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Northeastern Beach Tiger Beetle

Description

A large, attractive cream-colored beetle, the northeastern beach tiger beetle roams beaches along the Chesapeake Bay and parts of the Atlantic Coast. Adult beetles have green-bronze heads and thorax and paired dark markings on their cream-colored forewings (elytra). These predatory beetles sport large pinching jaws, long legs for fast movement, and long antennae. They are about 2/3 of an inch long while their larvae grow up to 5/8 inch and also have large jaws.

Habitat

Broad sandy beaches along the Chesapeake Bay and Atlantic Ocean provide the best habitat for these beetles. Adults live in the area between the high tide line and sand dunes, while the larvae live in burrows in the upper intertidal zone of the beach. Larvae require beaches that are at least 5 yards wide with some sand above the high tide mark. Because they live on beaches that are frequently unstable due to storm erosion and other disturbances, northeastern beach tiger beetles have adapted to their impermanent habitat. Some of the newly emerged adults will fly more than a mile to colonize new beaches. Their presence is an indicator of a healthy beach.

Food Requirements and Behavior

Adult beetles roam and fly over the sand in search of other insects and small crustaceans, grabbing them in their large jaws. They also scavenge dead fish and crabs for food. Adults are active day and night in warm weather, feeding, mating and laying eggs, peaking in numbers in July.

Larvae dig vertical burrows between 4 and 14 inches deep, depending on the size of the larva. They wait at the mouths of their burrows to catch small insects and crustaceans that pass by. Because they live in the intertidal zone where prey is most plentiful, their burrows are periodically covered at high tide. As the water rises they plug the burrows with sand, opening them again when the water recedes. If conditions are poor, a larva will crawl out of its burrow and relocate to a new site.

Life Cycle and Reproduction

In Virginia the adult beetles emerge from their cocoons in larval burrows in mid-June. Some fly off and relocate to more distant beaches while others remain on the beach on which they were born. After mating sometime between late June and August, females lay their eggs in the beach sand, often in shallow burrows they have dug. The larvae hatch approximately twelve days later and go through three instars or stages of development as they increase in size. It generally takes two years for larvae to become adults. They spend the winter months between November and March in hibernation in their beach burrows. In late spring third instar larvae envelop themselves in a cocoon in their burrows and emerge as adults in June.

Virginia Distribution

In the past northeastern beach tiger beetles could be found from coastal Massachusetts to New Jersey and on beaches of the Chesapeake Bay. However, the only two Atlantic coast beaches where native populations have survived are on Martha’s Vineyard. Beaches with significant numbers of the beetles are more abundant along the Chesapeake Bay. Sites where beetles are found can vary from year to year due to elimination of populations of larvae after storms and other beach disturbances and because some adults fly to new locations.

Status/Conservation Need in Virginia

Although the beach tiger beetle as a species is rated as common and globally secure, the northeastern subspecies is ranked very rare and imperiled both globally and by the Commonwealth of Virginia Department of Conservation and Recreation. The federal and state status of the northeastern beach tiger beetle is listed threatened and likely to become endangered in the future. Storms and beach erosion can eliminate local populations, but the greatest threat is from human use, particularly vehicle traffic on beaches that kills larvae in their burrows. Heavy foot traffic is also detrimental to larvae. Development on the shore along beaches negatively impacts habitat for the beetle.

The U.S. Fish and Wildlife Service has developed a conservation and recovery plan for sites inhabited by the beetle. Key components of the plan include monitoring of populations, protection of beach habitat from foot and vehicular traffic, and education of landowners and the public about the endangered beetle. The plan also calls for a reintroduction of the northeastern beach tiger beetle to suitable protected beach habitat.

Similar Species

The northeastern beach tiger beetle is one of four subspecies of beach tiger beetles (Cicindela dorsalis) inhabiting the coastal beaches of the Eastern U.S. and Gulf Coasts. Except for being slightly smaller and darker in color, Cicindela dorsalis media (no common name), a closely related subspecies, is very similar in appearance. It is found only on the Atlantic Coast beaches from southern New Jersey to Florida. Two other subspecies live on U.S. coastal beaches along the Gulf of Mexico.