HYDROCAMPA ST A GNAT A. 109 



fourth, and fifth segments, sometimes most marked 

 on the fourth and fifth; the spiracles are of the 

 ground colour, ringed with brown ; some extremely 

 minute hairs, one in each usual tubercular situation, 

 can only be seen with the aid of a powerful lens. 



When the larva has fed up on the soft, narrow, 

 ribbon-like, floating leaves of S. simplex, it cuts off a 

 couple of pieces of the plant, varying in length from 

 about three-quarters to nearly an inch, without regard 

 to their being equal in size ; these it spins securely 

 together and moors with silk near the edge to a 

 floating leaf; thepuparium thus made lies horizontally, 

 partly or entirely submerged. 



But when S. ramosum is the food-plant, the larva 

 chooses a situation close to the outside edge of a leaf 

 in an almost perpendicular position, and there, low in 

 the water, attaches a piece of the plant, broader at the 

 lower than at the upper end, and draws it round 

 itself close to the leaf, on which it looks like a natural 

 excrescence, being about an inch and a quarter in 

 length, rather bluntly rounded off below, and for half 

 an inch tapering to a point above. 



The cocoon is of white silk, apparently quite dry 

 within, and closely enveloping the pupa with the old 

 larval skin sticking behind ; the pupa itself is a trifle 

 over three-eighths of an inch in length, of moderate 

 slenderness, the head well produced, the back of the 

 thorax gently rising from it, and from thence the 

 width is uniform to the ends of the wing-covers ; these, 

 though well defined, are pressed close to the body ; 

 the abdomen begins to taper from the tenth segment, 

 to which the ends of the leg- pieces reach, projecting 

 free ; the tip of the abdomen terminates in a hook, 

 curved downwards ; the colour is a deep bright yellow, 

 a little inclining to orange-yellow; a narrow brown 

 streak obliquely crosses each eye-piece ; three spiracles 

 on either side are conspicuously prominent on circular 

 swellings, paler than other parts, and are like nipples 

 of brownish-red with rather darker orifices ; the other 



