Which is out of place: butterfly, ant, toad, or bedbug? - briefly
The toad is the sole amphibian among the list; butterfly, ant, and bedbug are all insects.
Which is out of place: butterfly, ant, toad, or bedbug? - in detail
Among the four organisms— a lepidopteran, a hymenopteran, an amphibian, and a hemipteran— the amphibian differs fundamentally.
The butterfly belongs to the class Insecta, order Lepidoptera; it undergoes complete metamorphosis, possesses scaled wings, and feeds primarily on nectar as an adult.
The ant also resides in Insecta, order Hymenoptera; it exhibits a caste system, lacks wings in most castes, and consumes a variety of organic material.
The bedbug is an insect, order Hemiptera; it is a hematophagous ectoparasite with piercing‑sucking mouthparts.
The toad is a member of the class Amphibia, order Anura; it possesses moist skin, undergoes metamorphosis from a larval tadpole, and lives both in water and on land.
Key distinctions placing the amphibian outside the group:
- Taxonomic class: three are insects; one is an amphibian.
- Physiological traits: amphibians have permeable skin and lack an exoskeleton, unlike the chitinous exoskeleton of insects.
- Ecological niche: the toad occupies both aquatic and terrestrial habitats, whereas the insects are primarily terrestrial.
Therefore, the toad is the outlier in this set.