256 H. L. SHANTZ. 



points have developed, one on either side (PI. X., 4). These 

 bristles now develop alternately until all are formed ; the con- 

 striction between the appendage and the abdomen does not ap- 

 pear until the appendage is almost mature (PI. X., 5, 6). 



B. coloradensis was collected in Dead Lake, a small body of 

 water in the Pike's Peak region. This lake has already been 

 described in some detail by Ward (1904: 131, 135, PI. XXIX., 

 XXIV., XXV). Without visible outlet or inlet, it lies on the 

 divide between Ruxton Creek and Beaver Creek at an altitude 

 of about 3,350 m. (11,000 feet U. S. Topographic Map). On 

 the southeast side is the ridge leading to the summit of Bald 

 Mountain. This ridge is covered with a dense coniferous forest, 

 shading the lake during the morning. The lake measures about 

 100 m. by 75m. and does not exceed 2 m. in depth. The forest 

 barely touches the southeast shore. The remainder of the shore 

 is a mountain meadow, with a few shrubs here and there, and 

 numerous large boulders lying in and about the lake. The bot- 

 tom of the lake is of blue clay, probably derived from the de- 

 composition of the granite, which is the only rock of this region. 

 It has the appearance of an old lake, one about to disappear 

 (Ward, 1904 : 132). There is very little change of level, and 

 the lake is not known to have been dry. For the last 14 years 

 during which time the writer has repeatedly visited this place, 

 conditions have not changed in any marked degree. During the 

 summer of 1904 a sawmill and air pump were operated on the 

 shore, without affecting the life in any marked degree. The 

 water is clear, pure and very slightly alkaline. On July 12, 

 1904, one drop of dilute H 2 SO 4 in which I cc. = 50.954 mg., was 

 sufficient to neutralize loocc. of lake water, with methyl orange 

 used as an indicator. 



The earliest collections were made on May 20, 1904, the day 

 when the ice broke, and while the southeast side was still parti- 

 ally covered with ice. The temperature of the water was 4. 7 

 C. in the warmest places, and varied to almost o C. in the cold- 

 est. Many larvae had appeared, among which were those of B. 

 coloradensis. These varied in stages of development from those 

 in which only the antennae, mandibular legs, and unsegmented 

 body could be seen, to those in which all the segments had been . 

 formed. 



