The Stick Insects of Southwest England
Many people don’t know this, but Cornwall, Devon and the Isles of Scilly have a thriving stick insect population. They have been living wild in the south-west of the UK for over 100 years, but as they’re well known for their amazing ability to camouflage into their surroundings you may not have seen them even if you do live in the area. I became enchanted with stick insects as a child, and the more I learn about them the fonder I become. They’re fascinating little critters to watch!
There are now 5 known naturalised species in the UK.
This means that they both live and reproduce here. You might be thinking this is a bad thing – invasive species usually are – but unlike many introduced species they appear to have no detrimental effect to other native insects or plants. The majority of UK naturalised stick insects originate in New Zealand, though there are also smaller numbers of two species from southern Europe. The likely cause of the introduction of stick insects to the UK is the importation of plants, unknowingly bringing eggs to the UK that manage to survive in the south-west due to the mild winters.
The Unarmed Stick Insect (Acanthoxyla inermis) accounts for most of UK records (around 60%), with the majority of sightings being in Cornwall. There are also established colonies in Devon, particularly in the Plymstock area, and even some further east in Dorset. It has been here since the early 20th century, with records at Treseder’s Truro nursery in the 1920s. They are the longest UK insect.
The Prickly Stick Insect (Acanthoxyla geisovii) is a New Zealand species mostly found in the St. Mawes area of Cornwall and the Torbay area of Devon, as well as being prevalent on the Isles of Scilly. The first recorded sighting was that of a prickly stick insect in a Paignton garden in 1909. Another sighting happened on the Isles of Scilly in 1943 at Tresco. It is thought that both colonies may be as old as each other as in 1907 tree ferns were imported from NZ onto Tresco gardens, and in the same year, some of these were sent on to Paignton.
The Mediterranean Stick Insect (Bacillus rossius) has been reported in Hamsphire and the Isles of Scilly. The Hamspire colony is known to have existed since 2009, whilst the Isles of Scilly one was located in 2002.
The White’s Sicilian Stick Insect (Bacillus whitei) is similar to the Mediterranean Stick Insect and there are reported colonies in gardens in Slough occuring since the 90s. Like the Mediterranean species this one originates in southern Europe.
The Smooth Stick Insect (Clitarchus hookeri) is another New Zealand species. It was first reported in 1949 is only found on the Isles of Scilly.
Of course, if you come across a stick insect in the UK it could also be an escaped pet, with many reported sightings being what is known as a laboratory stick insect as these are the most readily available in pet shops. Unable to survive our winters, you may still spot recent releases in the warmer summer months. Many exotic pet stick insects won’t survive outdoors in our climate.
If you’ve ever watched a stick insect you will have noticed them doing at least one of two things. They’ll be perfectly still, not moving at all, or swaying from side to side. The swaying movement helps them imitate a plant in the wind, more effectively selling their camouflage and protecting them from potential predators.
Their family name means Phantom!
Stick insects belong to the family Phasmatodea, or Phasmid, which according to Wikipedia is “derived from the Ancient Greek φάσμα phasma, meaning an apparition or phantom”. This is a reference to them so closely resembling sticks or leafs they live upon.
It’s thought that all those living in the UK are female.
They’re a proper little Amazonian society! A number of stick insect species are able to reproduce parthenogenically, without the use for men. Females that haven’t mated with a male will produce more female eggs, and so it will continue. There are even species of stick insect where no males have ever been discovered! The Unarmed stick insect that has made its home here appears to be one such species.
Their eggs look like tiny seeds.
Not only do they mimic plant life, their eggs do too! The seedlike appearance of them means that carnivorous predators are less likely to pay them any attention. Their eggs drop from their abdomen scattering across the floor much like dispersed seeds. In the wild ants will often carry the eggs to their nests where they will feed on a fatty capsule known as the capitulum without damaging the embryos. The eggs will remain in their nest, being kept much warmer than had they been left on the floor.
The eggs can take anywhere between weeks to months to hatch, depending on both species and habitat. Once hatched, the nymphs grow by moulting. They’ll shed their skin numerous times before reaching adulthood. Generally they’ll eat the moulted skin. This helps recycle the protein, but also protects them. They are at their most vulnerable just after moulting, before they harden again, and having the shedded skin next to them in the wild is a big giveaway to predators.
Nymphs can shed and regrow limbs, a process that helps them escape predators. The lost limb will usually grow back shorter than before however.
Some stick insects change colour!
Just like chameleons, some species have been observed altering their colouring to help sell their camouflage even more.
Other defence mechanisms include the ability to lose limbs and regenerate them during the adolescence. Limbs are regrown with a moult, so once they reach adulthood they are no longer able to do this. Some species (none of which are naturalised in the UK) can release varying chemical compounds with a variety of effects. Some species will release a strong odor whilst others will cause a burning sensation in the mouths and eyes of potential predators. Other species will flash bright colours or curl their bodies up, mimicking scorpions, to ward off anything looking to have them for lunch.
For years I’ve been saying that I want to get some, so when a young one recently landed on my mum’s arm in the garden I couldn’t resist bringing her in. I don’t know why she’s called Darcey and I’m still not sure where the name came from, it just popped into my head and makes me smile almost as much as she does. Like many of the names of wildlife that regularly visits the garden, it came out of nowhere and seems to have stuck.
I don’t know enough to be able to hazard a guess at whole old she is, but I’m pretty certain she’s an unarmed stick insect as it’s a species we’ve had multiples of here before. Her favourite food is definitely brambles, and since having her she’s already moulted once! That’s actually her skin you can see beside her in the picture above, which she ate shortly after. Tasty!
She’s still quite small so for the minute I’ve got her in a large storage box with netting instead of a lid. It’s plenty big enough for her right now, but she’ll need a larger place soon. Stick insects hang upside down from the roof of their habitat to moult and as such need quite a tall home at least 3 times the length of their body in height.
She’s the first insect I’ve ever kept (beyond those that have just moved into the house), so I’m excited to learn more as I keep her and have been reading up as much as I can. I’d love to hear from anyone who has kept Unarmed Stick Insects as I’m yet to find any information about this particular species being kept as pets, though I’m sure many have.
“What should I do if I find a stick insect in the wild?”
Take a clear photograph to help with identification. Then report to the UK Phasmid Study Group to help gain a better idea of what stick insects are living in the UK and where. Unless it looks like it’s in any immediate danger please leave it where it is. Avoid handling unless absolutely necessary, they are fragile!
Despite doing so myself, I wouldn’t recommend capturing one and keeping it as a pet unless you have prior knowledge. Whilst they’re pretty easy to look after, you should never take on a pet without first knowing as much as you can about their requirements as a species. I’ve spent a long time researching the stick insects that have made themselves at home in this country and spotted many before eventually bringing Darcey in.
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