2 7 8 THE BRITISH NATURALIST. [December 



of the river Ribble, and being carried out to sea, was able to outlive its 

 full briny bath, and return with the incoming tide. I am confirmed 

 in this idea by the Rev. A. E. Eaton, M.A., who tells me that species of 

 Trichoptera have been found in tidal pools, on the coast of New 

 Zealand, and that he himself found plenty of small Hydroptilidae, to 

 which family no doubt both species (Figs. 3 and 4) belong, in some 

 salt or brackish streams in Southern Algeria, on the borders of 

 the Sahara Desert. Mr. Eaton also ■ drew my attention to Mr. 

 Kenneth J. Morton's interesting account of the metamorphoses 

 of Oxyethiva costalis in the Entomological Monthly Magazine for 

 February, 1887. The latter gentleman kindly sent me a photograph 

 of one of his specimens, and ultimately I sent him both the marine and 

 Loch Tay mounts for his examination. In reply, he expressed the 

 opinion that both specimens (Figs. 3 and 4) belong to Oxyethiva ; but 

 that the transparent case of my marine specimen differs from 0. costalis in 

 the anterior opening not having so distinct an everted rim, and, 

 further, that the posterior margin is rounded, whereas in 0. costalis 

 this margin is always more or less truncate ; but these cases, he says, 

 can probably be made and altered or enlarged with considerable 

 rapidity. 



I have, therefore, in Plate XII. given, in more highly magnified 

 detail, the difference in structure between the two larvae, especially of 

 the head and claw, Figs. 5 to 8. You will see there is a specific 

 difference in the upper claw. In Fig. 6 this works separately. Then, 

 both the head and legs of the Loch Tay specimen Figs. 4 and 8, are 

 much more covered with hair than my marine specimen, Figs. 3 and 7. 



Mr. Morton thinks the presence of my specimen in the open sea was 

 an accident ; for he says : " Many Trichoptera are found in tidal rivers 

 near enough the sea to be slightly brackish, and I have seen cases 

 taken from a streamlet at a place which at high water was covered 

 by the tide. It might be worth while to keep a look out on the 

 wood or ironwork of the pier early in June for the perfect insect, which, 

 though rather minute, is an intensely active and very hairy fly." 



I must get my friends of the Preston Scientific Society to hunt 

 along the streamlets running into the Ribble Estuary for some of these 

 caddis larvae or their cases, and try to rear them as Mr. Morton 

 has done with Oxyethha costalis. 



The Hydroptilidae are all very small, and some of them fix and 

 weave round their cases a secretion of fine silk threads. Diatoms are 

 often found adhering both to the webs and the capsules. The wedge- 

 shaped character of the case in O. costalis is very distinct ; mine is 

 more vase-shaped. The heads in both larvae are much alike, with 

 dark chitinous cephalothorax and distinctly marked segments, provided 

 with the usual three pairs of legs, the first of which possess strong 



