Check the listing on page 445 in the Sunset Western Garden Book. Praying mantis egg cases are for sale in some nurseries. Mantids are voracious eaters but do not confine their appetites to predators. They will prey on beneficial insects as well so are not recommended for controlling garden pests. Frequent watering is often a factor in the decline of trees and shrubs.
Excess water prevents oxygen from reaching roots, a primary cause of root disease.
It may be too late for your cypress if it is suffering from phytophthora root rot. You may want to consult a certified arborist. You need to improve drainage and plant non-susceptible plants. 209-11 of Pests of Landscape Trees and Shrubs for additional information. Deep, infrequent watering is the general rule for tree irrigation.