Spiders play mahjong? This little spider throws a four-piece card at you!

What is March 14th? White Day? Pi Day? Not only that, it's also Save A Spider Day.

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There are spiders in the pictures in this article, so friends with arachnophobia please read with caution

Speaking of spiders, many people will feel creepy, but there are also cute and protected species in the spider family, such as the jumping spider, whose eyes account for the largest proportion of its body, and the Hainan bird spider (Cyriopagopus hainanus), the only spider under national second-level protection.

Peacock jumping spider will "spread its tail"｜Colorsoffauan / tumblr

But in my opinion, the less famous Chinese spiders, such as the humphead spider, combine these two characteristics. They look cute, with "four-barrel" patterns on their bodies, but they are not like Spider-Man who can save the world - on the contrary, they are waiting for human salvation.

Oops, I put the wrong picture. Click on the picture below to see the cute spider cake｜Affemitwaffe / Wikimedia Commons

The "four barrels" in the spider

The velvet spider is a small family of spiders. There are currently 9 genera and 102 species known worldwide. The most representative spider is Eresus kollari. In English, male and female spiders are collectively called velvet spiders, which refers to their silky, short tentacles that cover their bodies. People who have touched one say that it is unforgettable. It is no exaggeration to say that it is the silkiest spider I have ever touched.

The male Coe's head spider also has an English common name of Ladybird spider. It is not difficult to guess the origin of this English name by looking at the pattern of the male. In China, it is called the four-pancake spider or dice spider. In popular science books in Europe, the figure of the Coe's head spider with high appearance often appears.

The picture below is the ID photo of the Koch's spider (male on the left and female on the right) | Jiang Tongyao

The Cochlear Wretch is one of the most widely distributed spiders, found from Europe to northern China. It prefers dry habitats, is extremely sensitive to environmental changes and human disturbance, and requires plants for camouflage, so it generally lives in dry, warm wastelands with natural complex vegetation. The high requirements for habitat make the Cochlear Wretch a suitable indicator of environmental quality.

Black and Red: Go away, I'm not tasty!

The Coeur's head spider is black before it reaches sexual maturity. When it becomes an adult, the male will turn into a bright red color similar to that of a ladybug, while the female's color remains dull. This is because females usually dig holes to live in, and the black color helps them to "hide" in the darkness of the hole and be difficult to be discovered. Males hunt and hunt everywhere, while looking for females at the same time.

From the moment a male crawls out of the den to hunt, he is at great risk of being preyed upon, and this is when the black and red color combination comes in handy. For many predators, the black and red combination is a signal that the prey may be poisonous and unpalatable. When the color is not enough to scare off the opponent, the male will raise his abdomen, display colorful patterns, and shake his legs to intimidate the opponent.

A male Coeur's ramblers on the hunt | Lin Yejie

The females will dig a 5-10 cm deep inclined silk tube under the rocks to live and hide. The inner wall of the silk tube is woven with fine spider silk, which is soft and comfortable; the funnel-shaped tube mouth is stuck with dead grass and fallen leaves, and there are relatively fine radial silks to catch passing prey.

The female spider's silk nest is covered with a thin layer of silk. Photo by R. Rozwałka | Robert Rozwałka et al. / Acta Zoologica Bulgarica (2019)

It is worth mentioning that the reason why the spider silk of the big-headed spider can stick to its prey is not through mucus, but through the highly elastic filaments secreted by the sieve apparatus specialized from the spinning apparatus. This kind of silk contains one or two straight axes, accompanied by several curved supporting lines, covered with very fine (20 to 30 nanometers) spider silk. When it comes into contact with the prey, it will generate van der Waals force to stick to the prey.

The yellow glasses-shaped area is the sieve organ, which is an important identification structure in spider classification | Lin Yejie

When they haven't eaten for a long time, they will leave the web and hunt nearby. Basically, they will prey on any animal that can be caught in the web. They eat whatever is distributed locally. Some scientists investigated the remains in the spider web and found that their food includes almost all common arthropods in the local area: centipedes, millipedes, grasshoppers, ants, flies, beetles, spiders, etc.

Natural enemies: They only target unmated females

When preparing to breed, the male Coeur's bump spider will seek out a high place, then swing the first and second legs to detect female pheromones, thereby finding a sexually mature female. When he encounters a female's nest, he will go in and live with the female for a period of time and mate. After a few weeks, the female will seal the opening of the silk tube and lay eggs in it.

The reproductive behavior of the Coeur's bump spider is also very special: the bump spider is one of the few spiders that have the behavior of raising their young. On sunny days, the female will move the egg sac to the opening of the silk tube to heat up the eggs and accelerate hatching. After hatching, the spiderlings eat the food vomited by the female spider.

When the female dies naturally, the spiderlings will feed on the mother's body and use it as stored energy to hibernate in the nest. In the spring of the following year, they will leave the silk tube and start their own business. At this time, the spiderlings are already quite large and the survival rate is greatly improved. The growth of the humphead spider is slow, and females need three to four years to mature. Males only need one year. This habit may be to prevent inbreeding.

A. corymbose spider in its natural habitat | Damian Trzybiński / Wikimedia Commons

Such a low-key life does not mean that the Koch's bump-headed spider can sit back and relax.

Green woodpeckers or crows will pull out their tubes and tear them apart, find the spiders and eat them. There is also an obligate parasitic spider wasp (Eoferreola rhombica), which specifically seeks out unmated adult females (mated females will seal the tubes), enters the tubes and attacks the spiders, paralyzes them with venom, and then lays eggs on them. The hatched larvae feed on the paralyzed but still alive bump-headed spiders.

Spider wasps lay their eggs on paralyzed spiders, and their larvae feed on the spiders | Lex Peeters & Ivo Raemakers / Natuut.focus (2011)

Most spider larvae can spread by spinning silk and floating in the air. However, the larvae of the Coeur's bump spider are already too heavy to fly when they leave the nest. When habitats are destroyed and fragmented due to human disturbance, fires, and other factors, the Coeur's bump spiders will be trapped and slowly die. Even if the habitat is restored after a period of time, it will be difficult for the bump spiders to return and settle again.

The habitat of the Crassula sutchuenensis, with a driving training ground next to it | Lin Yejie

Because the environment where the Corythuja sylvatica lives highly overlaps with the pasture environment and is often developed for grazing, this means that without human help, their habitat will only continue to shrink, compress, and even disappear.

In Europe, many species of bump-headed spiders are facing the above threats, and local conservation agencies have used them as flagship species to promote habitat protection. There are also populations of bump-headed spiders in China facing similar situations. I hope that this beautiful and lovely spider will be valued and protected like rare birds and animals in the future.

Author: Lin Yejie

Editor: pee pee shrimp

This article comes from the Species Calendar, welcome to forward

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