June, 1911.] Severin-Severin: Habits of Belostoma and Nepa. 105 



liquid material from the caudal end of the abdomen. Occasionally 

 an individual will do the same thing when taken suddenly out of the 

 aquarium. For a long time we were under the impression that water 

 had accumulated beneath the wings and that this was forcibly ejected 

 in some way. Recently a Lethocerus americannm was suddenly taken 

 out of the water and it also spurted forth a stream of liquid, which 

 happened to strike the nose of one of us and, from the peculiar odor, 

 we concluded that the ejection of the stream is due to a forcible 

 discharge of the contents of the rectum. 



A number of experiments were performed in order to determine 

 the length of time Belostoma and Ranatra can remain alive below 

 the surface of the water. Ten specimens of Belostoma fliiniincinn, 

 ten Ranatra aniericana and ten R. kirkaldyi were placed in a cage 

 (7Xi'^X5 inches) made of wire gauze and this was then com- 

 pletely emersed in water so that it was two inches below the surface- 

 film. The temperature of the water was 20° C. and of the atmos- 

 phere 23° C. In these experiments it was found that Belostoma 

 and the two species of Ranatra died, on an average, within twelve 

 hours. This result, however, would probably vary with the general 

 activity of the aquatic bugs and the temperature of the water, since 

 in the winter time, when the water is coated with ice, Belostomas and 

 Ranatras are unable to come to the surface of the water to get a 

 fresh supply of air. 



If Nepas are allowed to remain in a jar of water, containing no 

 vegetation or anything upon which they can crawl to the surface, 

 they will all sooner or later be drowned. We have kept Nepas alive 

 three months in a flat dish with water in it, shallow enough for the 

 insects to reach the surface with their breathing tube, by feeding 

 them now and then with house-flies and dragon-fly nymphs. 



Methods of Progression. — Packard (35, p. 158), Kirkaldy (28, p. 

 344 and 29, p. 154), Bueno (9, p. 53 and 12, pp. 1-4) and Brimley (i, 

 p. 88) have all discussed the method of progression of various 

 aquatic-bugs, and Bueno (12, pp. 2-3) has made a detailed study of 

 the method of swimming in Belostoma fliimineum. 



While Belostoma can swim with exceeding rapidity, Nepa makes 

 but slow progress in water. Belostoma, Lethocerus, Benacns, Nepa 

 and Ranatra alternate the movements of the hind pair of legs with 



