ON SALT WATER INSECTS. 



43 



rude case or tube, almost wholly submerged, formed of 

 the debris collected upon the surface of the leaves. 

 The larva was exceedingly active, moving briskly about ; 

 or, if in its case, rapidly drawing its body in and 

 out, and snapping with its long curved mandibles at 

 the vegetable refuse within reach. b 



It also fed upon the fine sea-weeds, 

 such as the green filamentous spe- 

 cies, and a species of Ceramium ; 

 and occasionally eat into the side of 

 a Terebella-like worm, also found 

 living on the surface of the leaves. 

 Its food, then, mainly seems to con- 

 sist of sea-weeds, the red kinds rig. i. 

 coloring the intestine and faeces brown, but it also prob- 

 ably consists in part of animal matter. 



The body (Fig. 1, a, enlarged about three times) is cyl- 

 indrical, slightly diminishing in size towards the end. The 

 head is slightly flattened, and quite free 

 from the thorax. The pair of prothoracic 

 legs are very extensile, but retracted almost 

 within the body when the head is bent upon 

 . X the breast. The three thoracic rings are a 

 Fig. 2. little larger than the adjoining abdominal 

 ones, and the sutures of all the segments are but faintly 

 marked. The pair of anal legs are long and well devel- 

 oped, and terminate in a single crown of a 

 hooks (Fig. 2 ; a, portion of the dorsal 

 vessel), which can be entirely retracted 

 out of sight. In the forelegs the hooks 

 are much more numerous (Fig. 3, a), and 

 arranged in longitudinal rows, about 

 twenty-five in number, those on the upper 

 side of the tip being much the largest ; 

 those at the base being minute. The tra- 

 cheae were distinct, the two main branches 

 extending along the whole body, from the 

 last abdominal to the prothoracic segment. 



It is pale whitish in color, the thoracic rings being 

 tinged on the harder parts with green. It is .22 to .25 

 of an inch in length. 



Fig. 3. 



