You can destroy 1 "Desert Protector" to save multiple Insects that would be destroyed at the same time, such as with "Nobleman-Eater Bug".
You can only use 1 "Desert Protector" at a time; if 1 or more Insects are about to be destroyed, you can only destroy 1 "Desert Protector".
If "Desert Protector" and your Insect(s) would be destroyed at the same time, you cannot use "Desert Protector" to save the Insect(s).