Insects get a nasty surprise if they try biting into the leaves of bursera shrubs and trees: they use a sort of squirt gun to shoot a high-pressure stream of liquid resin at the attacking insect. This liquid is thoroughly repellent and poisonous, but for good measure the resins in the liquid can turn solid when exposed to air and seal a small insect in a tomb.
The squirt gun stores its chemicals in a network of canals in the leaf. When an insect bites a leaf canal, the liquid squirts out as far as 1.5 metres, drenching a small insect in deadly secretions. Larger insects that survive the attack suffer reduced growth and life expectancy.
This is an arms race between plant and insect that has been going on for millions of years, and in that time some species of beetle have figured out how to puncture the plant gun, by carefully nibbling a series of small notches in the leaf. Some beetles will spend up to an hour disarming the leaf before eating it, but even so the insects later suffer slow growth and an early death.
