

Vol. XLVI. LONDON, FEBRUARY, 1914 No. 2 



LIFE-HISTORY OF A DYTISCID BEETLE (HYDROPORUS 

 SEPTENTRIONALIS GYLL.).* 



BY ROBERT MATHESON, ITHACA, N. Y. 



The Salmon River, a small stream which flows close by the 

 Nova Scotia Agricultural College, Truro, N. S., harbours many 

 interesting species of aquatic insects. At this point it flows 

 through a red sandstone region, the high, red rocky walls stand- 

 ing out in clear relief against a green background of grassy turf and 

 coniferous trees (pl.l, fig.l). During midsummer the river becomes 

 a small stream trickling lazily over its pebbled bottom, leaving wide 

 stretches of flat red rocks covered with fine sand. Here abound 

 mayflies, stoneflies and numerous small water beetles, besides 

 many others. Along the sandy banks tiger-beetles are abundant, 

 and numerous heads are seen to appear and disappear as one 

 walks slowly along. I was interested in trying to rear some of 

 the more common Dytiscid beetles, but found it a difficult task 

 after procuring the larvae to provide the proper conditions in order 

 to secure continued larval development, pupation, and finally the 

 coveted adult. 



While collecting one day last summer (August 7, 1913), I was 

 delighted to find on turning over some flat rocks several beautiful 

 white pupoe quietly resting on their backs in rather wonderfully 

 constructed pupal chambers. Furthermore, there were several 

 different, not only species, but families represented, no't all, how- 

 ever, in such peculiar pupal chambers. I was not long in finding 

 representatives of the Carabidse, Dytiscidae, Hydrophilidae and 

 Parnidce, oftentimes all under the same large flat stone. Unfor- 

 tunately, other pressing work did not give me opportunity to make 

 as full notes on ?s many of the species as I could wish. However, 

 there is one interesting form, the life-history of which, in part at 

 least, I wish to present in this short paper. 



This species was kindly determined for rm by Mr. John D. Sherman, Jr. 



