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NATURAL HISTORY

ANDREW’S DUNE SCARAB BEETLE } Pseudocotalpa andrewsi
FAMILY: Scarabaeidae

DESCRIPTION: Andrew’s dune scarab beetles are a golden-brown color, covered with long, pale, fine hairs and ranging in length from 13 to 18 millimeters. These beetles have well-developed flight wings and can be differentiated from other closely related scarab beetles by their smaller size and the deep concave shape of their clypeus (a shieldlike plate on the front of the head). Antennae have distinctive terminal clubs composed of leaf-like plates that can be opened and closed.

HABITAT: The beetles require areas of fine sand and creosote bush scrub as well as areas of active and partially stabilized dunes with widely scattered perennial vegetation cover. In particular, they prefer low dunes on the margin of dense patches of scrub vegetation that form finger-like extensions into the dunes.

RANGE: The Andrew’s dune scarab beetle is restricted to the Algodones Dunes of Imperial County in southeastern California and northern Baja California, Mexico.

MIGRATION: The Andrew’s dune scarab beetle does not migrate.

BREEDING: Breeding takes place between February and May. Immediately after twilight, male and female beetles emerge from the Dunes and fly for a few minutes in aggregations around nearby shrubs such as creosote, California buckwheat, palo verde, and desert needle. After swarming, a female will alight on open sand; several males will converge upon her and attempt to mate.

LIFE CYCLE: Beetles undergo complete metamorphosis from larvae to adult. During the day, they remain buried at the interface between wet and dry sand, at depths varying from five to 30 centimeters. They emerge at twilight, experience a brief period of activity, and then rapidly disappear, with the exception of a few stragglers. The Andrew’s dune scarab beetle is active on the dune surface for only 10 to 30 minutes an evening for three to four months, in breeding clusters only two to three meters wide. For the rest of the year, it lives buried in the sand.

FEEDING: The creosote bush is believed to be a likely host plant for the species.

THREATS: Due to the beetle’s highly restricted geographic range and specialized habitat needs, it is particularly vulnerable to disturbance from heavy off-road vehicle use of the Algodones Dunes.

POPULATION TREND: The population of Andrew’s dune scarab beetles on the Algodones Dunes is believed to be declining.

Photo © Andrew Harvey