Frank Stevens, Adventures in Pondland, Londres, Hutchinson & Co., 1905, p. 243-246.
« Now, » remarked Lemna, « I will show you the cousin of the May-fly. That is the Caddis-fly. They seldom visit the ponds, as they prefer a running stream. Still, there is one here who will, I think, amuse you ; » and she pointed to a cluster of Planorbis snails, who seemed very busy.
« That’s not a caddis, » said Jackie. « It’s only a lot of catherine-wheel shells. »
« Watch it closely, » replied Lemna, with a smile.
One of the snails now pushed his black head out of his shell, and lazily thrust out his eyes to survey the situation.
« There ! » said Vi. « That is only a snail. I beleive Jackie is right. »
Meanwhile the snail seeing that it was a fine afternoon, thought this an excellent opportunity for a walk, to see what sort of weeds he could get for tea. He started, therefore, bravely, and began to pull himself along. At first he seemed to move slightly ; then, finding some difficulty, he tugged and strained very hard, but without effect. This evidently puzzled him, so he drew in his horns and retired into his shell to think the matter over.
« Why can’t he move ? » asked Vi.
Lemna laughed heartily.
« Because he has been taken prisoner, » she replied.
« Come to the other side. »
She led them round the clump, and there, in a little grotto of shells, they saw the caddis-worm.` »I can see the caddis, » said Jackie ; « but I don’t understand why the catherine-wheel shell was not able to walk away. »
‘Then I will tell you, » said Lemna. « Mr Caddis is very like Miss May-fly- a nice, soft, tender, juicy morsel for all the greedy people live here. He has to hide, somehow, and the way he does it is to build himself a house. He collects all sorts of things, and carefully glues them together. Then he gets inside, where he hooks himself quite tightly, so that he can’t be pulled out by any of the other beasts who want to eat him. But he made rather a mistake this time, and built a live snail into his house. »
« How very awkward ! » said Vi.
« For the snail-yes, » replied Lemna. « Now you see hat happened. Mr Snail wanted to walk away while Mr Caddis was having a nap, and he began to pull one way. When Mr. Caddis felt the strain, he held on the weeds with his forelegs. »
« And they had a tug-of-war ! » exclamed Jackie.
« Yes ; and Mr. Caddis won, » said Vi.
« He always does, » replied Lemna. « He is very fond of his home, and takes care that nothng robs him of it. »
The worm, thus rudely disturbed in his nap, and thoroughly awakened by the activity of his house, now began to rawl forward, dragging his grotto behind him.
« Look, Vi ! » said Jackie. « He’s walking along. Isn’t he funny ! »
« What a heavy thing to pull all over the place ! » said Vi.
« It would be if he were on dry land, » said Lemna.
« But it’s just as heavy down here, isn’t it ? » asked Jackie.
« Yes ; but not so difficult to move, » replied Lemna.
« Things under water appear to lose their weight, and are moved much more easily. »
Jackie had the glimmer of an idea, which he wanted to express.
« It’s like the dive rat the seaside, « he said thoughtfully. « don’t you remember, Vi ? He had great, heavy leaden soles on his boots, and weights on his chest, and couldn’t move about a bit until he got under water when he walked quite easily. »
‘That’s right, Jackie, » said Lemna. « The caddis-worm is the diver, and his shell cottage is the boots and heavy weights. »
« But isn’t it very rough and nastry inside ? » asked Vi. « I should think the snails’shells would hurt him if he has a soft body. »
« So they would, » replied Lemna, » but that he is careful to line the whole of his house with soft silk, which is the same sticky stuff that he uses in glueing the shells together. »
« How clever of him ! »said Vi. « But what if he can’t get snails for his house ? »
« He doesn’t always build with snails, » replied Lemna. « Sometimes he uses grains of sand-then he is most particular to secure grains all of one size ; sometimes he uses sticks and straws, and I have herad that naturalist often give then glass beads, out of which they build very pretty houses. »
« How jolly ! » said Jackie. « I suppose he’s very proud of a house like that. But what is he doing now ? He seems to be spinning, like my silkworms. »
The caddis was evidently very busy, covering the door of his house with delicate strands of silken fibre.