Praying Mantis; Tenodera aridifolia sinensis
These hungry beasts eat various mites, insect eggs, aphids, leafhoppers, mosquitoes, caterpillars and other insects when young. The adult mantis will eat larger pest insects, just about any of them.
When you first get the egg case of a preying mantis, you might recognize that you have seen them around. They are as wildly alien-looking as the mantis itself, but not uncommonly seen around Tucson.
Sometime after the last frost I usually pin a paper bag or pillow case somewhere in the garden away from the reach of ants (like on a stake or any structure above the ground) and set the egg case inside. I check them twice a day and look for signs of hatching. Once they hatch, be ready. You will want to spread them out as far as possible. These little guys are so tough, they will start eating each other. Obviously the more that survive, the more you can control the unwanted insects in the garden.
The best thing you can do for them after they have hatched is ensure that there are lots of plants for them to hang out in. They will likely stay in the garden rather than go to a place that lacks the shelter of plants. Those individuals that survive will breed and in fall the female will lay eggs just before she succumbs to frost.
I hire my assassins from Arbico. They should be available sometime in January of each year.