Answer: In order for the predatory insects to be helpful, there needs to be a supply of the pest available for them to eat. In many cases, they will arrive in response to a high pest population and take care of it naturally. This is a natural balance especially possible in a yard like yours where there is no chemical use serving as a barrier to them or killing them off when they do arrive. In other words, if the caterpillars are not at your house, releasing the beneficials is not really necessary -- they will leave in search of food! In your yard it is possible that the birds will take of any caterpillars that arrive, or at least control the population to a tolerable level. Also, the caterpillars will not come unless you have a suitable food source ie the specific plants they eat for them. They may in fact be baby butterflies, so any plant damage might be tolerable due to that fact. Finally, if you need to control the caterpillars, you (and your neighbor) might look into using Bt as this only affects caterpillars. FOr information about bats, how to install a bat house, and how to provide good habitat for bats, you might wish to contact Bat Conservation International
for more information. I hope this answers your question.
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