180 THE UNIVERSITY SCIENCE BULLETIN. 



adult at all, but is more akin to that of Corixa, and the entire form of the 

 insect in these stages is very different from that of the adult." 



The above was written in 1897. Little more has been added since that 

 time, due to the difficulty of keeping the nymphs alive under laboratory 

 conditions. Bueno, 1905, reported his failure to get them beyond the 

 second or third instar. 



Hoppe, 1912, in his paper on "Die Atmung von Notonecta glauca," 

 makes a few remarks on the life history, noting five nymphal instars. 



The writer, 1917, published an account of the biology of Notonecta 

 undulata, and during the year 1917 was able to study the biology of three 

 other species, N. variabilis, N. insulata, and N. irorata, which are found 

 in the waters about Ithaca, N. Y. The experience gained in studying 

 the behavior of N. undulata was found useful in bringing these species 

 through their transformations. 



The behavior of the back-swimmers, especially with reference to 

 respiration, has been quite fully treated, though even here there are 

 problems as yet unsolved. 



Brocher, 1909 and 1913, and Hoppe, 1912, have made extended studies 

 on the respiration of N. glauca and Christine Essenberg, 1915, of Berke- 

 ley, Cal., has written upon the behavior of four California species. 



ECOLOGY. 



The members of this genus have been made the object of an ecological 

 study by Bueno, who presented his notes in his "Notonecta of North 

 America." He says in substance that N. undulata hangs from the sur- 

 face almost constantly and its raptorial claws can be seen forming little 

 elevations as it hangs head down. N. insulata seems to prefer to float in 

 clear spaces in clear cold pools, about midway between the bottom and 

 surface. "On the other hand, N. irrorata and N. uhleri appear to like to 

 hide among the roots of plants growing at the water's edge, to which 

 they cling. The former may at other times also be seen floating below 

 the surface, in the shadow cast by bank or fallen tree or broken branch. 

 The habits of N. variabilis differ somewhat from the others, since this 

 bug prefers to lurk among the water weeds at the bottom." 



Oviposition. Until recently there seemed to be a distinction between 

 the manner of oviposition of the common European species and our 

 American forms, the common glauca of Europe placing its eggs in the 

 tisues of plants, as noted by Regembart in 1875, and our American 

 species affixing them to the surface of plants, as noted by Bueno and 

 Essenberg. The writer reviewed the question in the "Egg-laying habits 

 of Buenoa margaritacea" at which time he supposed all American species 

 placed their eggs upon the plants. In a footnote to his paper recording 

 the "Life History of Notonecta undulata," he recorded the fact that N. 

 irrorata places her eggs in plant tissues even better than N. glauca. In 

 another paper appearing in the Entomological News "Concerning the 

 oviposition of Notonectae," the writer presented the evidence as to the 

 manner of oviposition of the various members of the genus, basing this 

 evidence upon the study of the female ovipositors. The plates submitted 

 with this paper are here reproduced to indicate the interesting study 



