Plant Harpoons

This lethal-looking weapon, just a couple of millimetres long, is the defensive weaponry deployed by a prickly pear cactus called Opuntia rufida. Most prickly pear species are armed with formidable spines that are several centimetres long and capable of drawing blood but this species has a surface ....

... covered with these small areoles - dense clusters of tiny, rigid hairs called glochids that are only loosely attached to the plant and ....

...... are easily dislodged by the slightest touch - or even by the wind. Those in this picture were gently brushed and you can see how they've broken loose. 

Each glochid is tipped with a sharp point (here magnified x100) that easily penetrates soft flesh like the lips and eyes of an animal attempting to eat the plant .....

..... and backward pointing barbs make it very difficult to remove. These microscopic harpoons are intensely irritating and potentially dangerous if they end up in your eyes, mouth or throat. The easiest way to remove them from skin is to use sticky tape to pull them out but if they end up in more vulnerable areas you may need hospital treatment. You can find medical advice here.


Opuntia rufida grows in arid parts of Texas in the United States. For more on prickly pears, click here.