Dr. Buss with the University of Florida Insect Identification Laboratory in Gainesville believes this is the yellow-banded millipede. Like other types of millipedes, the yellow-banded millipede feeds on decaying plant material and other organic matter and would not be responsible for damage to your cardboard palms.

A more likely scenario is that the plant developed a root rot disease and the millipedes are feeding on the decaying root tissue. Cardboard palms are quite drought tolerant once established and require little if any supplemental irrigation. This is especially true during the winter months.

More information on the yellow-banded millipede can be found here:
http://ipm.ifas.ufl.edu/pdf/Yellow-banded%20millipede.pub%20(Read-Only).pdf