Plasticity in an extended phenotype and reversed up-down asymmetry of spider orb webs

► Orb webs have larger lower part but this size asymmetry is sometimes reversed. ► I examined whether plastic web-building behaviour is related to asymmetry reversal. ► Spiders plastically elongated web downwards when fed in lower web part. ► They did not elongate web upwards when fed in upper web part. ► This suggests plastic web asymmetry does not always lead to asymmetry reversal.