THE CANADIAN ENTOMOLOGIST. 337 



NOTES ON HYDROPHILUS TRIANGULARIS SAY* 



BY ROBERT MATHESON, PH. D., ITHACA, N. Y. 



Although much study has been given to the European species 

 piceus and much has been written of its life-history, anatomy and 

 metamorphosis, scarcely anything has been published concerning 

 the American species triangularis Say. Since the brief account given 

 by H. Garman in the American Naturalist in 1881 I find but few 

 references to this species in American literature. As this is one of 

 our largest beetles, and is commonly met with in aquatic collect- 

 ing, I hope this short account gathered from a brief :-tudy during 

 the summer of 1912 may be of use to others working in this group. 



The beetles undoubtedly hibernate and egg-laying occurs early 

 in June. Garman found the egg-cases about the first of June at 

 Normal, 111., and in one case the female was in the act of finishing 

 her case. I found the completed egg-cases at Ithaca on June 

 24 and 26. These egg-cases are peculiar and interesting struc- 

 tures. Although Garman has given a good description of the 

 nidus, it may be worth while to redescribe it, as his paper is now 

 inaccessible to the average worker in entomology. 



The egg-case (pi. XXII, fig. 2) is always attached to pieces of 



floating leaves, bits of weeds, etc., and never, as far as I know, to 



living plants. The case with the projecting horn-like mast floats 



gracefully on the surface of the water. The cases must be sought 



with considerable care, as they are not easily recognized among the 



floating debris. I have found them most commonly in shallow 



pools with abundant vegetation and rich in insect life (PI. XXII, 



fig. 1.) The leaf to which it is usually attached serves as a float and 



aids in keeping the mast erect and above the surface of the water. 



The case is smooth, brownish in colour, the upper surface closely 



adhering to its support (PI. XXII, fig. 2.) It measures about 22 



mm. wide, 24 mm. long and 15 mm. deep. The horn-like process is 



usually about 7-8 mm. long, and projects from the front of the 



case almost at right angles to the upper surface. It is dense, hard 



and almost black in colour, composed of closely-woven strands of 



silk. Below it expands into a broad hatchet-shaped plate, as seen 



in figure 2. It is supposed that t his horn, which is really a very 



*Contribution from the Entomological Laboratory of Cornell University. 

 October, 1914. 



