April, '09] 



JOURNAL OF ECONOMIC ENTOMOLOGY 



187 



The duration of the larval period has been determined by observa- 

 tion in the artificial nests in the same manner as the incubation pe- 

 riod, already described. 



The following table shows the duration of the larval period at dif- 

 ferent seasons: 



TABLE II 

 Duration op Larval Stage at Different Seasons— Worker 



The Pupa 



The pupa immediately after transformation from the larval stage 

 is pure white, without markings, except that the compound eyes are 

 prominent as jet black spots upon the head. The pupa is slightly 

 larger than the grown larva, the average length being about 2 ram. 

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

 2.04 mm. in length was found to have a head 1.19 mm. in length 

 (dorso-ventral diameter) while the thorax and abdomen measured 

 .51 and .561 mm. respectively. The pupas are shown in Plate 7, 

 h and d. 



As time for transformation to adult approaches the pupa changes 

 to a creamy color, then through a light brown to a dark brown, the 

 latter shade being practically identical mth the body color of mature 

 workers. The time of these changes varies with the duration of the 

 pupal stage, but the following record of changes in color of a pupa 

 which occupied a full twenty days from larva to adult (callow), is 

 near the average : 



'We have not attempted to give the accumulated effective temperature neces- 

 sary for the development of different stages, as we are not satisfied as to 

 the critical point from which it should be computed. It is doubtless higher 

 than 43° F. 



