Pictured rove beetle
Encyclopedia
The pictured rove beetle (Thinopinus pictus) is a wingless rove beetle
which lives on the sandy beaches of the West Coast of the United States
from southern Alaska
to Baja California
. They are nocturnal, and emerge at night from temporary sand burrows to feed on beach hoppers (Orchestoidea).
s, T. pictus has shortened elytra
, so that most of its abdomen
is exposed. Males average 17 millimetre (0.669291338582677 in), females average 18 mm (0.708661417322835 in). Males possess a cleft in the last abdominal sternite, 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
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
.
; during the day, they hide in temporary sand burrows or under kelp and beach debris. A laboratory study and personal observations have indicated 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
). They have also been observed eating beach flies, isopods
, 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.
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
e are whitish with black markings. The duration of their instars is unknown.
Rove beetle
The rove beetles are a large family of beetles, primarily distinguished by their short elytra that leave more than half of their abdomens exposed. With over 46,000 species in thousands of genera, the group is the second largest family of beetles after the Curculionidae...
which lives on the sandy beaches of the West Coast of the United States
West Coast of the United States
West Coast or Pacific Coast are terms for the westernmost coastal states of the United States. The term most often refers to the states of California, Oregon, and Washington. Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean but can't be included in...
from southern Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
to Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
. They are nocturnal, and emerge at night from temporary sand burrows to feed on beach hoppers (Orchestoidea).
Identification
Like other rove beetleRove beetle
The rove beetles are a large family of beetles, primarily distinguished by their short elytra that leave more than half of their abdomens exposed. With over 46,000 species in thousands of genera, the group is the second largest family of beetles after the Curculionidae...
s, T. pictus has shortened elytra
Elytron
An elytron is a modified, hardened forewing of certain insect orders, notably beetles and a few of the true bugs ; in most true bugs, the forewings are instead called hemelytra, as only the basal half is thickened while the apex is membranous...
, so that most of its abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
is exposed. Males average 17 millimetre (0.669291338582677 in), females average 18 mm (0.708661417322835 in). Males possess a cleft in the last abdominal sternite, 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
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
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
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
.
Ecology
T. pictus inhabits the sandy intertidal zoneIntertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
; during the day, they hide in temporary sand burrows or under kelp and beach debris. A laboratory study and personal observations have indicated 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
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified...
). They have also been observed eating beach flies, isopods
Isopoda
Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...
, 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 ovipositedOviposition
Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....
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
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e are whitish with black markings. The duration of their instars is unknown.