Deaf moths’ sounds to escape from bats

This 2010 video says about itself:

Development of the Orchard Ermine (Yponomeuta padella) from caterpillar to moth. Filmed at the Wollenberg, Hesse, Germany.

From the University of Bristol in England:

Deaf moth evolves sound-production as a warning to outwit its predator

February 5, 2019

A genus of deaf moth has evolved to develop an extraordinary sound-producing structure in its wings to evade its primary predator the bat. The finding, made by researchers from the University of Bristol and Natural History Museum, is described in Scientific Reports today [Tuesday 5 February].

It’s already known that some species of moth have evolved a range of defensive mechanisms to evade insectivorous bats’ highly-tuned echolocation (biosonar) detection skills. The discovery of a wingbeat-powered sound producing structure in the wings of a deaf moth is completely new.

Many larger species of moth use ears tuned to detect the echolocation calls of bats to provide an early warning of approaching bats allowing them to perform evasive manoeuvres. While others, such as some silk moths, have hindwing tails that produce salient echoes which act as false targets to bats — like the towed decoys fighter planes use against radar guided missiles.

The team of researchers from Bristol’s School of Biological Sciences and the Natural History Museum, London, were studying a group of smaller British moths known as the small ermine moths (Yponomeuta species), and discovered that despite their lack of hearing they were making continual clicking sounds whenever they fly. Unlike other species of moths, that produce sound in response to detecting an approaching bat, small ermine moths have evolved to produce continual warning sounds.

The sounds these moths produce are very similar to sounds produced by larger moths, such as the tiger moths, which warn bats of the moth’s distastefulness or toxicity (known as acoustic aposematism). At night an unpalatable moth cannot provide a bat with a conspicuous warning colour, so instead it warns its predator acoustically. The team suggest that small ermine moths are acoustically mimicking unpalatable, sound producing moths, to warn bats of their own distastefulness.

Typically, anti-bat sounds are produced by structures called tymbals, small areas of thin cuticle on a moth’s body, which are connected to a muscle. As the muscle contracts, the tymbal buckles and produces a click, then as the muscle relaxes, the tymbal snaps back to its resting state and produces another click. However, the wing-based tymbals of small ermine moths are not connected to a muscle, instead sound production is initiated by the moth’s wingbeat during flight.

Liam O’Reilly, the study’s lead author and a PhD student at Bristol’s School of Biological Sciences, said: “Bat defences in larger moths are well studied, however, the defences in smaller moths are not.

“Many animals use a conspicuous visual signal such as bright colouration to warn their predators of a defence, but at night an unpalatable moth cannot provide a bat with a visual warning signal, so instead it warns its predator acoustically through a clear sound — loud high frequency (ultrasonic) clicks.

“The fact that sound production in these moths has remained undiscovered for so long reminds us of how little we know of the complex acoustic world of bats and moths.”

Following this discovery, the team are working with material scientists to find out the exact mechanism by which the small ermine moth tymbal produces sound. Specialists in buckling mechanics are working on modelling the system to artificially recreate the sounds of these moths.


How hummingbird hawkmoths fly, new research

This July 2016 video says about itself:

Hummingbird hawk-moth – Macroglossum stellatarum in slow motion

A Hummingbird hawk-moth feeding on my window-sill at 120 frames per minute.

From Lund University in Sweden:

Antennal sensors allow hawkmoths to make quick moves

December 20, 2018

All insects use vision to control their position in the air when they fly, but they also integrate information from other senses. Biologists at Lund University have now shown how hawkmoths use mechanosensors in their antennae to control fast flight manoeuvres.

When the moths need to rapidly change direction and manoeuvre, for example to escape predators, their eyes are insufficient. Instead, the receptors at the base of the moths’ antennae provide the necessary feedback. Researchers from Lund University, in collaboration with Sanjay Sane from the Tata Institute of Fundamental Research, Bangalore, have now explored the role of these antennal sensors for flight control, using the hummingbird hawkmoth (Macroglossum stellatarum) as their study model.

In their experiments, the researchers used the moths’ natural habit of hovering in front of a flower when they feed on nectar. They trained moths to visit an artificial flower to drink sucrose solution. Then they moved the flower sideways, at different speeds, while filming their responses with a high-speed camera to see how well they were able to follow the flower movements. To understand what role of the antennal sensors, they clipped the antennae, thus blocking the sensory input, and repeated the same experiment.

“Without antennae the moths were still able to fly, but they were only able to track the slow flower movements, not the fast ones. When we re-attached the antennae they worked nearly as well as before and the moths were able to track the faster lateral movements again,” explains Almut Kelber, professor at the Department of Biology at Lund University. “This is because their antennae function exactly like a gyroscope in aeroplanes. The gyroscope measures the orientation of the plane, or in this case, the moth.”

When it comes to speed, the compound eyes have no chance of matching the feedback from the moth’s “gyroscope.” The transduction of sensory information into a nerve impulse takes 1000 times longer for photoreceptors in the eye than for a mechanoreceptor. In addition, the information from the photoreceptors in the eye has to pass a larger number of neuronal connections in the moth’s brain before it reaches the muscles that control the wings. This longer chain of command adds to the delay of the visual sense compared to mechanoreception.

“Until now, researchers have believed that hummingbird hawkmoths only use visual information to navigate. This was only known from nocturnal moths before. We demonstrate that they also use antennal receptors, and showed how they work together with the visual sense,” says Almut Kelber.

