38 



THE CANADIAN ENTOMOLOGIST 



On turning over numerous flat stones I found the pupae of 

 this species {Hydroporus septentrionalis Gyll.) rather abundant in 

 some places. They were found abundant under stones lying on 

 soft, damp, fine sand overlying the broad flat rock-bed now above 

 the water. These were abundant on August 7, 1913, when I dis- 

 covered this insect, and I at first despaired of finding the larvae, 

 but on turning over numerous stones I was soon rewarded by 

 finding all stages, larvae, pupae and adults. The larvae construct 

 rather peculiar pupal chambers. These pupal chambers consist of 

 the fine, damp sand, lying over the red sandstone rock which forms 

 the river channel, built into peculiar mounds, usually with a small 

 opening at the top. These mounds are turret-shaped, measuring 

 0-7 mm. wide at the base, 5-6 mm. high, with an apical diameter 

 of about 2.5 mm. One of these is shown on pi. 1, fig. 2. They 

 are rather beautiful, and when abundant, as they often are under 



Fig. 9. — Hydroporus Septentrionalis, larval structures. 



flat rocks, they present, grouped thus together, the appearance 

 of a miniature mud village (pi. 1, fig. 4). I was fortunate enough 

 to observe through the opening in the top one of the larva con- 

 struct part of its domicile. Round and round it moved within, 

 gradually deepening, and at the same time widening, the interior 

 of the future pupal home. It would turn over and over, smooth- 

 ing out the sides. I did not observe the beginning of any of 

 these, pupal chambers, but I presume the larva began at first to 



