CADDIS-FLIES. 83 



it is sometimes found crawling about without any 

 protection. 



The length of the larva when full grown is about J inch. The head is 

 round, much flattened above, dark brown and horny with the surface very 

 rough. The prothorax is small, cylindrical, and horny throughout. The 

 meso- and meta-thorax are slightly larger, and furnished with dark-brown 

 horny plates on the dorsal surface. The segments of the abdomen are 

 stout, rather soft, and dull greenish-brown in colour. There are two 

 rather elongate appendages at the posterior extremity of the larva, each 

 furnished with a very strong hook, and a conspicuous tuft of long brown 

 bristles. The under-side of the mesothorax is furnished with two branching 

 white filaments. The metathorax and the first seven segments of the 

 abdomen are each furnished, on the under surface, with four branching 

 white filaments. The last segment but one has two filaments, and the 

 terminal segment two brushes of brown bristles, in addition to the above 

 described terminal appendages. The anterior pair of legs are very short 

 and stout ; the two other pairs also short and rather slender. 



This larva is a favourite article of food with the trout 

 (see tables pages 93-98), and as it occurs in large numbers 

 during the winter, and is full grown in very early 

 spring, it must be an important item in the dietary 

 of that fish. 



When full grown this larva constructs a cocoon of 

 rather large stones, loosely joined together with silk r 

 but firmly attached to a boulder in the bed of the stream. 

 The pupa is simply enclosed in this cocoon, and is not 

 encased in any inner horny case. The perfect insect 

 appears in December and January, and is often ex- 

 tremely abundant after dark, when large numbers may 

 be observed either flying over the stream or running 

 with great agility over the stones and herbage near 

 the banks. 



Genus POLYCENTKOPUS, Curtis (1835). 



"Antennse strong, the joints short, the first bulbose. Maxillary palpi 

 with the first and second joints very short, stout, almost transverse ; the 

 third and fourth cylindrical ; the fifth as long as the others united, stout at 

 the base. Anterior wings elongate-oval, densely pubescent, with short 

 fringes. Posterior wings shorter, much broader, with obtuse apices ; apical 

 fringes short, those on the anal border longer ; anal lobe well developed ; 

 discoidal cell open, and the two first costulae generally connected near their 

 middle by a small nervule. 



" Distribution. — Europe, America, Ceylon" (Hutton). 



POLYCENTROPUS PUERILIS. 



Polycentropus puerilis, McLachlan, Journ. Linn. Soc, 

 vol. 10, p. 204, pi. 2, fig. 8 (1870). 



(Plate XL, fig. 9, 10 larva enlarged.) 



This pretty and easily recognised caddis-fly has been 



