IS THE VALVE OF UTR1CULARIA SENSITIVE? 161 



larva into the utricle. And this is the fact with all of 

 the species of utricularia that I have experimented 

 with, except in the case of U. purpurea. In this spe- 

 cies the valve does not seem to be so sensitive as in the 

 others. A slight brush of the tail of a mosquito larva 

 does not cause the valve to open ; it takes a more vigor- 

 ous blow with the head ; hence in this species the mos- 

 quito larva is almost always caught head first. 



I have a number of alcoholic specimens of the mos- 

 quito larvae with only the head caught in the valve ; 

 the larva had grown too large to admit the first joint 

 of the body through .the orifice. Many of these speci- 

 mens 1 put in alcohol while the larvas were still living ; 

 others I observed until they were dead. With the head 

 only caught in the valve, and the rest of the body stick- 

 ing out, it was left free to thrash about, and it seemed 

 the more the victim struggled, the closer the valve fit- 

 ted about the head. A half-grown mosquito larva thus 

 caught could sway the utricle from side to side, and 

 make considerable demonstration that could be seen 

 with the unassisted eye, but I never saw one escape. 



Even here Mr. Darwin's argument would hardly hold 

 good — that the head serves as a wedge — for the valve 

 opens just as quickly as in the other species when the 

 blow is hard enough, and the mosquito larva never goes 

 poking about using its head as a wedge. But the chi- 

 ronomus larva not only swims and wriggles, but it uses 

 its brush -like feet, and crawls along the leaves and 

 stems of the plants, and often feeds on the hairs" or 



a 



