The common walkingstick, Diapheromera femorata, is a plant-eating insect native to North America whose elongated, twig-like body makes it one of the most effective camouflage artists in the insect world. Found primarily in deciduous forests across the eastern United States and southern Canada, it belongs to the order Phasmatodea, a group of over 3,000 species worldwide that have independently evolved body plans mimicking sticks, leaves, and bark. But the common walkingstick is far more than a passive impersonator of dead wood. Its biology includes some genuinely surprising features, from eggs that look like seeds to a digestive system that works differently from most other plant-eating insects.
More Than Just Looking Like a Stick
The most obvious thing about a walkingstick is its shape: a slender, cylindrical body with long, thin legs that fold against it to complete the twig illusion. Adults of the common walkingstick typically measure around 7 to 10 centimeters, with females noticeably larger than males. Their coloring ranges from green to brown depending on age, sex, and environment, and they spend most of their time motionless on branches, which makes them remarkably hard to spot even when you know they are there.
But shape and stillness are only part of the deception. Many stick insects also sway gently back and forth, and research on a related species showed this behavior is triggered by wind. In wind-present trials, the vast majority of insects swayed, while none did so when the air was still. When researchers compared the motion signatures of swaying insects with those of surrounding plant material blowing in the breeze, the two were statistically indistinguishable. A motionless insect on a moving branch, by contrast, stood out sharply from its background.1Oxford Academic (Behavioral Ecology). The swaying behavior of Extatosoma tiaratum: motion camouflage in a stick insect? The takeaway is counterintuitive: sometimes the best way to stay hidden is to move, as long as you move the way everything around you is moving.
Dropping a Leg to Save Your Life
When camouflage fails, walkingsticks have a backup plan that sounds drastic but works well: they can deliberately shed a leg. This process, called autotomy, is a voluntary response to being grabbed by a predator or getting stuck during a molt. The insect simply releases the leg at a pre-formed breakpoint, and the predator is left holding a twitching limb while the insect escapes.
What makes this more than a one-time sacrifice is that younger walkingsticks can regrow lost legs. Research on the twostriped walkingstick found that a leg dropped during the second nymphal stage goes through a predictable regrowth sequence over subsequent molts. After the first molt following the loss, the replacement leg is roughly one-quarter of its normal size. After the second molt, it reaches about half. By the third, it is close to full size.2Annals of the Entomological Society of America. Leg Regeneration Trade-Offs in the Twostriped Walkingstick (Phasmatodea: Pseudophasmatidae) That regrowth is not free, though. In a related species, regrowing a leg during development led to disproportionately smaller wings in adulthood and worse flight performance, meaning the insect pays for its escape with reduced mobility later in life.3PubMed Central. Leg regeneration stunts wing growth and hinders flight performance in a stick insect (Sipyloidea sipylus) Adults that have already reached their final molt cannot regenerate, so a leg lost late in life stays lost.
Chemical Warfare in a Relative
The common walkingstick itself is harmless to people, but one of its North American relatives is not. The twostriped walkingstick, Anisomorpha buprestoides, is found throughout the southeastern United States and has a defensive spray that it aims directly at the eyes of perceived threats. This spray can cause real ocular injury in humans, with reported cases ranging from conjunctivitis to corneal ulceration.4PubMed. Twostriped Walkingstick Targets Human Eye With Chemical Defense Spray
The active ingredients in this spray are monoterpene dialdehydes, and researchers have identified at least three different forms produced by A. buprestoides, with the particular mix varying by geography and developmental stage.5PubMed. Developmental and geographical variation in the chemical defense of the walkingstick insect Anisomorpha buprestoides The spray is effective against insects, birds, and mammals alike, and the insect can aim it with surprising accuracy over a distance of several inches. People who encounter twostriped walkingsticks in Florida or the Gulf Coast sometimes mistake them for the harmless common walkingstick and handle them, which is when the spray becomes a problem. If you get hit in the eye, flushing with water and seeing a doctor is the practical advice.
The common walkingstick has no such spray. Its defense repertoire is limited to camouflage, stillness, leg-dropping, and occasionally falling off a branch and playing dead on the ground. It is entirely safe to handle.
