A green, segmented worm was found by one of our readers this summer, and she wonders what it is. According to our reader, this critter was similar to a tomato worm in its color, texture and possession of a “pincher mouth”, but was much larger, and had “little blue and yellow” knobs patterned along its body with black prickles sprouting from them.
Despite our reader not providing a picture of the worm she found, her meticulous description was enough for us to identify this worm as an emperor moth caterpillar. Emperor moths are common in the UK, and are widely regarded as beautiful, both in their matured form, as well as their larval form, the caterpillar. Our reader mentioned that the size of the caterpillar she found was almost an inch in diameter, and about 3-inches long. These approximations are not actually far off from their average length, which is 2 ¼-inches. The yellow knobs our reader described are, in fact, breathing tubes called spiracles.
An emperor moth caterpillar’s diet consists mostly of heather, alder blackthorn, hawthorn, and other plants. In relation to their wide variety of dietary options, emperor moths can also sustain in various habitats, including, but not limited to: bogs, hedgerows, and sand dunes. Emperor moth caterpillars are not pests by nature, and the risk of an infestation is low. However, it is not impossible that an emperor moth wanders into one’s home and lays eggs, thus creating an infestation. We were not informed where our reader found this worm, whether inside or outside, but regardless, we encourage our reader to ensure that her window screens are of good quality, and that all cracks in her walls or flooring are sealed. This will be helpful in ensuring any insect or creature does not saunter into her home.
Furthermore, according to ‘Ireland’s Wildlife’ although the emperor moth is often mistaken for a butterfly, it is most definitely a moth. The way one can know this for sure is by studying its mating habits and behaviors, which differs between butterflies and moths generally. Whilst butterflies rely on their sight to search for potential mating partners, moths use their sense of smell to court their mates. From up to one kilometer away can male moths detect the special pheromone that females use to attract their potential mates. These capabilities are quite amazing for a creature so small.
To conclude, the green, segmented worm our reader found was an emperor moth caterpillar. This creature is beautiful in all its stages, and should not be feared.