The white beach tiger beetle (Cicindela dorsalis) can be found in the eastern and southern coastal regions of the United States, stretching from Massachusetts to Florida, and along the Gulf of Mexico from Florida to Texas. It is common to find them in light, sandy areas such as dry riverbeds.
Biogeographic Regions: nearctic (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Adult Cicindela dorsalis can reach 13-15 millimeters in length and can be identified by their long legs, large prominent compound eyes, and eleven-segmented, filiform antennae. Adults also possess bright orange-red hues on the anterior side of their bodies, metallic green legs, and predominantly white wings. Larvae are S-shaped, and have hooks along their abdomen to help keep them in place within their vertical burrow.
Range length: 13 to 15 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
As the common name implies, the white beach tiger beetle can be found in coastal areas with white sandy beaches. Cicindela dorsalis prefers a moderate climate with average temperatures above 15 degrees Celsius. These beetles also prefer a habitat with moderate to arid rainfall totals.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; chaparral
Aquatic Biomes: coastal
Comments: All subspecies occur only on seashores, including beaches of lower Chesapeake Bay.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Larvae wait in their burrows to ambush passing prey; their wide head helping to disguise the opening of their burrow. They will usually eat their prey at the bottom of the burrow unless it is too large to fit down the hole. A first instar larva needs at least one meal in order to molt into its second instar. Because instars two and three of require several meals during their development, serious competition for food develops between individuals whose burrows are close to one another. The larvae have adapted to this by having a long developmental period and an ability to feed over a twenty-four hour time period.
Animal Foods: insects
Primary Diet: carnivore (Insectivore )
Cicindela dorsalis larvae are commonly parasitized by members of Bombyliidae, and Tiphiidae. Adults are preyed upon by amphibians, reptiles, various insectivorous mammals, and many types of birds.
Life History and Behavior
This species detects is surroundings visually, and through ground vibrations.
Communication Channels: visual
Other Communication Modes: vibrations
Perception Channels: visual ; vibrations
Female tiger beetles lay eggs individually into small depressions that are later enlarged into burrows by the larvae as they mature, passing through three larval stages, or instars. The pupal stage occurs following the third instar. The larvae are responsible for digging a pupal chamber adjacent to the burrow. The larva will lie on its back and gradually lose mobility in its appendages; eventually its exoskeleton will become a translucent and creamy-white pupa. The pupal stage usually lasts 18-24 days, during which time the pupa becomes darker. The adult Cicindela dorsalis emerges through a slight hole in the dorsal portion of the pupal case, a process which requires two hours to complete.
Development - Life Cycle: metamorphosis
Mating occurs on warm, humid days. Female tiger beetles lay eggs individually into small depressions that will later be enlarged into burrows by the larvae as it matures. Tiger beetles are only known to produce one generation per year.
Female tiger beetles have sensitive hairs on their abdomens that detect moisture content in the soil. Appropriate soil conditions are essential to larval survival and development, so these hairs play a major role in the females selection of where to oviposit her eggs.
Key Reproductive Features: semelparous ; sexual ; fertilization (Internal ); oviparous
After oviposition, there is no further known parental investment.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female)
Populations of C. dorsalis are in no danger and have no special status.
US Federal List: no special status
CITES: no special status
National NatureServe Conservation Status
Rounded National Status Rank: N3 - Vulnerable
NatureServe Conservation Status
Rounded Global Status Rank: G3 - Vulnerable
Reasons: This species had been ranked G4 for about 20 years, and that may be correct. However, none of the subspecies are ranked T4, although two are ranked T3T4, and one is federally listed and C. media at least has also declined substantially in range extent. The Florida subspecies is actually documented from few places. The species as a whole is not imminently imperiled, but there is insufficient post-2000 (and post Hurricanes Rita and Katrina) information to justify continuation of the old G4 rank.
Relevance to Humans and Ecosystems
Cicindela dorsalis have no negative affect on humans unless they are mishandled, in which case they tend to bite.
Negative Impacts: injures humans (bites or stings)
Cicindela dorsalis is considered a beneficial insect, in both larval and adult stages, because they prey on other insects, such as many species of leaf beetles that destroy crop plants.
