My guess would be Flower Thrips. They aren't worms but are elongated in shape, yellowish-tan in color, and tiny. They feed on plants and prefer the flowers specifically. Petunias and Verbenas seem to be favorites. They can behave as you've described because they are attracted to certain colors like white, blue, and especially yellow. What I've read is that when they bite humans they are just taste-testing to see if you are a tasty flower or to get moisture from the perspiration on your skin. It does sting but doesn't seem to have residual effects in most people. This year there must have been a population explosion due to the warm winter. I've really never noticed them too much in years past but a plague of them descended this year. Thankfully, a combination of heavy rain storms and Minute Pirate Bug predation has greatly reduced the number of thrips here at the moment. (thrips is plural and singular) If you know what plants they are breeding on, Spinosad is supposed to be really good at killing thrips while having less toxicity to other good insects if used properly. You'd need to spray late in the evening when bees have stopped foraging. I have no experience with this however. I was going to try the Spinosad but nature took care of most of them for now. However, I'm keeping an eye out for them by looking at flowers for damage or the actual thrips. Pinching the base of the flowers and/or blowing on the flowers can cause the thrips to start moving around.