Assassin Bug
Zelus
This predator is hunting upon the flower head of a Desert Marigold. In this case it is harming slightly the plant by detering pollinators.
Reduviidae -- Assassin Bug Family
Assassin bugs of many kinds are found in the Sonoran Desert and are generalized predators taking caterpillars and other mostly slow moving prey. Gardeners should encourage these insects by eliminating chemical pesticides and leaving some weedy vegetation in border areas.
This common species uses an interesting technique for capturing prey: the tibiae on the first pair of legs are coated with sticky glue which helps hold prey while the sharp beak penetrates and delivers salivary poison. If handle carelessly, reduviid bugs can deliver a sometimes painful bite.