Unaware of danger, a small animal sips from the water's edge on a scorching summer day. Suddenly a tiger bursts from its lair. Its powerful jaws with jagged teeth clamp down tightly on the animal, bringing a quick death. It's a scene that has played out countless times around the watering holes of Missouri.
Ferocious tigers in Missouri? The thought of it is enough to give you goose bumps. Missouri's tigers, however are not large felines but small beetles. Tiger beetles may not be imposing to us, but to a shore fly, these marauders of the insect world are every bit as scary as a Bengal tiger.
Tiger beetles encompass a distinctive and fascinating group of Missouri insects. Nationwide, there are 147 species of tiger beetles, 21 of which live in Missouri. Many species have striking metallic colors and markings. Observers see them most frequently in sandy, disturbed habitats like sandbars or erosion cuts, but they also live along muddy banks, on glades and in forest litter. Some species are common and widespread throughout Missouri, while others are rare and localized. Tiger beetles usually group in open habitats with little vegetation, making it easy to observe their behavior.
Their combination of beauty, variety and high visibility makes tiger beetles a popular group to study. Only butterflies, dragonflies and a few of the larger groups of beetles, such as scarab beetles and wood-boring beetles, rival their popularity. Tiger beetles often run fast and fly strong, which makes them challenging to collect or photograph. Because tiger beetles are often restricted to specific natural communities, they make excellent subjects for ecological studies. Learning about them also is an enjoyable way to spend time outdoors.
Tiger beetles are members of the vast insect order Coleoptera, which is the largest order in the animal kingdom. At least 40 percent of all described animal species are beetles, and most of the remainder are other types of insects.
Tiger beetles belong to the family Cicindelidae and are closely related to the ground beetles, which belong to the Carabidae family. The tiger beetles' distinguishing characteristics include a cylindrical body; long, thin legs; prominent head with large, bulging eyes; and large, sickle-shaped jaws with sharp teeth. Some ground beetles look similar to tiger beetles, but tiger beetles are distinguished by the location of the antennae-toward the front of the head below the inside margins of the eyes. The antennae of ground beetles are below the eyes just above the mandibles.
Like all other beetles, tiger beetles have four life stages: egg, larva, pupa and adult. Eggs are laid in the soil and are rarely seen. The larva is like a caterpillar with a large, flattened head, two sickle-shaped jaws and a hooked hump on its back.
The larva digs a burrow in the soil and waits at the opening for prey to come close. Its flat head is camouflaged to match the surroundings and lies flush with the surface. When prey is within range, the larva springs out of its burrow, seizes the prey with its jaws and drags it back into the burrow. The hooked hump prevents the struggling prey from pulling the tiger beetle larva completely out of its burrow.
The larva spends its entire life in the burrow, molting periodically and enlarging the burrow as it grows. When fully developed, the larva closes the burrow, transforms into a pupa and emerges from the burrow as an adult beetle.
Tiger beetles may be active either during spring and fall or during summer. Adults of spring-fall species emerge from larval burrows in late summer or early fall as sexually immature individuals. They remain active for up to several weeks and then burrow back into the ground during the winter. In the spring, they re-emerge sexually mature. They mate and lay eggs, and then die during summer. Eggs hatch during summer, and larvae complete their development the following summer.
Adults of summer species emerge as sexually mature individuals in early summer. They mate and lay eggs, and then die by the end of summer. Eggs hatch in summer, and larvae complete their development the following spring. Some species may require an additional year or two to develop, especially in northern climates.
Compared to most other groups of insects, tiger beetles are relatively easy to identify in the field. In most cases, each species of tiger beetle in Missouri has a unique pattern of white markings on its wing covers. This pattern, along with body color, is used to identify species.
Tiger beetles are often quite wary, so one must approach them very slowly to observe them.
Although some species live in a variety of habitats, others have specific preferences regarding soil type, moisture, salinity, slope, sunlight and vegetation. Knowing the habitat preferences for individual species also aids in identifying them.
