THE HABITS OF NOTONECTIDAE 383 



the animal is suspended by the surface film, it begins to move 

 its forelegs. Hoppe suggests that by moving the legs the insect 

 forces the air into the spiracles in the thorax. I am rather 

 inclined to believe that it is trying to straighten out the hairs 

 and to brush away the impurities, because the animal performs 

 these movements every time some foreign substance is dropped 

 on the thorax. If a small particle of asphalt be placed on the 

 thorax, the animal moves the legs in an effort to free itself from 

 it, and if it can reach the part, will also use the beak for the 

 same purpose. It brushes the ventral and dorsal surfaces of 

 the abdomen with the hind legs, and especially the tip and 

 lateral margins. 



Notonecta, if sealed in water, dies within from three to five 

 hours. In this case it hangs to the surface film all the time 

 with its body covered with gas bubbles. If a drop of oil is 

 put on the ventral surface of its body, the creature dies imme- 

 diately. If the backswimmer is sealed in the water from which 

 the oxygen has been expelled by boiling, death results in from 

 five to ten minutes. If the water is left exposed to the air, the 

 insect clings to the surface film almost constantly, with the 

 fringes lifted and the breathing pores exposed, while under 

 ordinary circumstances it comes to the surface only once in 

 every thirty or forty minutes. On a dry substratum, if exposed 

 to sunshine, the insect dies within forty or fifty minutes; in a 

 cool and shady place it can live much longer. 



In several books on insects the statement is made that Noto- 

 nectidae bury their eggs in the stems of plants. I have found 

 that this is not the case in any one of the species studied. The 

 ova are usually deposited and glued on sticks or on the stems 

 of plants. Very often I have found the eggs deposited on the 

 backs of other insects, such as dragonfly larvae, and on the 

 walls of the aquarium. Soft sticks were placed in the aquarium. 

 The eggs, however, were never found buried in the stems, but 

 were always deposited in rows around the sticks. In the pro- 

 cess of ovoposition, the female attaches herself to the lower 

 surface of the stick and moves the posterior segments very 

 vigorously until the egg is extruded and attached, then she 

 moves away. Frequently embryos are found in a row with 

 their heads pointing in the same direction. If the eggs are 

 examined immediately after they have been deposited, the sur- 



