Why don't you inspect your plants in the early evening and then later towards 9PM. If you have slugs or snails they will also munch on the leaves so you should have chewed up leaves.

Here's a second pic: Here is a link that might be useful:

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.

sasha-nh, if the dahlias are otherwise healthy I wouldn't worry about this bug. If you really need an id, here are 3 suggestions. It may be that you're trying to get too close, lenses have different limits. Try backing up a bit for a better chance the camera will be able to focus. Then, try putting the bug on a larger surface - like a table - and compose the photo so there are no distant objects in the frame. The camera is apparently trying to focus on the background (the car at the curb, the wrought iron stairway banister, the gravel, all of which are crystal clear!). You may have it in 'landscape mode' (if it's that kind of camera) or you're not giving it time to detect and focus on the bug; maybe if there's nothing BUT the bug in the field of view it will work better.