What They Eat and How They Digest It
Common walkingsticks are strict herbivores, and their diet shifts as they grow. Young nymphs feed on the leaves of various understory shrubs and small trees, while older nymphs and adults show a strong preference for oaks and cherries.6Journal of Applied Entomology. Biology and ecology of the Northern walkingstick, Diapheromera femorata (Say) (Phasmatodea: Diapheromerinae): A review They feed mainly at night and can consume a surprising amount of foliage for their size, which becomes ecologically relevant during outbreaks when their numbers spike.
How they process all that tough leaf material is genuinely unusual. Most herbivorous insects rely on gut bacteria to help break down plant cell walls. Termites, for instance, are famously dependent on their gut microbiome. Walkingsticks appear to work differently. Analyses of the stick insect gut have found that these insects are unlikely to depend on bacteria for digestion and instead produce their own enzymes to break down plant cell walls, a task that most other herbivorous insects outsource to microbial symbionts.7PubMed Central. Analysis of the gut microbiota of walking sticks (Phasmatodea)
A more detailed review of stick insect gut anatomy confirmed this picture: the phasmid gut lacks the specialized structures, like enlarged fermentation chambers, that other plant-eating insects use to house their bacterial partners. Recent genetic work has shown that stick insects produce their own plant-cell-wall-degrading enzymes in certain sections of the gut, which would theoretically let them digest cellulose without microbial help. That said, the story may not be completely settled. One intriguing finding is that stick insects fed monoterpene-rich eucalyptus leaves consistently harbor a bacterium called Serratia marcescens, which is known to break down monoterpenes. Researchers have hypothesized that this microbe helps those species tolerate the chemical defenses of their host plant, which would explain how they can strip so many eucalyptus leaves during outbreak years in Australia.8Journal of Orthoptera Research. Review of the Gross Anatomy and Microbiology of the Phasmatodea Digestive Tract So while walkingsticks are largely self-sufficient digesters, they may still benefit from microbial help when eating particularly well-defended plants.
Eggs That Look Like Seeds
Walkingstick reproduction has some features that seem designed to confuse anyone trying to study it. Females of the common walkingstick simply drop their eggs one at a time from wherever they happen to be in the canopy. The eggs tumble to the forest floor and land in the leaf litter, where they sit through the entire winter and hatch the following summer. There is no nest, no egg mass, no parental care of any kind.
The eggs themselves are small, hard-shelled capsules that bear a striking resemblance to plant seeds. This is not coincidental and has been recognized by researchers for over a century. Each egg has a small cap-like structure called a capitulum, and in some stick insect species, this cap mimics the fatty, nutrient-rich appendages found on certain seeds. In at least one Neotropical species, ants pick up the eggs and carry them underground to their nests, attracted by the seed-like cap, just as they would carry actual seeds. The ants eat the cap and discard the rest of the egg in their waste chambers, which happen to provide warm, moist, protected conditions ideal for the egg to develop in.9Springer Link / Journal of Insect Behavior. The egg capitulum of a neotropical walkingstick, Calynda bicuspis, induces aboveground egg dispersal by the ponerine ant, Ectatomma ruidum Whether this ant-mediated dispersal plays a role for the common walkingstick specifically is less clear, but the seed mimicry of phasmid eggs is widespread across the order.
The timing of hatching is controlled by a dormancy period called diapause, and research on Asian stick insect species has shown that this timing is regulated by a combination of temperature conditions experienced by the egg and the light conditions experienced by the mother before she laid it. Eggs kept at moderate temperatures hatched after more than a hundred days, but the mother’s exposure to short versus long day lengths significantly shifted when her offspring emerged.10European Journal of Entomology. Effects of environmental factors on the regulation of egg diapause in the walking-stick insect, Ramulus irregulariterdentatus (Phasmatodea: Phasmatidae) A more recent study on a different species confirmed that early embryonic diapause is regulated by the combined effects of maternal day-length exposure, the mother’s age at the time of egg-laying, and the temperature the egg experiences after being laid.11Journal of Insect Physiology. Maternal photoperiod, age, and egg temperature regulate early embryonic diapause in the stick insect, Phraortes elongatus This multi-factor system helps ensure that eggs hatch in spring when fresh foliage is available, rather than during an unseasonable warm spell in late autumn.
For the common walkingstick specifically, eggs overwinter in the leaf litter and begin hatching in mid-June, typically during evenings when ground-level humidity rises above about 80 percent. Around 90 percent of the hatch is usually finished by the second week of July.12Forest Science. Ecology of the Walkingstick The nymphs then climb into the canopy and begin feeding.
