BBC Focus - 03.2020

PAUL BERTNER/MINDEN/NATUREPL.COM,

FLPA

DUSTAWAY/FLICKR, EMANUELE BIGGI/NATUREPL.COM X2

Adultmothsandtheircaterpillarsaremasters
ofmasquerade.Excrementis justoneofa host
ofunpalatablethingsthattheyreplicate,from
deadleavestolichen,twigs,barkandstone.
MacrocilixmaiaofsouthernAsiarecreates
anentirescene:theadultmoth’sopenwings
suggestnotonlyfreshlydribbledbirdpoo,but
alsotwovisitingflies, complete with wings, legs
andredeyes.
HowonEarthdoessuchmind-boggling
trickeryevolve?“Birdshavebettercolourvision
thanwedo,”saysSkelhorn,“andtheycan
makeoutfinerdetail.Sotofoolthem,there’sa
strongselectionpressure.Overtime,yougetthe
evolutionofperfection.”However,hecautions
thattheremayalsobesomeothertrade-offgoing
on.There’sbeenlittleresearchsofarintothis
species,andtheremightbeotherevolutionary
reasons– apartfromdeception– forwhyM.maia
has developed this impressive wing pattern.

“Therearemanywaysforspiderstolookunspidery,”says

Goodacre,butimitatingpoois somethingatwhichthey

excel.Worldwide,severalgroupsofspiderarevirtuosofaeces

mimics,shesays.“Theyclearlyhavethegeneticarchitecture

tomasquerade.”Thissubterfugecaninvolvea suiteofphysical

adaptations,forexample,adopting the size, colour, texture and

patinaofbirddroppings.

Somespecies,suchasSoutheastAsia’sPhrynarachnedecipiens

(picture1, opposite) andP. r ugos a( 2 ) ofAfrica,heightenthe

illusionbygivingoffthewhiffoffreshdroppingsandweavinga

messywebaroundthemselves.Poo-mimickingspidersalsoretract

theirlimbs,changingtheirsilhouettetoanamorphoussplodge.

AsGoodacresays: “Extended legs are a giveaway, but you can fix

thisforfree.”

Theabilityofpoo-mimickingspidersservesdifferentusesin

differentspecies.Celaeniaexcavata( 3 ) is a nocturnalmoth-hunter,

whosecamouflageseemstobea daytimedefencefrompredators

suchasbirds.Arkyscurtulus( 4 ), ontheotherhand,huntsbyday

andappearstousepoo mimicry aggressively, to lure dung-loving

flies to their doom.

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STILL LIFE

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SPOOF SPIDERS