This is a stick insect. It is in the order Phasmatodea. I photographed this one at Playa las Mariposas on the Río Aguas Verdes in Perú on March 15, 2024. I wish every part of it were in focus, but photographing a gangly, swaying organism in dim light is challenging for me. Notice its large lower lip. The mandible is a key feature of Phasmatodea. Stick insects are herbivores. Their primary occupation is masticating plant matter. To avoid predators, adult stick insects are largely nocturnal. Their compound eyes are adapted to allow mature phasmids to move about and perceive details in the dark. 

I knew basically nothing about stick insects – or most insects for that matter – until recently when I assigned myself the belated task of learning the major orders of the class Insecta. My husband and quite a few friends are far ahead of me in their insect mastery. Where have I been? 

Phasmatodea is a relatively small order containing about 3,500 described species – compare that with Coleoptera, the beetles, with around 400,000 described species. But as a group they are very poorly known. According to this informative website https://phasmatodea.com/identification, entomologists who study phasmids are still struggling to correctly identify and organize all the genera and species. The obstacles are many: males and females of the same species, not to mention the nymphs, can look quite differently from one another; one species can be extremely variable in terms of morphological features such as coloration, size, body armature and camouflage. Add to these challenges the facts that phasmids disguise themselves as twigs and leaves, are nocturnal, and most species are found in the tropics, which are difficult, often remote environments to work in. It sounds like a Sisyphean task. The order is unlikely to be untangled until more molecular tools are used to identify species. 

Needless to say, there is no consumer demand for a field guide to the Phasmatodea, as wonderful as they are. There are a few guides in specific geographic areas where stick insects are relatively common, and where there is a critical mass of entomologists who study them, like Borneo. I will poke around from time to time in the phasmid literature online, but it is unlikely I will ever identify “my” stick insect to genus and species. That is just fine. I am happy I stumbled across this one, and as I am adapting to moving through the world more slowly in search of insects of all sorts, I hope to stumble on a few more.