I found this worm with rice all over it on my tomatoes this morning. It’s a fascinating lesson in nature – a tomato worm with a parasite: wasp eggs.
The white rice structures are the pupating eggs of the Cotesia congregatus wasp, of the Braconidae wasp family. These wasps are deadly to a wide variety of garden pests like hornworms, caterpillars, beetles, squash bugs, and stink bugs. They generally will not sting a human unless handled.
The female wasp lays eggs just under the skin of the tomato worm. As the eggs hatch, they eat the worm alive.
In general you should kill any tomato hornworms you see. But, when they are covered with eggs like this guy, let them live, as they will provide food for very beneficial wasps!