OBSERVATIONS ON INSECT LIFE 169 



they are no match. Thanks to their nimbleness the 

 water-boatmen are secure from attack. The only 

 creature that I have seen successful in capturing them 

 has been the water-scorpion, Nepa, and it succeeds by 

 its stealth rather than by skill. It lies in ambush until 

 a boatman comes between its wide-opened anterior 

 legs furnished with strong blades. Then suddenly 

 the blades come sharp together and the boatman is 

 secured. 



The Notonectidce are predaceous in their habits. 

 They capture the small insects that tumble into the 

 pool. One peculiarity in their mode of feeding 

 interested me. Anybody, who has carefully watched 

 these water-bugs, must have noticed that at intervals 

 they swim down into the water and maintain them- 

 selves absolutely stationary some little distance 

 beneath the surface by very rapid vibrations of their 

 hind limbs, specially modified for the purpose of 

 swimming. I could not understand the significance 

 of this habit until I saw the boatmen dealing with 

 their insect prey. I noticed that, immediately after 

 capturing an insect on the surface, the boatman would 

 descend with its victim and literally hover beneath the 

 water with its struggling capture until the insect was 

 drowned. I therefore conclude that this habit of 

 repeated submergence has been developed by the 

 boatmen to enable them to drown their insect prey. 



The boatmen do not confine their attacks to the 

 smallest insects, as their powers of swimming are 

 sufficiently strong for a single insect to drag beneath 

 the water and drown a beetle six or eight times its 

 own size. They are cannibals, not only eating their 

 own dead comrades, but attacking them when 



