Simplify the following text for a Grade 6 native English-speaking person.
Original: It is the only caterpillar to feed on plants in the family Zygophyllaceae . Apparently they feed exclusively on the leaves of three Guaiacum species : G. sanctum and G. angustifolium in Central and North America and G. officinale in South America and the Caribbean .
Simplified: It is the only caterpillar to feed on Guaiacum sanctum .