Natures wonders: moth bat defenses (Introduction)

by David Turell , Saturday, September 11, 2021, 19:07 (957 days ago) @ David Turell

It's all in the wingtip shapes:

https://www.sciencedaily.com/releases/2021/09/210909124217.htm

"Researchers at the University of Bristol have discovered that the tips of some saturniid moth forewings are curiously rippled and folded. They found that these unique structures strongly reflect sound, meaning that a bat hunting using echolocation is more likely to attack the wingtip region of the moth over the body, potentially saving the moth's life.

"They also discovered that the ripples and folds of the forewing tips have evolved to act as hemispheric and corner retroreflectors respectively, meaning that they reflect sound strongly back to its point of origin. Coupled together, the folds and ripples of these wingtips cover a huge range of incident sounds angles, meaning that over the entire wingbeat cycle of a flying moth and most possible positions of an attacking bat, the wingtip would consistently produce the strongest echoes. The acoustic protection of wingtips is even stronger than that of common hindwing decoys.

"Prof Marc Holderied of Bristol's School of Biological Sciences explained: "We have demonstrated that the folded and rippled wingtips on the forewings of some silkmoths act as acoustic decoys.

"'Structurally, the wingtips act as acoustic retroreflectors, reflecting sound back to its source from numerous angles, meaning a bat would be more likely to strike the wingtip over the more vulnerable body of the moth."

"The findings, published today in Current Biology, are the latest revelation in the bat-moth acoustic arms race -- the battle between bats which hunt moths using echolocation, and the subsequent evolution of different defensive strategies amongst moths to increase their chances of survival.

"Towed acoustic decoys are a well-established defense amongst some silkmoths. These species have evolved elongated hindwings which terminate in a coiled and twisted end. The morphology of these elongated hindwings means that they generate very strong echoes, so much so that they will often divert a bat's acoustic gaze towards them, away from the exposed body of the moth, causing the bat to strike the expendable tail of the moth or miss the moth all together."

Comment: Every time teleology rears its ugly head as in this study, the wing tip adaptations must require thoughtful planning and design, and the realization, as proposed by the authors, that a flimsy wing tip is more difficult to hit in arial combat than a hardened body..