45 



curious sculpturings seen on limestone pebbles, on the shores of 

 Swiss lakes, may in part owe their production to the action of these 

 larvge. The RhyacopMlkhv, are so far exceptional, that in them 

 the pupa is enclosed in a special cocoon lying free inside the case, 

 whereas in all others there is no such cocoon. 



A few words as to the form and structure of Caddis-worms. 

 You will observe from the examples I exhibit, preserved in alcohol, 

 that there is a certain vague resemblance to the caterpillar of a 

 moth. But all Lepidopterous larvae possess in addition to the six 

 true thoracic legs (which are very strongly developed in Caddis- 

 worms), a varying number of prominences along either side of 

 the ventral surface, termed pro-legs ; these are never present in 

 Caddis-worms. But the latter have two strong hooks at the 

 tail-end, by means of which they resist attempts to drag 

 them from their case, certain humps at the base of the abdomen 

 also assisting in this ; the consistence of the body is soft, excepting 

 the head and thoracic segments, which are horny in texture, and 

 which alone are extended from the case when the larvae are 

 travelling or feeding. Eespiration is mostly effected by means of 

 variously arranged filaments on either side of the body, forming 

 a kind of external gills or branchiae, which absorb air from the 

 water and convey it to the internal tracheal tubes. 



Those Caddis-worms that live in standing waters are not 

 difficult to rear in an ordinary aquarium, and they may be forced 

 to form cases of all kinds of odd materials by depriving them of 

 their original dwellings; but to my mind, this result is not 

 equivalent to the trouble it occasions. Those that live only in 

 swiftly-running, strongly-aerated waters, are far more difficult to 

 rear in confinement, unless a special apparatus be provided for the 

 purpose. 



The greater part of this paper has been devoted to consideration 

 of " Caddis-worms,"' or of the cases formed by them. Now, as to 

 " Caddis-fiies," or the insects produced from these " worms." To 

 many of you these are far less familiar. If you examine the con- 

 tents of the drawers before you, it will be seen that although not 

 possessing any great amount of striking colours, the forms are 

 very varied. You will also, I think, notice a vague resemblance 

 to moths pervading the whole, but I would remark that true 

 "scales," the colours and arrangement of which produce those 

 beautiful designs on the wings of moths, are not present in Caddis- 