Hawkmoths are not the only insects to use such a “division of labour” between vision and mechanosensation. Flies have long been known to use mechanosensory information from their vestigial hind-wings, small club-shaped structures called halters, in addition to visual information from their eyes.

“We showed that flies and hawkmoths use the same strategy to control their flight, despite very different anatomical prerequisites. They use vision for slow movements and the gyroscope for faster movements. Moths do not possess halteres, but their gyroscopes are in their antennae,” concludes Anna Stöckl, now at the University of Würzburg and one of the researchers behind the study.

Great tits eating oak processionary caterpillars

This June 2018 video is about a great tit eating oak processionary caterpillars at their nest. Paul van Heijningen in the Netherlands made this video.

This 17 June 2018 video is about great tits eating oak processionary caterpillars at their nest. Silvia Hellingman in the Netherlands made this video.

This 2 July 2018 video is about great tits eating pupae of oak processionary moths. Silvia Hellingman made this video in Drenthe province in the Netherlands.

How moths evade bats

This 5 July 2018 video says about itself:

Watch how battles with bats give moths such flashy tails

Long tails fool bats into striking in the wrong place.

Read more here and here.

From the Acoustical Society of America in the USA:

Moths survive bat predation through acoustic camouflage fur

November 6, 2018

Moths are a mainstay food source for bats, which use echolocation (biological sonar) to hunt their prey. Scientists such as Thomas Neil, from the University of Bristol in the U.K., are studying how moths have evolved passive defenses over millions of years to resist their primary predators.

While some moths have evolved ears that detect the ultrasonic calls of bats, many types of moths remain deaf. In those moths, Neil has found that the insects developed types of “stealth coating” that serve as acoustic camouflage to evade hungry bats.

Neil will describe his work during the Acoustical Society of America’s 176th Meeting, held in conjunction with the Canadian Acoustical Association’s 2018 Acoustics Week, Nov. 5-9 at the Victoria Conference Centre in Victoria, Canada.

In his presentation, Neil will focus on how fur on a moth’s thorax and wing joints provide acoustic stealth by reducing the echoes of these body parts from bat calls.

“Thoracic fur provides substantial acoustic stealth at all ecologically relevant ultrasonic frequencies,” said Neil, a researcher at Bristol University. “The thorax fur of moths acts as a lightweight porous sound absorber, facilitating acoustic camouflage and offering a significant survival advantage against bats.” Removing the fur from the moth’s thorax increased its detection risk by as much as 38 percent.

Neil used acoustic tomography to quantify echo strength in the spatial and frequency domains of two deaf moth species that are subject to bat predation and two butterfly species that are not.

In comparing the effects of removing thorax fur from insects that serve as food for bats to those that don’t, Neil’s research team found that thoracic fur determines acoustic camouflage of moths but not butterflies.

“We found that the fur on moths was both thicker and denser than that of the butterflies, and these parameters seem to be linked with the absorptive performance of their respective furs”, Neil said. “The thorax fur of the moths was able to absorb up to 85 percent of the impinging sound energy. The maximum absorption we found in butterflies was just 20 percent.”

Neil’s research could contribute to the development of biomimetic materials for ultrathin sound absorbers and other noise-control devices.

“Moth fur is thin and lightweight,” said Neil, “and acts as a broadband and multidirectional ultrasound absorber that is on par with the performance of current porous sound-absorbing foams.”

New high flying ´Icarus´ moth discovered

Male (left) and female (right) of the newly described owlet moth species Admetovis icarus. Credit: Lars G. Crabo

From ScienceDaily:

Newly discovered moth named Icarus sports a flame-shaped mark and prefers high elevations

October 9, 2018

A newly-recognized species of owlet moth recently discovered to inhabit high-elevation mountains in western North America was named after the Greek mythological character Icarus. From now on, scientists will be referring to the new insect as Admetovis icarus.

In their paper, Dr Lars Crabo, Washington State University, USA, and Dr Christian Schmidt, Agriculture and Agri-Food Canada, explain that the combination of the distinct flame-shaped mark on the moth’s forewing and its high-elevation habitat were quick to remind them of Icarus, who is said to have died after flying so close to the sun that his wings made of wax and feathers caught fire.

The study is part of the seventh volume of the “Contributions to the systematics of New World macro-moths” series, where all previous volumes have also been published as special issues in ZooKeys.

Found in the town of Nederland, Colorado, the moth was collected at an elevation of 2,896 m above sea level. The species has also been recorded all the way from central Utah and central Colorado to the Selkirk Mountains of southeastern British Columbia, including a record from northeastern Oregon. It can be spotted between June and August at night.

In fact, it turns out that the moth has been collected during surveys in the past on multiple occasions, but has been misidentified with another closely related species: Admetovis oxymorus.

While the flame mark is a characteristic feature in all three species known in the genus (Admetovis), in the newly described species it is darker. When compared, the wings of the Icarus moth are also more mottled.

Despite the biology of the larvae being currently unknown, the scientists believe they are climbing cutworms and feed on woody shrubs, similarly to the species Admetovis oxymorus.

“Finding undiscovered moths is not that unusual, even though scientists have been naming insects since the eighteenth century“, says lead author Dr Lars Crabo.

“The Contributions series, edited by Don Lafontaine and Chris Schmidt, in which this discovery is published, really encourages professional and citizen scientists alike to go through the steps necessary to properly name the species that they have discovered. This series of seven volumes also includes a new check list for the United States and Canada, which has led to a re-kindling of interest in moths during the last decade.”