1875.1 103 



weed ; often they would ascend ii little way on the side of the glass 

 vessel and fix themselves there with only their liead downwards and 

 projecting into the water, while the other end of their casea above it 

 on the glass would have a bright silvery air bubble. 



Sometimes they would descend beneath the surface of the water, 

 down the side of the glass, for an inch or two, and even more ; and then, 

 while crawling, they often protruded as many as eight segments, 

 showing a line of silvery sparkles along each side in the spiracular 

 region, the other parts of the body appearing blackish. 



On the 16th of the month, having noticed that one had remained 

 at the very bottom of the water, hidden entirely in its case, for some 

 time, I removed it to another vessel of water, the better to observe its 

 behaviour : at first it floated on the surface, but after a few minutes 

 came out of the case as far as the fifth segment, and, by crawling, soon 

 managed to arrive at the side of the glass, along which it continued to 

 crawl at the level margin of the water, occasionally turning itself round 

 within its case, and coming partly out at the other end, thus proving 

 the case to be open at both ends, a fact which was not suggested by 

 its appearance. The external figure of the case was of an irregular 

 oval form, nearly half-an-inch in length, and varying in width from 

 two to three lines, the leaves of which it was formed overlapping each 

 other, but in an irregular manner, and so contrived that a leaf or two 

 should hang down and mask the openings at the ends, when the 

 occupant, as was often the case, remained quiet within : the two ends 

 of the case are not quite alike in their fashioning, and the whole thing, 

 when the larva is not seen, very much resembles an accidental accu- 

 mulation of some of the duckweed, so slight is the eminence which it 

 causes above the general level of the surface. 



When the larva reposed just so far within its case as only to show 

 a little of its head, there was the smallest conceivaljle silvery sparkle 

 lurking at the bases of its antennal j)apilUc, and also about the mouth ; 

 but when it was in motion with two-thirds of its body beyond its case, 

 this quicksilver-like aj)pea ranee of air in water was exhibited more 

 extensively along each of its sides as a broad baud, and even the bases 

 of its anterior legs were encircled with radiance, and sparkling with 

 each movement ; this luminous appearance changed its position with 

 tliat of the larva, according to the .angle of light in which it was 

 viewed ; sometimes, behind the second segment, the back appeared 

 completely silvered over, and sometimes the belly ; and, at other times, 

 transverse silverv lines marked the segmental divisions. 



