The strongest web in the world is that of female Darwin’s bark spiders

In the forests of Madagascar hides the Darwin’s bark spider (Caerostris darwini), a natural “engineer” famous for weaving the cobwebs toughest on the planet. These structures, long too 25 meters and wide up to 2.8 square metershave been found suspended above rivers and are made of silk ten times stronger than Kevlarthe material of bulletproof vests. However large they are, they are nothing compared to the spider’s web collective giant – produced by more spiders – than 100 m² recently discovered in a European cave.

A new study published in Integrative Zoology demonstrated that the ability to produce this “invincible” material is not common to the entire species, but is exclusive to adult females Of C. darwiniprobably to allow them to capture larger prey given the accentuated sexual dimorphism, females are on average 3 times larger than males. The bark spider was first described in 2010 and owes its name to Charles Darwin given that its discovery in Madagascar in 2009 coincided with the 150th anniversary of “The origin of the species“. Furthermore, the body is characterized by irregular colors between black, brown and grey, reminiscent of tree bark and making it a master of camouflage.

The strongest web is produced by female spiders Caerostris darwini

One of the most obvious features of C. darwini is the presence of important physical and functional differences between males and females, the so-called sexual dimorphism. Females are very large compared to males. A female’s body measures between 18 and 22 millimeters (excluding legs) is about 3.1 times larger than the tiny males, often less than 6 millimeters. This size disparity plays a crucial role in the reproductive behavior and, as we will see, also in the engineering capabilities of the species.

A recent study published in Integrative Zoology has added a new piece to the already complicated biology of these animals, revealing that “super-silk” is not a gift shared equally among all specimens of the species. The researchers analyzed the mechanical properties of silk produced by adult females and males, females and young males, discovering a substantial difference. Silk from extreme resistance it is produced only by adult females both in Caerostris darwini that in Caerostris Kuntnerianother species from Madagascar.

Males and young specimens form a silk with much lower mechanical characteristics, comparable to those of other common spiders. Why this difference? The hypotheses put forward by the authors of the study concern the selective pressure linked to the different body dimensions between the two sexes. The larger, tougher structures built by adult females may be key to catch catches bigger and faster like dragonflies, a need that smaller males do not have as they can feed on smaller insects. Furthermore, the eldest extensibility it could prove to be an adaptation to the river environment, necessary to build the canvases suspended above the water. Studying these fabrics and how they are produced in depth could provide new information for the synthesis of stronger synthetic fibres.

What are these webs made of, tougher than Kevlar

The bark spider, in addition to being a skilled “engineer” of nature, is also a record breaker. Its orbicular spider webs (wheel) are the largest in the world: 25 meters in length, thanks to “bridge” structures that also extend over rivers and lakes, with an area that can go up to 2.8 square meters. The reasons why spiders build webs are to hunt flying insects, build egg cases, and make their own shelters.

This super-strong architecture is only possible thanks to the material the webs are made of. Spider silk, apparently delicate and impalpable, is a fiber with extraordinary properties, generally made up of proteins called spidroine. However, that of the Darwin’s bark spider has its own particular composition which makes it twice as tenacious as any other spider silk and well ten times stronger than Kevlarthe synthetic fiber used for bulletproof vests.

In the silk of C. darwinicall draglinesin addition to two common proteins there is a silk protein called MaSp4rich in prolinean amino acid that improves the elasticity of silk. This robustness is essential for resisting atmospheric events such as wind and rain and for absorbing the kinetic energy of flying prey.