Life cycle of the monarch – the caterpillar

A fifth instar caterpillar of the monarch butterfly eating a swan plant leaf, in close-up, with its mouth parts (mandibles), eyes (ocelli or stemmata), and tentacles (filaments) visible.

The newly hatched monarch caterpillar starts out tiny (2-3mm long), but, over the next nine to 20 days, it will grow to many times that size – up to about 45mm long. By weight, that is 7,000 times its size on hatching! To grow so much, it has to eat – and, as you’ll know […]