Positive Impacts: controls pest population
Cicindela dorsalis (common name eastern beach tiger beetle) is a species of tiger beetle.
The body length is 13 to 15 millimetres (0.51 to 0.59 in). The head and thorax are bronze-green, the legs are long and slender, and the elytra are white to light tan with narrow bronze markings. The head has long antennae, large compound eyes, and powerful jaws. There are white hairs on the pronotum and the sides of the abdomen. The pale coloration provides camouflage for the beetle on the light sand. The larvae are grub-like, with long, segmented bodies and large jaws similar to those of adults.
The larva of the subspecies C. d. media is notable for its ability to leap into the air, loop its body into a rotating wheel and roll along the sand at a high speed using wind to propel itself. If the wind is strong enough, the larva can cover up to 60 metres (200 ft) in this manner. This remarkable ability may have evolved to help the larva escape predators such as the tiphiid wasp Methocha. Wheel locomotion in nature is extremely rare and has only been observed in a few animals around the world.
Range and habitat
Four subspecies of C. dorsalis are known. C. d. media is found along the southeast coast of the United States, including South Carolina. C. d. dorsalis is found along the northeast coast. C. d. saulcyi and C. d. venusta occur along the coasts of Florida, the Gulf of Mexico, and Mexico. In general, C. dorsalis is most abundant on broad, fine-sand beaches that are highly exposed to tidal action and relatively undisturbed by humans. In order for the beetles to breed, beaches need to be at least 100 metres (330 ft) long and 2 metres (6 ft 7 in) wide, 5-8 being the optimal width. The eastern beach tiger beetle prefers a climate with average temperatures exceeding 15 °C and moderate to arid rainfall totals.
The entire life cycle lasts 2 years. Adults emerge between mid-June and mid-August, usually reaching peak abundance by mid-July and declining by September. They spend the day foraging in the intertidal zone when the weather is warm and sunny. They feed on small invertebrates including flies, ants, and amphipods, but will also scavenge dead fish and crabs.
Mating takes place between mid-July and early August when the weather is warm and humid. Females lay their eggs in the intertidal zone. They use sensitive hairs on their abdomen to determine whether the soil moisture content is suitable for larval survival and development. Oviposition takes place at night. The female uses her ovipositor to create a small hole in the sand where she deposits the eggs individually.
Eggs hatch in mid-August, and the larvae dig vertical burrows where they secure themselves using hooks along their abdomen. They are predatory and prey on passing insects and other small invertebrates. Tiger beetle larvae go through three instars before pupating. They usually reach the second instar by September. As winter approaches, the larvae dig new burrows higher up the beach to protect themselves against storms and wave activity. After overwintering, they emerge in late May and June. Then they reach the third instar and overwinter again. The following spring they pupate in their burrows and emerge as adults.
The subspecies C. d. dorsalis (northeastern beach tiger beetle) suffered a major decline over the last 20 years. It used to be found all along the Atlantic coast of the USA from Massachusetts to Virginia. Today it only occurs in the Chesapeake Bay of Maryland, Martha's Vineyard island off the coast of Massachusetts, and Virginia. This decline was caused by the destruction and disturbance of the beetle’s natural beach habitat by human activity, one of the greatest threats being shoreline hardening by the placement of rip-rap. Other threats include pollution and pesticides, as well as the use of off-road vehicles that crush adults and larvae, also damaging larval burrows. In 2009 the United States Fish and Wildlife Service recommended C. d. dorsalis be uplisted to endangered status.
- Natural Heritage Endangered Species Program: Northeastern Beach Tiger Beetle
- "White Beach Tiger Beetle" (PDF). DNR. Retrieved March 22, 2013.
- Wind-Powered Wheel Locomotion, Initiated by Leaping Somersaults, in Larvae of the Southeastern Beach Tiger Beetle (Cicindela dorsalis media)
- USFWS. Cicindela dorsalis dorsalis Five-year Review.
- Animal Diversity Web. Cicindela dorsalis (northeastern beach tiger beetle)
- The State Of New Jersey. Northeastern Beach Tiger Beetle, Cicindela d. dorsalis
- Observations of Oviposition Behavior Among North American Tiger Beetle (Coleoptera: Carabidae: Cicindelinae) Species and Notes on Mass Rearing
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