When Walkingstick Numbers Explode
Most years, common walkingsticks exist at low enough densities that you would never notice them. But populations can occasionally boom into outbreak levels, and when they do, the defoliation can be severe. Walkingstick outbreaks tend to hit oak-dominated forests hardest, and research has documented that severe defoliation by walkingsticks significantly reduces the radial growth of black oaks.13Forest Science. Ecology of the Walkingstick This matters because radial growth reflects how much energy a tree is putting into building wood versus just surviving, and repeated defoliation can weaken trees enough to make them vulnerable to drought, disease, or secondary insect pests.
Nymphs require roughly 1,835 accumulated day-degrees above a base temperature of about 9°C to complete their development from hatchling to adult. That thermal requirement means development speed is tied directly to summer warmth. In a cooler-than-average summer, development takes longer; in a warm one, it speeds up. This temperature sensitivity is part of why outbreaks are episodic rather than constant. A sequence of warm summers can accelerate development, increase survival rates, and allow populations to build quickly.
The common walkingstick has a two-year life cycle in the northern parts of its range: eggs laid in one summer do not hatch until the second summer after that, creating alternating even-year and odd-year cohorts that can be noticeably different in density. Forest managers in regions with a history of walkingstick outbreaks sometimes track which cohort is dominant to anticipate when defoliation might peak.
The Wing Question
One of the more interesting evolutionary puzzles about stick insects is their relationship with flight. The common walkingstick is completely wingless, and most stick insects worldwide are either wingless or have only vestigial wing stubs. For a long time, scientists assumed this was a straightforward story: the ancestor of all stick insects had wings, wings were lost as stick-like camouflage became their primary survival strategy, and that was the end of it. Losing complex structures is common in evolution; gaining them back is supposed to be vanishingly rare.
Except that is not what the phylogenetic evidence shows. A study in Current Biology presented evidence that wings may have reappeared several times independently within the stick insect order, despite the group’s ancestor being wingless.14PubMed. Evolution: have wings come, gone and come again? This finding challenged a principle known as Dollo’s Law, which holds that complex structures, once lost in evolution, do not come back. A more recent large-scale analysis reinforced this picture, finding that wings were lost or reduced in the lineage leading to the ancestor of all living stick insects, but that partial or full wings subsequently re-evolved in multiple descendant lineages. The same study found that intermediate wing states, where an insect has small wings that are too short for flight, tend to be evolutionarily unstable unless those short wings have been repurposed for non-flight functions like startle displays or sound production.15PubMed. Macroevolutionary Analyses Provide New Evidence of Phasmid Wings Evolution as a Reversible Process
The implication is that the genetic machinery for building wings was never fully erased during the long wingless period. It was silenced but apparently remained intact enough to be reactivated when selection pressure favored flight again, perhaps in lineages colonizing new habitats where dispersal mattered more than camouflage. The common walkingstick, for its part, remains firmly in the wingless camp. Its survival strategy is built around not being seen, not flying away, and dropping a leg if all else fails.
Keeping Walkingsticks as Pets
Stick insects are among the most popular pet invertebrates worldwide, and the common walkingstick is one of the easier species to keep. They need a tall, well-ventilated enclosure with fresh leaves from their preferred host plants, typically oak or wild cherry for D. femorata. Misting the enclosure lightly provides the humidity that helps with molting. They do not bite, do not spray (unlike their twostriped relative), and are slow-moving enough that handling is straightforward.
One practical issue that catches new keepers off guard is egg management. A single female can drop dozens of eggs over her adult life, and because the eggs look like tiny brown specks, they are easy to miss in the substrate. Without temperature manipulation to break diapause, eggs from temperate species like the common walkingstick may not hatch in captivity at all, or they may hatch unexpectedly a year or two later. Keepers who want to breed them typically collect the eggs and refrigerate them for several months to simulate winter, then bring them to room temperature and keep them humid. Success varies, partly because the maternal and environmental cues that regulate diapause timing are hard to replicate precisely in a plastic container on a shelf.
Tropical stick insect species, which skip the diapause step entirely, are generally easier to breed in captivity and are more commonly available in the pet trade. The Indian stick insect and various Australian species are popular choices. Some of these can reproduce parthenogenetically, meaning females lay viable eggs without mating, which simplifies things further but can lead to population explosions in a terrarium if you are not paying attention.