Owlet moths can sense echolocation of the bats that are hunting them

Spring is the flowering season: wildflowers, fruit trees, bulbs, ornamental shrubs, vines and other plants bloom in profusion from March through June. The abundance of blossoms attract lots of nectar-feeding insects, including a large family called the Noctuids, or owlet moths.

The Noctuids, which means “little owl” in Latin, from the adverb noctu meaning “night” or “in the night-time,” are one of the largest families of moths — there are about 12,000 species of owlet moths worldwide.

Most owlet moths tend to have stocky bodies and slender antennae that are described as filiform, meaning “thread-like,” instead of the feathery antennae that many moths possess. Many owlet moths are also somewhat furry on their bodies.

Last week I was watching what appeared to be some Autographa moths, which is a genus of owlet moths, as they were nectar-feeding on flowering crab apples and lilacs. Most moths are nocturnal, but some are active during the day as well.

The Autographa moths that I was watching were active in the afternoon, along with other pollinators like bumblebees, honeybees and hoverflies. As the afternoon began to shift to evening and the light began to fade, however, all the bees disappeared but even more moths began to flutter from blossom to blossom.

The owlet moths had to be wary of one of their chief predators: bats. While bats consume many different kinds of flying insects, plump-bodied moths are one of a bat’s favorite prey creatures, since they contain lots more nutrition than most insects, like a spindly mosquito, for example.

To help them detect the presence of bats, owlet moths have on their thorax what is called a tympanal organ, which is a thin membrane stretched tight across a frame with an air pocket behind it, as well as some sensory neurons. The name is derived from the timpani, or kettledrum, which functions in a similar way.

Owlet moths use their tympanal organs to detect the echolocation calls that bats use to find their prey. The moths are usually most sensitive to the frequencies of bats species in their area.

When moths detect the echolocation calls of hunting bats, they will halt mating behavior, such as wing flapping. If an owlet moth is in flight and it senses a nearby bat’s radar-like echolocation call, the moth will start flying erratically, suddenly diving or cartwheeling and taking evasive measures to escape from the hunting bat.

In addition to this specialized hearing ability, owlets and other moths tend to have an excellent sense of smell, since they often fly at night when vision is reduced, and their olfactory organs help them find flowers by scent.

Owlet moths begin life as caterpillars that hatch from eggs typically laid in the soil. The larvae of some owlet species are called cutworms, armyworms or loopers, and in large numbers can do damage to farm crops, especially seedlings. Most owlet caterpillars are green or brown in coloration.

When the caterpillars reach full growth, they form a pupae, inside of which they undergo the metamorphosis transformation. After pupating in the soil, adult moths emerge and begin their flights in search of nectar or honeydew.

Owlet moths tend to be plumper and more noticeable than many moths, and they are flying now, while keeping alert to the danger of bats hunting on the wing. Owlet moths are another interesting part of the tapestry of life in the Tehachapi Mountains.

Have a good week.