Earwigs. At the first sign of problem, this pest is number one on the list.

Try this; put a short lenght of hose...about 12 to 18 inches in the vicinity of the plants. Early in the a.m. go out with a bucket of soapy water, lift the hose and tap it over the soap. See what falls out.

Earwigs is the one big reason why I never try to take dahlia inside, they are a beggar since they hide in amongs the petals.

The earwigs like it moist and munch at night, but hide during daylight hours. Trying to see them during the day is pretty well impossible.

Another method if you dont have a handy hose to destroy....roll up a newspaper section....place it in the vicinity and dampen it. In the morning, go out and collect your newspaper.

Sometimes too, just like catching slugs and snails, lay a board....about 6" wide...12" long near the plants. In the early morning, peek under it. They're fast movers so be prepared.