A strange kind of baby rattle? A musical instrument from a foreign land? No, these Styrofoam-like masses are praying mantid egg cases! This is how praying mantids spend the winter. As temperatures rise in the spring, hundreds of miniature praying mantids will emerge from these egg cases and immediately begin their search for other insects to eat. Praying mantids have such a voracious appetite for insects that some garden supply companies sell these egg cases to help control plant-eating insects in the garden. See if you can find a praying mantid egg case around your house or yard this winter.