An electron microscopy image of the silk of the Australian net-caster spider, Asianopis subrufa, has won top prize in the Royal Society Publishing Photography Competition

Spider silk threads

Source: © Martín Ramírez

The image was captured by arachnologist Martín Ramírez at the Bernardino Rivadavia Natural Sciences Argentine Museum in Buenos Aires, who first had to coat the silk with a mixture of gold and palladium to visualise it under the microscope. The electron micrograph is just 50µm in width and was taken using a field-emission scanning electron microscope under high vacuum.

The net-caster spider catches its prey by spinning a sticky silk that it holds between its four front legs. When an insect nears the spider it can cast its stretchy net over its prey, entangling it. This extension of the threads when cast is made possible by the stretchy elastomeric core of the silk, which is sheathed in a layer of harder fibres that strengthen it.