The Caddis-Worm and its Houses. 315 



they have even the reputation of eating the ova of trout. 

 But after taking into consideration the leathery case and 

 the roundness and smoothness of the ova, and the difficulties 

 which they must present to the caddises, I am inclined to 

 doubt the assertion that they cause in any way their injury. 

 I have placed the ova of trout in the same vessel with caddises, 

 but never knew one to be eaten, and even have known a caddis 

 to incorporate ova into its case. But with the other-named 

 creatures I myself have been an eye-witness of their rapacity. 

 Indeed, as far as the mollusks are concerned, caddis-worms 

 seem to consider them an extremely delicate food, judging 

 from the amount of them they consume when they can get the 

 opportunity to do so. I will here give a little anecdote to 

 prove this, and also to show in what manner I discovered their 

 rapacity in that way. 



I had some fresh-water mussels, belonging to the family 

 Mijtilaceoe, and called the Breissena polymorpha. They were 

 given to me rather as curiosities, and which I kept in an 

 aquarium, containing, amongst other things, caddis-worms. 

 After a short time I found to my mortification a great number 

 of my mussels were dead, as I at first thought, although I 

 was surprised that I never found any trace of the dead crea- 

 tures, their shells being always open and clean. This state of 

 things went on for a few days, my shells, or rather their in- 

 habitants, vanishing in a most mysterious and unaccountable 

 manner ■ until one day I saw a caddis walk deliberately up to 

 one of the mussels, whose respiratory orifices were protruded 

 from the partly open shell of the mussel, which was enjoying 

 itself in the nice bright water of my aquarium, not dreaming 

 that there was any danger so near to it. 



Well, as soon as the caddis had reached close to the mussel, 

 it seized hold of the siphoned orifices, which are the respiratory 

 orifices of the mussel, and then devoured the poor creature up. 

 Beginning with the part that it first attacked, and continuing 

 its havoc until the shell, or rather the two shells (for mussels 

 are possessed of two shells), were completely emptied. Other 

 caddises were also discovered demolishing others of the same 

 kind of mussel, after a similar manner as that just described. 



The mussels which are mentioned here are natives of 

 northern and eastern parts of Europe. They were first dis- 

 covered in England in 1824, in the Commercial Docks, and 

 have been supposed to have been brought to England amongst 

 some timber. They have been carried to the River Lea, and in- 

 creased plentifully in the reservoirs and even in the water- 

 pipes of the New River Company in the Green Lanes. By 

 their fertility they have become almost a nuisance, and I may 

 confidently suggest to the New River Company the importation 



