Common Stick Insect

Yes. The common (Indian) stick insect reproduces almost entirely by parthenogenesis, meaning females produce viable eggs that develop without being fertilised, and those eggs hatch into more females. Males do occur very rarely — perhaps one in a thousand or fewer — and appear to contribute little or nothing to reproduction; the all-female laboratory strain kept in classrooms around the world has been maintained since the early 1900s without any males at all. This makes the species extremely easy to culture — a single hatchling raised alone will grow up and lay dozens to hundreds of fertile eggs. Some other stick insect species reproduce sexually, some switch between the two modes, and a few consist only of females.

Its primary defence is looking exactly like part of a plant. The body is long, thin, brown or green, and often textured with tiny bumps and ridges that mimic buds and thorns, and at rest the insect holds its front legs stretched straight forward alongside its head so the whole animal reads as a single twig. It stays motionless by day. If a breeze stirs the foliage, or if something touches it, the stick insect sways rhythmically, matching the movement of the real branches around it. Beyond mimicry it has backup options — it will drop from the plant and lie rigid and still ("playing dead"), it can shed a seized leg and escape, and if picked up it may curl its abdomen up in a scorpion-like bluff. Some larger relatives flash bright hindwings or spray irritant chemicals, but the common stick insect relies mostly on disguise.

The common stick insect is a classic beginner invertebrate — cheap, hardy, quiet, odourless, and needing only a ventilated tank, a jar of fresh bramble or privet, light misting, and room temperature. Handling is possible if done slowly and low over a soft surface, since a startled insect may drop and could lose a leg. The main responsibility is preventing escape and never releasing them or their eggs outdoors. Because they breed so readily without mates and eat common hedge plants, released stick insects can establish wild populations outside their native range — which has already happened in parts of Europe — so in some countries, notably the United States, keeping or importing non-native stick insects is restricted or requires a permit for exactly this reason.

The eggs of many stick insects, including this one, closely resemble plant seeds — they are hard, rounded, and patterned — and they carry a specialised fatty cap called a capitulum on one end. This is chemically and structurally similar to the elaiosome, the oil-rich appendage that plants like violets and trilliums put on their seeds to bribe ants. Foraging ants pick up the stick insect eggs, carry them back to the nest, eat the nutritious cap, and discard the still-viable egg in the colony's waste chambers or nearby. There the egg is sheltered underground from predators, parasitic wasps, fire, and drought until it hatches, and the tiny nymph climbs out and heads for the nearest foliage. It is a genuine case of an insect mimicking a plant's seed-dispersal strategy.