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Friday, April 6, 2018

Blazing Beetles

Big Sand Tiger Beetle, Cicindela formosa
Over 2500 species and subspecies of tiger beetles are currently described worldwide, with more than 45 species occurring in Texas.  Tiger beetles get their name from their cat-like predatory behavior, performing an unusual form of pursuit where they alternatively sprint quickly toward their prey then stop and visually reorient, eventually running down their target.  In fact, some tiger beetles can run at a blazing speed of 5 mph, and are considered one of the fastest running land animals for their size!

Tiger beetles are believed to be closely related to ground beetles, but they differ in terms of their proportions.  Tiger beetles are about one inch long on average, with a head wider than its thorax, which is located between the head and the abdomen.  They also have large bulging eyes, long spindly legs, and oversized sickle-shaped mandibles to grab prey and devour it on the spot.  Tiger beetles are important predators in the insect world, feeding on a wide variety of ants, beetles, grasshopper nymphs, flies, and spiders.  They are most often found in sandy areas, stream edges, clay banks, and woodland paths.  Many are active in the daytime, and the colors and patterns on their oblong elytra (or wing covers) are often iridescent and striking. 

Festive Tiger Beetle, Cicindela scuterllaris
Some of the more common tiger beetles in our area include members of the Cicindela genus, which comes from the Latin and means ‘glowworm’, referring to the fact that most of these species have metallic, flashy elytra.  In Eastern and Central Texas, the Big Sand Tiger Beetle (Cicindela formosa) and Festive Tiger Beetle (Cicindela scutellaris) prefer the dry sandy areas of post oak woodlands.  The Big Sand Tiger Beetle has luminous reddish-purple elytra with irregular white marks around the edges and the Festive Tiger Beetle’s elytra are iridescent reddish-bronze to purple to blue-green or blue-black with reduced or absent spotting.  Both species can be sighted late spring into fall.

Ocellated Tiger Beetle,Cicindela ocellata 
Abundant along water edges, the Ocellated Tiger Beetle (Cicindela ocellata) is most active in the summer, and can be identified by its bronze elytra speckled with 8 cream-colored spots (4 on each elytra).  Ocellated means having one or more ocelli, or eye-like markings. The Six-spotted Tiger Beetle (Cicindela sexguttata) is the probably the most commonly observed species on dirt paths in grassy areas seldom far from woods, and has brilliant green elytra with typically six tiny white spots on the lower half (3 on each elytra). 

Six-spotted Tiger Beetle, Cicindela sexguttata
Tiger beetles are also excellent indicators of environmental quality and are often studied as bioindicators.  Many require undisturbed sandy areas and specific microclimates for their burrows. With rapid urbanization and human disturbance of natural areas, these blazing beetles have fewer places to live and survive.  They are very sensitive to changes in the environment, and are among the first species to react to pesticides, misuse of natural habitat, and climate change.