The pictured rove beetle (''Thinopinus pictus'') is a wingless

rove beetle The rove beetles are a family (biology), family (Staphylinidae) of beetles, primarily distinguished by their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed. With over 66,000 species in thousand ...

which lives on the sandy beaches of the

West Coast of the United States The West Coast of the United States, also known as the Pacific Coast and the Western Seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the Contiguous United States, contig ...

from southern

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

. It is

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

, emerging at night from temporary sand burrows to feed on beach hoppers ('' Orchestoidea'').

Identification

Like other

s, ''T. pictus'' has shortened

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

, so that most of its

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

is exposed. Males average , females average . Males possess a cleft in the last abdominal

sternite The sternum (: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the su ...

, which makes them readily discernible from females. Their cryptic coloration varies geographically in response to lighter colored sand in the southern part of their range. Populations north of central

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

tend to be darker in response to the dark volcanic sand, while those in the southern range are quite pale. Because of this variation, ''T. pictus'' was once thought to be made up of two

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

Ecology

''T. pictus'' inhabits the sandy

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

; during the day, they hide in temporary sand burrows or under kelp and beach debris with a preference to inhabit the wettest and softest sand available. At night they emerge and move to the high tide level to find prey. Individuals switch between inactive ambush predation and active foraging for their prey, which consists mostly of beach hoppers (

Amphipoda Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

). They have also been observed eating beach flies,

isopods Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...

, and other ''T. pictus''. Males seem to feed less than females, but are more active than females, possibly to increase the chance of finding a mate.

Reproduction

The breeding season is thought to be from August to October. Dissected females have been shown to carry only 2–3 eggs, which are oviposited singly in the sand. These beetles likely have long lifespans in order to reproduce sufficiently. In the laboratory, eggs hatch at about 14 days.

Larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e are whitish with black markings. The duration of their instars is unknown.

References

External links

*http://bugguide.net/node/view/321754 * {{Taxonbar, from=Q7191211 Staphylininae Beetles described in 1852 Beetles of North America Wingless beetles Taxa named by John Lawrence LeConte