HOUSEHOLD INSECTS 253 



this stage varies from eleven to sixty-one days, the average 

 being about thirty-one days. In the pupal stage workers, 

 males, and queens can be readily distinguished. The 

 worker pupse are, at first, almost pure white, except for 

 two prominent jet black spots on the head the compound 

 eyes. Towards the end of this stage, which averages 

 about fifteen days, the colour changes through cream and 

 light brown to quite dark brown. The male pupa, which 

 is half as large again as the worker pupa, is also white at 

 first and passes through various colour changes to very 

 dark brown. This stage lasts, usually, about twenty-three 

 days, and, when the time for transformation to the adult 

 male arrives, the workers render every assistance in the 

 shedding of the pupal skin. The queen pupa is much 

 larger than the male pupa and more than twice as large 

 as the worker pupa, and, apart from its size, may be 

 readily recognised by the presence of prominent wing 

 pads. Colour-changes from white to brown take place, 

 but the duration of the stage is not known exactly, 

 though it is probably about four weeks. 



In the artificial formicaries, in which the ants were kept 

 under observation, no queens appeared. By analogy with 

 the honey bees, whose queens arise from eggs apparently 

 similar to those producing the workers, the development 

 taking place during the larval stage, owing to special food 

 provided by the workers, it is possible that the workers, 

 kept in confinement, could not obtain the requisite material 

 from which to elaborate the food necessary for rearing 

 queens. In all three forms, during the last few hours of 

 the pupal stage, the workers are busily engaged in assist- 

 ing in the transformation, being employed, for the most 

 part, in attempting to straighten out the legs and antennae. 

 The newly emerged ants are almost colourless and of feeble 

 gait, they are then known as " callows " ; quickly, however, 

 their colour deepens and they become indistinguishable 

 from the adults, but in the meantime the workers are 



