They do eat insects, but they aren t picky. They ll eat anything in their path, including each other. If you find some naturally occurring in your yard, enjoy them, but don t buy them to save your plants from insects. Something newer as a source of beneficial insects are beneficial nematodes. Data is somewhat iffy as to effectiveness.
Timing can be very important.
They also won t tolerate dry soils. But they are an option for soil born insects. Problems Controlling insect pests can be a problem, whether it is in your lawn or flowers, fruits or vegetables. Monitor frequently for problems and control them as soon as they are spotted. But, also, practice sound gardening practices.