Chien Lee / Twig Spider (Poltys elevatus) mimicking petiole, Sama Jaya Nature Reserve, Sarawak, Borneo, Malaysia

Piotr Naskrecki / Cycad (Cycas sp) trunks are covered with old leaf petioles, and special protective leaves known as cataphylls, South Africa

Chien Lee / Rufous Piculet (Sasia abnormis) on a spiny rattan petiole, Sepilok Forest Reserve, Borneo, Malaysia

Piotr Naskrecki / Cycad trunks are not covered with bark, but with remnants of the old leaf petioles, and special, protective leaves known as cataphylls, Modjadji Cycad Reserve, South Africa

Piotr Naskrecki / Acacia Ant (Pseudomyrmex flavicornis) collecting nectar from petiole at the base of Bullhorn Acacia leaf, Costa Rica

Konrad Wothe / Travellers Palm (Ravenala madagascariensis) petioles, Ranomafana National Park, Madagascar

Michael & Patricia Fogden / Cecropia (Cecropia sp) petiole with food for Ants (Azteca sp) which protect plant from herbivores in cloud forest, Tandayapa Valley, western slope of Andes, Ecuador

Michael & Patricia Fogden / Ant (Azteca sp) collecting food from Cecropia (Cecropia sp) petiole, in return, protects plant from herbivores in cloud forest, Tandayapa Valley, western slope of Andes, Ecuador

Doug Wechsler / Adult Hackberry petiole gall psylid (Pachypsylla venusta) on bark, Bucks County, Pennsylvania, USA. January.

Doug Wechsler / Adult Hackberry petiole gall psyllid (Pachypsylla venusta) emerging from gall, Philadelphia, Pennsylvania, USA. January.