There are around 2000 species of tiger beetles (Order: Coleoptera) worldwide and over 100 are found in North America. They live along sea and lake shores, on sand dunes, stream edges, clay banks, saline flats or woodland paths.
Tiger beetles are closely related to ground beetles. However, tiger beetles differ from ground beetles in that the head of a tiger beetle is wider than its thorax (located between the head and abdomen).
Although small in size, tiger beetles are important predators of the insect world and, unfortunately, a favorite among collectors. Fortunately, the scientific community finds tiger beetles excellent models to research ecology, biology, morphology, thermoregulation, predator-prey interactions, biogeography and physiology. Consequently, tiger beetles are one of the best studied non-pest insects and even have their own journal, “Cicindela”, which is dedicated to their biology.
The tiger beetles are among the most recognizable of beetles. Most species are daytime sun lovers, until approached. Then these active, alert little insects run swiftly over the ground or fly quickly away. Some species prefer dusk or are nocturnal, attracted to lights and others even give off an odor when handled.
Common species of tiger beetles seem almost camouflaged, blending in with their habitat. They are a grayish brown to black with white spots and markings on their broad, almost oblong wing covers (known as elytra which serves to protect the actual membranous wings beneath). Others show a variety in coloration and markings and can be brilliant green, violet, or orange and black or iridescent blue and bronze.
Adult tiger beetles are about ½ inch long. They have large bulging eyes, pointed mandibles and relatively long antennae. Tiger beetles have a narrow thorax, which differentiates them from ground beetles, in that the head is wider than the thorax. The tiger beetle utilizes its long spindly legs to hold its body well off the ground.
Repeated mating begins soon after adults emerge from their burrows (from June through August) and last the remainder of the tiger beetle's six-week life span. A female can lay up to 3-to-4 eggs per day with several males attempting to mate with her. To prevent this, males exhibit a behavior known as “mate-guarding” or “contact-guarding.” The male uses his large jaws, grabbing the female’s thorax, then rides on top of her, discouraging other suitors.
Females are extremely specific in choosing an egg-laying site, appearing to favor damp sand or soil. She excavates a small hole, deposits a single egg, then covers the hole with sand or soil to discourage predators. There are three larval stages (instars). Larval development is dependent on climate and food availability, and requires 2- 4 years for completion.
The larvae of tiger beetles hatch from eggs and dig burrows in the soil that they enlarge as they develop. Burrows may be over a foot deep in hard-packed sand or soil, accomplished by loosening the sand or soil with its mandibles and using its head and thorax like a shovel to carry the sand or soil. Tiger beetle larvae are unique in that they have hooks located on the back of their abdomen to anchor them to the side of the burrow. They rarely leave their burrow but wait at the burrow’s entrance to ambush small arthropods.
Generally speaking, tiger beetles larvae are large, flat-headed, hump-backed grubs with powerful, sickle-shaped jaws that flip backwards to capture prey that wanders by. The tiger beetle larva's main occupation is feeding. When seeing a victim, the larva attacks with lightning speed, pulling it down into the burrow and devouring it. Similar to a spider, larvae secrete digestive enzymes to help break down its food before ingestion.
Prior to pupation the larva plugs its burrow entrance with sand or soil and then forms a pupa cell within. The pupa does not feed during this transitional stage, which lasts three or more weeks. After emergence from the pupa, the new adult waits three days before digging itself out of the burrow, as its exoskeleton needs that time to harden. Once emerged from the burrow, the adult is still soft and light colored, making it an easy prey for plunders.
Among species of tiger beetles occurring in the Galveston-Houston region, Cicindela ocellata rectilateraes is one of the most commonly encountered. Cicindela ocellata rectilateraes (this species does not have a common name) is ferocious and stealthy predator, which is why they are called tiger beetles. They ambush and consume a wide variety of small of arthropods including ants, beetles, caterpillars, flies, grasshopper nymphs, insects, spiders and even small terrestrial crustaceans.
Another tiger beetle that gardeners may see is Megacephala carolina carolina. This species is similar to Cicindela ocellata rectilateraes in its hunting modes and as well as its preferred prey. However, Megacephala carolina carolina has a very impressive—and very powerful—pair of mandibles for catching and retaining its prey (see photo at left).
From its crouching perch, a tiger beetle waits for its prey. Their vision is acute and when a victim passes by, the tiger beetle lunges and grabs its target (like a tiger). The quarry is clenched between powerful sickle-like mandibles and devoured on the spot. The fast-moving adults will also run down their target. Some tiger beetles can run at a speed of 5 mph and have been considered the fastest running land animal for its size.
Tiger beetles are beneficial insect for a multiple of reasons. As previously stated, they feed on pests and in turn; spiders, robber flies, dragonflies and vertebrates including toads and lizards, prey upon tiger beetles.
Tiger beetles are studied as bio-indicators of environmental quality. They are dependant on the environment for their body temperature and seek microclimates for their burrows. Because of their restricted habitat requirements, the tiger beetle has disappeared from many beaches due to off-road vehicles and human trampling. As we take away more of their native environment, tiger beetles have fewer places to live and survive. Undisturbed sandy areas is crucial to tiger beetles.
Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.
All digital photographs are the property of the Galveston County Master Gardener Association, Inc. (GCMGA) 2002-2015 GCMGA - All Rights Reserved.