Creosote Litter Leaf Beetle
Pachybrachis mellitus
In reality this beetle does not have an official common name. Finding one of these minute beetles requires a lot of uncommon searching ... many days and bushes might be searched without finding a one. This adult pair (male at left) was found on fresh growth of Creosote Bush (Larrea tridentata) near Bulldog Canyon in the Goldfield Mountains, Maricopa Co., Arizona on 11 Oct. 2008.
Chrysomelidae -- Leaf Beetle Family
Like all holometabolous insects, this leaf beetle leads a double life. When it first hatches from the egg it is a worm-like grub. It lives within a case constructed from fecal material and lives on the ground within the leaf litter. There it feeds on dead leaves and such - presumably dead creosote bush leaves. Eventually the mature grub forms a pupa which later ecloses into an adult beetle. The adult beetles are less than 4 mm long and are well camouflaged - they are present in spring and autumn when there is fresh growth.