Difference in hooks

Wanting to increase my knowledge of flys I’m wondering what is the difference between a scud hook, a pupa hook, and a caddis hook ?

You can tie a scud or pupa with the same style hook but, the caddis need a lighter hook because the fly floats.

Bob

What Bob said and:

Emerging caddis ARE pupa. Caddis adults are tied on straight shank dry fly hooks,

From my understanding its a pharate adult… Fishing for this stage of the insect is useless as they
emerge from the water very fast unlike the mayfly,

I do agree with silvers hook type and use for the adult. w/Pupa a heavier type may suit better.

2cents - sm