Hi Tom, this is a flatworm, belonging to the phylum Platyhelminthes. Some of them, especially some marine flatworms are very beautiful. The landliving Flatworms are restricted to moist environments; and there are also freshwater species. Here are some examples of flatworms.
http://www.pbs.org/kcet/shapeoflife/animals/platyhelminthes.html
It is clearly not an insect; insects are generally characterised by an
Exosceleton (that´s why so many of them are crunchy)
one pair of Antennae (=feelers; if something has more feelers, it belongs to the Crustacea (crabs, shrimps, lobsters and so on))
six legs (though some insects have some legs reduced)
and a segmented body with 3 parts (head, thorax (or breast) and abdomen
(that means a spider is also not an insect; body consists of 2 parts, it has 8 legs and no feelers- it belongs to the Arachnida (spiders and allies))
There are some insects however which have the word worm in their name, like the glowworms for example-
and on the other hand there are quite a lot of "worms" which are not even related, but only share the characteristics of a long, elongated body ...