Sanjida O'Connell meets Dave Wood who shows her white poplar trees with puss moth caterpillars on them. They are large for caterpillars. Agitated at the attention, a caterpillar squirts poo and red filaments from its backside. This is a method of scaring off predators. The caterpillar also rears up - and if really angry it will squirt acid. When it is ready to pupate the caterpillar changes to a brown colour and finds a shelter to spin its cocoon. Sanjida follows a caterpillar across the grass to where it is digging down into the ground by a stump. It needs to get well down into the ground to avoid the cold, as it will not hatch from its pupa until next spring.