Today I noticed that my English Elms were being eaten by hungry caterpillars.
I have four trees - all had been rather severely eaten. On three I was able to locate and destroy 3 rather large green hungry caterpillars. they are good at hiding!
My question - does a caterpillar eating most of the leaves off a limb damage the plant ...more than aesthetically? I am wondering/hoping - probably ignorantly/stupidly - that perhaps these leaves being eaten is acting like a random defoliation and it might encourage more buds? Some branches were basically defoliated by the caterpillar. It has happened reasonably quickly, I reckon within a week or two. I pride myself on keeping a close eye at my plants but clearly I let myself own here!
So permanent damage, yes or no? Is there an upside... will this stimulate new growth?
Apologies in advance if these questions are patently ridiculous.

PS - Question: When has a hobby really got its claws in?
Answer: When you decide you need a magnifying glass. True ... my reading glasses are not enough - I want and need to look more closely at my plants. Does anyone else use magnifying glasses and if so, any ideas on good ones to buy?