236 THE CANADIAN ENTOMOLOGIST. 



is roughened in some manner, as well as the portion of joint mentioned, 

 on the areas of friction. This mechanism cannot be properly explained 

 without a dissection, hence the insufficiency of the preceding. 



To stridulate, Ranatra holds the first pair of legs in the same plane 

 as the body, perfectly straight, and somewhat separated at the extremities, 

 in such a manner as to press the coxa; against the inner surface of the 

 outer wall of the coxal cavity. The insect jerks its legs while in this posi- 

 tion back and forth, and thus causes the vibration. Both legs may be in 

 motion at once, independently of each other ; or one only may be waved 

 about. Each leg, therefore, stridulates without reference to the other, as 

 Ranatra jerkily moves it about in anger or excitement. 



In the literature and references that I have been able to look up, no 

 mention is made of this peculiarity of Ranatra, although it cannot have 

 passed unnoticed by students of these hemipterous groups. In his '■^Cata- 

 logus synonimicus et topographicus Rhynchotorum aquatilium hucusque in 

 Italia repertorum," Dr. A. Griffini gives a very full bibliography of the 

 aquatic Rhynchota, and he records only one essay on the subject in 

 question, " On Stridulation in the Hemiptera Heteroptera," by O. H. 

 Swinton, which mentions A^epa, but makes no reference to Ranatra. Mr. 

 G. W. Kirkaldy, F.E.S., also has had a paper on "The Stridulating 

 Organs of Water Bugs (Rhynchota), especially of Corixidse," treating 

 principally of the last named. At some future date I shall endeavour to 

 give a fuller account of the organs in Ranatra, together with a bibli- 

 ography. Meantime, a few random notes on habits may not be without 

 interest. 



The way in which Ranatra seizes its prey is very characteristic. I 

 feed mine on living flies, which are presented with a forceps under water. 

 When the fly attracts its attention, Ranatra very slowly, almost imper- 

 ceptibly, moves its fore-legs, with the knife-like tarsus away from the tibia, 

 toward its prey. When the tibiae are almost, or quite, touching the victim, 

 the movement is so sudden and quick that one is aware of it only by see- 

 ing the prey seized. Sometimes its hold is not satisfactory, and then it 

 will let go, first with one tarsus, get a firmer grip with that, and then do 

 the same with the other. Once it has the fly securely held, Ranatra 

 slowly approaches it to its extended beak, with which it seems to touch 

 and feel it until it finds a suitable spot, and proceeds to a leisurely meal. 

 From this it might seem that Ranatra depends for its food not on such 

 inhabitants of the water as swim by, but on the unwary ones that come to 



