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Dancing woolly aphids will probably stab you

The views expressed are those of the author and are not necessarily those of Scientific American.


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“Hey you guys are having a party? Where’s my invite? JK, JK it’s cool, I don’t have a letter box anyway. Where should I stash my beers? Why isn’t there any music playing? Oh is this one of those silent discos…”

“Sir, this is a very serious operation, we’re trying to save lives here and we need you to stop dancing like that immediately.”

“Nope, too late. Look at this hip movement. Look at it. You don’t want to mess with this. Did someone say limbo?”

“No one said lim–”

“You know, we should really rethink our defensive strategy because if I see one more Hawaiian shirt while we’re in the middle of a crisis–”

“Conga line!”

****

Commonly known as woolly aphids, these fuzzy little guys are distinguished by the long, white, waxy filaments that cover their posteriors. Not to be confused with the woolly aphids from the Eriosomatinae family, which terrorise apple trees under an expansive blanket of white fluff, these are beech blight aphids (Grylloprociphilus imbricator), a species that lives off the sap of beech trees in North America.

A population of beech blight aphids will settle onto a beech tree, amassing by the thousands across its branches like freshly fallen snow. Here they’ll pierce the bark with their syringe-like mouthparts called stylets and suck the sap out. Their calling card is a dark, ugly build-up around the tree caused by sooty mold fungi (Ascomycete), which turn aphid excretions called honeydew black while extracting the nutrients. Despite the worrying appearance of this thick, black tar, these aphids are not considered a serious threat to their beech tree hosts – at the very worst they might distort or slightly stunt the growth of the leaves or kill off a small branch.


(This video confuses beech blight aphids with woolly beech leaf aphids (Phyllaphis fagi), but it’s too great not to use. Unlike G. imbricator, which are found primarily on branches and twigs, P. fagi stick mainly to the undersides of leaves.)

Known affectionately as the ‘boogie-woogie aphid’, when a colony of beech blight aphids is disturbed, they’ll lift their fuzzy posteriors high in the air and pulse them in unison as a warning to predators. Sort of like the black lace-weaver spiders, which when young, will gather together in a group of 160 siblings and contract their bodies to make their web throb in response to a predator. Watch a video here.

A 2001 study led by biologist Shigeyuki Aoki from Rissho University in Japan discovered that, like the black lace-weaver spiderlings, it’s the beech blight aphid nymphs, not the adults, that respond to predators. When the researchers introduced a number of predatory moth larvae to colonies of G. imbricator, aphid nymphs of all stages (or instars) of development would raise their posteriors and walk around, waggling their abdomens back and forth. Those in the middle of feeding would simply waggle themselves on the spot.

And this was no false warning. These nymphs were young, but they were also aggressive. “A total of 69 nymphs attacked the ten tortricid larvae, and 47 of them did not detach themselves from the larvae even after being deposited in ethanol. We ascertained under a dissecting microscope that many of them, including nymphs of all four instars, stung the larvae with their stylets. We confirmed the stinging behaviour by placing some aphids on our hands,” the team wrote in their The Florida Entomologist paper. “In this species, nymphs of all four instars played a defensive role, but 4-instar nymphs [a more developed stage] were the main defenders.”

So less sweet fairy jig and more menacing war-dance performed by children.

You can read more about the black lace-weaver spiderlings – also encouraged by their very own mum to eat her alive before venturing out of the nest – in my new book, Zombie Tits, Astronaut Fish and Other Weird Animals. Pre-orders get a discount, so click here to pre-order your copy.

Bec Crew About the Author: Bec Crew is a Sydney-based science writer and award-winning blogger. She is the author of 'Zombie Tits, Astronaut Fish and Other Weird Animals' (NewSouth Press). Follow on Twitter @BecCrew.

The views expressed are those of the author and are not necessarily those of Scientific American.





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