The Discovery of the World's Longest Insect: Crawling "Tree Branches"

On September 16, 2017, I received a certificate from Guinness World Records. It said "The longest insect is a stick insect (Phryganistria chinensis), which measures 640mm with legs fully outstretched and was bred at the Insect Museum of West China in Chengdu, Sichuan, China as made public in August 2017."

This means that the species has been officially recognized by an authoritative international certification body and has broken the record for the longest insect out of the 807,625 species of insects that have been discovered by humans (as of September 28, 2015).

The Chinese name for this sensational insect species is the "giant Chinese stick insect" (Latin name is Phryganistria chinensis Zhao). It belongs to the Phasmatodea order.

The world's stick insects are divided into five families with more than 300 genera and 3,000 species; China is home to more than 300 species of stick insects from 4 families. Most stick insects are long and thin and have 'nodes' resembling bamboo plants. The three pairs of slender legs also look like bamboo branches. This is why these insects are called 'bamboo-node insects' in Chinese.

If the stick insect's Chinese name is a vivid and direct description of its shape, then its Greek name 'phasma' is even more imaginative: it means 'phantom'.

Southeastern Asia has the most abundant number of stick insect species in the world. Many species are large in size, have an exaggerated appearance, strange colors, and are high in ornamental value. Insect lovers and collectors often aspire to obtain them.

The insect we are introducing here is the Phryganistria chinensis Zhao, which, at 64 centimeters long and a body length of 38.2 centimeters, is the largest insect specimen known to man.

For the origins of this giant bug, let me take you back to five years ago.

I went back under the street lamp to look at this giant bug in front of me. Its sawtoothed legs were like thorny branches, especially its forelimbs; the serrations were well-developed and neatly arranged like a saw blade. The body was roughly as thick as one of my fingers, brown with some green showing through. It resembled a tree branch but had a smoother texture.

It had an oval head. Its pair of round eyes looked clear and acute, and the two thin antennae were approximately 10 centimeters long, swaying in the cold night air…

The next day, I measured the size of this giant insect and I was very excited with the results: its body was 36.1 centimeters in length and the entire creature, including legs, was 62.4 centimeters long. The overall length and body length was 5.7 centimeters and 0.4 centimeters longer, respectively, than the longest recorded, Chan's megastick (Phobaeticus chani), as declared by the Natural History Museum in London. Obviously, this was the longest insect species ever discovered; not one of the longest, but THE longest!

After discussing with some authoritative Italian and German experts on stick insects, I confirmed that it was a brand new species. Since it was the largest stick insect species found in China, I named it the 'giant Chinese stick insect'. Its Latin name is Phryganistria chinensis Zhao, meaning 'Chinese'.

Even more fortunately, this stick insect produced six eggs after I brought it back to the Museum.The eggs were oval in shape, 5 mm long and 4 mm wide, relatively large for insects. The eggs were dark brown and exhibited fine streaks when dry. A small 'stalk' on one end makes them resemble small fruit.

The first egg hatched on January 5, 2015 under watchful care in the insect breeding room. The color of newly hatched larvae is completely different from that of adults. In this case, the color of the larvae was bright green, different from the adult's brown.

Its legs are even more special. They are completely different from other stick insects that imitate tree branches. Its forefeet are dark purple and the tips are white; its 4 back feet are intermittently purple and white. These bright colors make the insect stand out a lot. I guess this might be a warning coloration for birds so that they do not prey easily on the larvae, who can run as fast as ants.

Their growth gave me the opportunity to discover the secrets of this stick insect's entire life.

In mid-March, when outdoor temperatures in Chengdu had reached 20°C, I took them home and kept them in a large, 1.5-meter-high stainless steel insect cage on the terrace for easy observation. During several months, I observed their behavior almost every day. I found that during the daytime, they always choose to stay at the tallest branch or the top of the cage, hanging with their forelegs stretched straight and remaining stationary. Only after the sky turns completely dark that they begin to move.

Despite having saw-like spines on their legs, this "slow giant" does not have any offensive mechanisms. They avoid discovery by natural enemies using high levels of mimicry. Males imitate dead bamboo branches with their shiny, light brown bodies. The slightly thicker females look like branches. Their body color and markings change to adapt to the environments in which they grow up.

More importantly, it can be inferred that in the wild they live in tree tops and do not leave the canopy of the forest. Only at night are they lured away by bright lights. I guess they mistook lamplight for the moonlight and tried to make their way towards it for the night when I discovered them. In the forest, the moon shines on the highest part of a tree. This unique habit explains why such a gigantic insect had never been discovered before: it is impossible to find them from the ground when they hide in the lush crown, completely still and imitating branches.

The size of this insect gives us an opportunity to witness the magnificence of the microcosm. At least we know that some giant insects are still alive, even though many ancient giants have become extinct. We are lucky to have discovered it because in the past, large stick insect species were only discovered in countries close to the equator. This new species of giant stick insect found in China is a testament to the wonder of this land around us.

We plan to release the artificially bred individuals of this species back to its original place next year, hoping that they will be well protected in the wild and leave more wonderful species for our descendants.