Find the odd number / letters / word from the given alternative.

The odd one out is the butterfly. The other four insects are all considered pests, while butterflies are not.

Houseflies, mosquitoes, and cockroaches are all common household pests that can spread disease. Spiders are not typically considered pests, but they can be a nuisance if they build webs in unwanted places. Butterflies, on the other hand, are beneficial insects that help to pollinate plants.