Because if it had been pulled hard enough to come out, it might have been torn to pieces, it is such a tender little thing, and it holds fast so tightly.
So the best way to remove it safely is to break its case bit by bit from around it.
It does no harm to break its case if one is careful. It will soon build another.
Yes, this larva has no distinct thorax. It is like the larvæ of the dobson, the aphis lion, and the ant lion in that respect.
See! John has found one whose tube is made of quite large stones as compared with this tube of fine sand that we have broken open.
Some caddice larvæ build houses of wood instead of stone. They stick little twigs together, and some use little pieces of leaves.
Others again use tiny snail shells which, as you can imagine, make very pretty cases.
Our little caddice has made a neat little house of fine sand grains very nicely put together.