Something is eating our butter lettuce
Thanks for your butter lettuce question and photo. A number of pests enjoy lettuces including aphids, cutworms, cukes beetle, earwigs, loopers and slugs among some others. You did not mention any bug residue evidence such as from aphids or slugs. Among the other pests listed, earwigs are less noticeable as they are night feeders. Earwigs will migrate to a rolled, damp newspaper left overnight near your lettuce. If earwigs are the present , they will migrate to the newspaper, so dispose in trash bin. Also as earwigs are crawling insects and prefer a damp compost-like environment, kept area debris free and create a dry gravel barrier around the lettuce. Hot pepper spray or garlic repellant are also useful deterants.