LIFE HISTORY OF HYDROUS ( HYDROPHILUS) TRIANGULARIS. 



23 



The pupa is snow white throughout when first transformed, but the eyes begin 

 to darken in a very short time, and then the various appendages, including the legs 

 and wing pads, and finally the body itself, the color assumed being a reddish brown. 

 Of a dozen pup^ obtained by the present author all were white when taken from the 

 pupal chamber except one that transformed within 10 or 15 minutes. Four of them 

 remained white on preservation, indicating that they had been formed but a short 



Fig. 16.— Ventral view of pupa. Fig. 18.— The posterior cerci 



of the pupa. 



time. The others turned to various shades of reddish brown within 24 hours, the 

 depth of shade probably varying with the length of time that had elapsed since pu- 

 pation. Two of them became dark brown over the entire surface, approaching 

 black in the eyes, the maxillary palps, the tarsi of the legs, and the last two joints of 

 the abdomen. In one pupa this color was communicated even to the bases of the 

 cerci and the large anterior spines. If the pupa is undisturbed in the darkness of 

 the pupal chamber, it probably remains white until the pupa skin begins to separate 



