1911.] 



249 



The next tliiu<i;- to be done was to trace the beetle to its real fooJ-plaiit, 

 and this proved an unexpectedly easy matter. Wading into the stream, 

 I pulled up a few plants and immediately found the cocoons attached 

 to the stems, near the roots, of Potamogeton ijectinatus. They have 

 also occurred on an aqiiatic species of Banuncnlnt^. The lai-vae are 

 decidedly gregarious, feeding at the roots of these plants in the mud at 

 the bottom of the stream, sometimes six or eight of them occurring to- 

 gether in various stages, ranging from a quite small size up to full 

 growth. From the cocoons brought home by me, two specimens of the 

 beetle have emerged, one of which I assisted out by breaking open its 

 cocoon, and have kept in a shallow dish of water with some of the weed 

 since September 2nd, 1911, At the time of writing (October 6th), it 

 is still alive. I hoped to determine the real time of appearance of 

 the imago, but this I find very difficult to state at present. Towards 

 the end of August I captured two pale immature-looking specimens 

 which had evidently only just emerged. Throughout the period I was 

 working for the Hxmonia the larva, pupa, and imago could be taken 

 together, and on one occasion, when Commander Walker was present, 

 I brought- out of the watei- the three stages of the insect in a handful 

 of the food- plant. 



fel¥l W 



The larva (fig. 1) is a whitish grub, short and stout in appearance, 

 convex on the dorsal, flattish on the ventral surface, wrinkled along 

 the sides, and curved at each extremity. It is sparsely clothed on the 

 dorsal and lateral regions with very short, bristly, ferruginous hairs, 

 which are hardly visible except with a good lens, and look as if closely 



