The web of an orb-weaver spider is a giant sensory organ, a deadly trap, an architectural wonder, and a spectacle of elegance. Members of this group build large, intricate, concentric webs using a toolkit of different special-purpose threads produced from their three or four sets of spinneret glands. The support and radial lines, made of non-sticky, stiff strands, are spun first; then, the highly elastic, glue-coated, arc-shaped strands, that spiral outwards from the centre. Being extremely thin (ranging from tens of nanometres to a few micrometres), spider silk appears very delicate, but the relative tension required to break some spider silks is far greater than for some steels.
Using the web as an extended sensory organ, the female spider, resting head-down at the centre of the orb, awaits tell-tale vibrations. If it’s an insect that has blundered into the web, she rushes to wrap it in even more silk; several metres of thread will bind and immobilise the victim, and also package it neatly for a later meal. If it’s a male spider that has decided to romance her – males can be as small as one-tenth the size of females – he must tread the threads with caution, making only the most precise moves as he shakes and taps the web. Every species has its own rhythm, and the courting male has to get his percussion act right, or risk being mistaken for prey; there are no retakes! If she chooses love over food, she plucks the threads to say come-hither in spiderspeak. The male then spins a special mating thread, fastening one end to the female’s web, and the other to a nearby support such as a plant stem. The female climbs onto the mating thread, and hangs motionless. Carrying sperm on his pedipalps that look like boxing gloves, he proceeds to deposit it in her genital opening. Courtship thus leads to copulation, and sometimes, cannibalisation (more on fatal spider love in some other blog), on a silken thread.
Research continues to bring to human awareness how spiders produce and use one of the toughest known biomaterials. Recent findings throw light on how one group of spiders crushes its prey by excessive wrapping; one species was recorded to shroud its victim in 140 metres of silk, compressing the insect with such force that its legs broke and its eyes buckled inward.
Advances in transgenesis have made possible the breeding of goats that can produce large quantities of spider silk protein in their milk. Though not without their share of ethical concerns, these developments are opening up the possibilities of using spider silk to repair damaged nerves, tissue, and even broken bones.
So, on your next walk in the woods, if you come across a spider web, take a mindful moment to stand and stare at the critter and her creation. They hold the cure to many a malady.
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About the Author: Rizwan Mithawala is a Conservation Writer with the Wildlife Conservation Trust and a Fellow of the International League of Conservation Writers.
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Disclaimer: The author is associated with Wildlife Conservation Trust. The views and opinions expressed in the article are his own and do not necessarily reflect the views and opinions of Wildlife Conservation Trust.
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