Whether they can or can't crawl back up, new crops of them hatch out all the time. Like aphids, Japanese, Fuller, Curculio and other beetles as well as all other insects which suck or chew the plants, you have to continually battle them during their "season" using whatever methods you've selected. I'm not recommending any method nor attempting to encourage you to go "nuclear" on them, but the less toxic your method, the more interactive you have to be with the control. With more generations regularly hatching from eggs, and more eggs being deposited as long as conditions favor their reproduction, new "slugs" are appearing daily or every few days. So, if you're knocking them off, picking them off or washing them off, you have to be diligent at it. Pick, knock or wash them off daily or every few days as your time, energy and infestation dictate. Or, go with an organic control like the bacterial Spinosad, which knocks down all of the hatched slugs at once for two weeks. That has to be sprayed twice monthly unless it's all washed off by a heavy rain. Yes, it can kill the predators, too, but all "insecticides" will. The point is, you have to determine whether you want to constantly battle them or take stronger measures against them. They not only cause unsightly damage, but ANYTHING which reduces the green leaf area of the rose, inhibits, reduces its ability to feed itself. Reduce the leaf surface area sufficiently and you inhibit the plant's immune system, weaken the plant,by causing it be malnourished, making it more susceptible to other damaging factors such as fungal attacks and potential freeze damage in winter, if that is a possibility where you live. Kim

I have posted some photos. Sorry they're not clearer. My camera couldn't focus on the caterpillars. Here is a link that might be useful: Photos of caterpillars -sorry about the quality

Ok, how about this? "Euonymous, peonies and lilac are among the plants frequently damaged by adult root weevils." There is a small picture of the kind of damage they do. You can find more on the web. They eat notches out of the leaves. Here is a link that might be useful: Colorado State Uni Root Weevil page

Root weevils. Look for them at 10 pm or later.