HUNGERFORD: AQUATIC HEMIPTERA. 159 



the bottom. Bueno says R. quadridentata frequents deep water, where 

 it clings quite fast to the stems of rushes or grasses, with its air tube 

 piercing the surface film. The writer has found this common enough 

 in pools where weeds had lodged, and also upon the floating dead leaves 

 and stalks of cattail, where they were basking in the sun and entirely dry. 

 Hibernation. Bueno says that Ranatra winters as an adult and is 

 sometimes found frozen in ponds. Marshall and Severin, 1904, note that 

 they were found in mud at the bottom of pools or creeks in winter. This 

 seems as good a place as any to record the splendid observations of 

 Wessenberg-Lund "Uber die Respirationsverhaltnisse bei unter dem Eise 

 uber winternden, luftatmenden Wasserinsekten, besonders der Wasser- 

 kafer und Wasserwanzen (1910-'ll)." There is an English summary at 

 the end of this interesting paper which is here quoted: 



"It is a well-known fact, that air-breathing insects, especially Dytiscidse, 

 Hydroplnlidse and waterbugs hibernate beneath the ice. For several 

 months these animals which, as far as we know, do not possess any other 

 organ of respiration than the open metapneustic tracheal system, though 

 totally excluded from the air, sustain life in the ice-covered lakes. Ob- 

 servations through the ice as well as in ponds, from which the ice had 

 been removed, show that the animals do not, like frogs, bury themselves 

 in the mud, but at any rate, during the first winter months, are swimming 

 about lively beneath the ice. 



"Now, it has been shown that water insects especially in the fall at 

 night-fall, disappear from ponds with slight vegetation, where they often 

 made their home in summer and have laid their eggs, now going in search 

 of localities with rich vegetation, more especiallj'^ bubbling springs or 

 ponds, where the beach is covered with green plants. Numerous observa- 

 tions in nature further show that the green plants, especially during the 

 first winter months, produce great quantities of oxygen. Like silvery 

 bubbles the oxygen covers the plants and later on accumulates beneath 

 the ice. According to experiments in the laboratory and observations in 

 nature it may be supposed that this oxygen during the first part of the 

 winter forms the respiration air of the animals. Later on, when the 

 vegetation dies off, the production of oxygen decreases, and methane and 

 carbonic acid accumulates beneath the ice, the bubbles will not suffice to 

 meet the claims of respiration. In what manner then are the animals able 

 to sustain life beneath the ice during the two or three last winter months? 

 The present paper shows, that insects, which in summer die, when only for 

 a few minutes or hours excluded from the air, in winter at a temperature 

 near zero are quite able for months to support a total exclusion from air. 

 When every possibility of getting air fit for breathing is excluded, it 

 seems that the animals settle down in a winter sleep, or 'Kaltestarre,' in 

 which respiration is extremely lowered. In our country this winter sleep 

 principally takes place in the Fontinalis carpets, which cover the bottom 

 of a great many ponds and small lakes. It has been supposed that 

 respiration through the integument plays a much greater part than 

 hitherto believed. It has been emphasized that the views and supposi- 

 tions set forth in this paper should be subject to thorough experimental 

 explorations in physiological laboratories." 



He saw an adult Ranatra swim under 3 cm. of ice; noted that other 

 bugs also do this and also that the large fat bodies and small eggs coni- 

 moniy noted in the fall are reversed in the spring. 



Mating. Bueno says that in mating the male is below and to one side 

 of the female. The process as noted by the writer is a prolonged one. 

 The sexes may be distinguished by the figures on plate XVIII. 