Some of Missouri's tiger beetles live in riparian habitats, especially on sandbars along large rivers. The common shore tiger beetle (Cicindela repanda) is the most common species encountered on sandbars. However, one also may find hairy-necked tiger beetles (C. hirticollis) and, possibly, coppery tiger beetles (C. cuprascens). These species are brown like the sand of their habitat, making them difficult to see until they move. Another riparian species, the twelve-spotted tiger beetle (C. duodecimguttata), prefers muddy stream banks and pond margins. Its color is much darker than the sandbar species.
Several other Missouri tiger beetles prefer dry soils in upland habitats. Road and erosion cuts in clay soils are especially attractive to them. These soils tend to be red and sparsely populated with small green plants. Therefore, it's not surprising that the species encountered in this habitat, such as clay bank tiger beetles (C. limbalis), cow path tiger beetles (C. purpurea) and splendid tiger beetles (C. splendida) tend to be largely red and green in color. Adults often colonize steep banks.
Several other upland species prefer dry sand habitats, such as old road cuts through sand soils, dry sand pits and clearings in pine-oak forest with sandy soils. The big sand tiger beetle (C. formosa) is a handsome species found throughout the state in such habitats. Smooth tiger beetles (C. scutellaris) also prefer these habitats but appear to be restricted to the southeastern part of the state.
A few Missouri tiger beetles live in relatively dense woodlands. They include the six-spotted tiger beetle (C. sexguttata), which is perhaps the most commonly encountered tiger beetle in the state. It has a brilliant, metallic green color and congregates in sunny forest openings. Woodland hikers often see these beetles during spring, but usually not until they take flight.
The saline spring tiger beetle (C. circumpicta johnsonii), has the most specific habitat requirements. It is restricted to saline soils around natural salt springs in central Missouri. Adults are bright violet-blue with white markings, making them quite visible. These saline communities are extremely rare in Missouri. Protecting them will help ensure the survival of this vivid tiger beetle species, as well as other unusual plants and animals.
Some tiger beetle species are generalists, which means they live in many different habitats. For example, punctured tiger beetles (C. punctulata) live in disturbed land, trails, road cuts, sand pits, agricultural fields and even city lawns. Red-bellied tiger beetles (C. rufiventris) live on gravel, rock outcroppings and coarse sand. Oblique-lined tiger beetles (C. tranquebarica) prefer sandy areas, alkaline or saline flats, creek banks and trails.
Threats to tiger beetles
Tiger beetles require suitable habitat, so human activities can have a significant impact on their distribution and abundance. Dredging and straightening natural water courses threaten species that prefer the water's edge, while fire suppression endangers those that need dry, open habitats.
Conversely, road, borrow sand pit and pond construction have increased habitat for some tiger beetle species. Insect collecting is sometimes cited as a threat to rare species, but this has been documented as a direct factor in only a few cases in which the species has a highly specific preference for limited habitat, does not disperse well and is easy to capture.
To collect insects of any kind in Missouri, one must possess a wildlife collector's permit. Additional permits may be required on certain public lands. Applications for wildlife collector's permits are available from the Missouri Department of Conservation.
Tiger beetle conservation is important, and amateur naturalists can help the effort by contributing valuable information. Several organizations in Missouri currently monitor local butterfly populations through annual counts, and the same could be done with tiger beetles. In fact, tiger beetles are easier to identify in the field than many butterflies, making them especially suitable for conservation study.
Photographing or collecting specimens increases our knowledge about their distribution in the state, and noting the presence of larvae identifies whether or not populations are successfully breeding. Such observations will be more valuable if locality, date, habitat and other information is document.
If you would like to help with tiger beetle conservation in Missouri, contact the Missouri departments of Conservation or Natural Resources, The Nature Conservancy, the Audubon Society, or Webster Groves Nature Study Society office for ideas.
For more information about tiger beetles visit <http://ianrwww.unl.edu/ianr/ entomol/nebraska_tigers/tigers_home.htm> on the Internet.