Arachnophobia (afraid of spiders) is quite common and with good reason – such fear is deeply embedded in us and found to be hereditary.  

Arachnophobia  has a long history,  as early as the time of the birth of Christ parts of Abyssinia (officially Ethiopia) were abandoned by the whole population as a result of a plague of spiders.  Spiders rank with snakes, cockroaches and rats on the list of most  disliked creatures. According to some people, however, spiders are fascinating and often attractive animals, and like rats may have a purpose in the medical field.  

Spiders are the primary predators of insects, possess a venom system to assist in capturing prey and  produce and utilize silk in many more ways than any other animal.   About 13,000 of the known species manufacture webs.  

Anatomically, spiders are animals without backbones (invertebrates). They have two parts to their bodies, a cephalothorax (the head and thorax are fused together) and an abdomen. Eight legs and usually eight simple eyes are on the cephalothorax.  

Most spiders have teeth to chew an insect’s hard exoskeleton. Spiders then expel juices that liquefy their prey’s insides and allow them to be swallowed.

The evolution of myriad spider silks is reflected in the dazzling abundance of web types. All designs derive from a simple silk mesh used by ancestral spiders to line earth burrows more than 380 million years ago.  

Garden spiders can spin an orb web (a web with a spiral pattern) that is invisible to humans but visible to insects. Ogre faced spiders hang upside down from silk threads attached to branches.  There are also social spiders that work together to make extremely large webs that are attached to branches of trees and shrubs.  

By working together, social spiders can catch and eat insects may times larger than they are. Strangely, spiders do not become attached to their webs. Their legs feature a disengaging mechanism that enables the arachnid to detach itself instantly from a sticky strand.

Spiders are legendary as the materials-science experts of the animal kingdom.  They can produce as many as seven different kinds of silk. Silk from spiders is a protein fiber that has been the subject of intense research because of its impressive mechanical properties, including high strength and unprecedented toughness. The toughness of silk fibers is superior to any of the best synthetic high performance fibers available today.

To begin a web, a spider anchors a strand of dragline silk – three times stronger than the Kevlar used in bullet proof vests – and waits for a breeze to blow it to a second attachment point.  The spider then completes the outer ring and spokes and finally builds a spiral.   

Dragline silk is several times stronger than steel, on a weight by weight basis, but a spider’s dragline is only about one tenth the diameter of a human hair.

Dragline silk is a composite material comprised of two different proteins, each containing three types of regions with distinct properties.  One of these forms an amorphous (noncrystalline) matrix that is stretchable, giving silk elasticity.  When an insect strikes the web, the stretching of the matrix enables the web to absorb the kinetic energy of the insect’s flight.   Spiders are able to produce several mechanically distinct fibers from different silk glands.  

These different silks include dragline silk, which is stiff and strong, and capture silk, which acts like a very stretchy rubber.   The capture spiral in an orb web is stretchy and can triple in length before breaking.  Spiders use silk for a number of activities central to their survival and reproduction, including wrapping of egg sacks, preparing safety lines, lining retreats and most famously to capture insects.

Spider webs have been used as dressings for wounds and even as fishing nets, but the silk itself has found employment only as cross hairs in optical instruments.   This historical lack of use is about to change.  

As mentioned above, spider silk has the unusual combination of high strength and extensibility, characteristics unavailable in synthetic materials.  Now that there a greater understanding of the protein composition, the spinning process, chemistry and physical properties, and the genetic sequence,  it is more likely that silks will be used in a number of applications.

Molecular biologists plan to use the proteins from super strong dragline silk to build artificial tendons and ligaments and in improving the quality of microphones in hearing aids. The researchers needed more silk than they could harvest from spiders in captivity, so they genetically engineered goats to produce the proteins in their milk.  After the silk proteins are extracted and purified, a machine spins them into the needed fibers.

Final Thoughts

 To most of us spiders are vile creatures and we inherently fear them.  Scientists on the other hand are just beginning to discover how valuable spiders can be and precisely how they build their webs. Their creations bring new understandings of how creatures with brains a fraction of the size of human’s are able to create structures of such elegance, complexity and geometric precision.

Max Sherman is a medical writer and pharmacist retired from the medical device industry.  His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns.  He can be reached by email at  maxsherman339@gmail.com.