt is 

 removed as to the sex of the individual, for one can tell at a glance 

 which pupae will transform into adult workers, which to males, and 

 which to queens. The pupas of these three forms are easily distin- 

 guishable and will be discussed in the order named. 



THE WORKER PUPA. 



(PI. IV, B, D.) 



The worker pupa immediately after transformation from the larval 

 stage is pure white, without markings, except that the compound eves 

 are promment as jet-black spots upon the head. The pupa is 

 slightly larger than the grown larva, the average length being about 

 2 mm. The head is by far the most prominent portion. A pupa 

 measuring 2.04 mm. in length was found to Jiave a head 1.19 mm. in 

 length (dorso-ventral diameter), while the thorax and abdomen 

 measured 0.51 and 0.561 mm., respectively. 



As time for transformation to adult apjH'oaches t]ie pupa changes to 

 a creamy color, then tJirough a light brown to a dark brown, the latter 

 shade being almost as dark as the body color of mature workers. The 

 time of these clianges varies with the duration of the pupal stage, but 

 the following record of changes in color of a pupa which occupied a 

 full 20 days from larva to adult (callow), is near the average: 



First to seventeenth day — Pupa pure white, except compound eyes. 

 Eighteenth day — Turned to a light creamy yellow. 

 Nineteenth day — Became a light brown. 

 Twentieth day — The brown color deepened. 

 Twenty-first day — Reached teneral stage. 



