Tiger Beetle Morphology
The most important characters for identifying tiger beetle species are illustrated below. These feature are generally easy to recognize, and tiger beetle identification is not terribly difficult. Let's begin with the head. The first structures you'll probably notice on the head are the large, sickle-shaped mandibles. At the anterior (front) end of the head above the bases of the mandibles is the upper lip, or labrum. Depending on the species, the distal end of the labrum may possess either one or three small projections called "teeth." A labrum with one tooth is referred to as unidentate and a labrum with three teeth is referred to as tridentate. Immediately posterior to the labrum is a thin, strap-like sclerite called the clypeus. The suture between the labrum and the clypeus, the clypeolabral suture, is somewhat flexible and allows the labrum to move. Posterior to the clypeus is the front of the head, or frons. The suture between the clypeus and the frons is rigid and is called the frontoclypeal suture. On the frons just in front of each eye are the antennae. Each antenna has eleven segments. The first or basal most segement of the antenna is called the scape. At the distal end of the scape are the sensory setae which are arranged in a single transverse row. Below the sensory setae are the accessory setae which appear scattered over the scape. On the frons above each compound eye is the supraorbital region (think of it as the eyebrow). Below each eye on the sides of the head are the cheeks, or genae (singular = gena). Behind the head is the middle body region, or thorax. The thorax is divided into three parts: the front part is the prothorax, the middle part is the mesothorax, and the hindmost part is the metathorax. Each thoracic segment bears one pair of legs. The legs of tiger beetles are quite long and adapted for running. In top, or dorsal view, only the prothorax and a very small part of the mesothorax are visible. Sclerites of each thoracic segment are prefixed either pro-, meso-, or meta-, depending on the segment. The top sclerite of the prothorax is called the pronotum. The large sclerite on the side of the prothorax is called the proepisternum. The bottom or ventral sclerite surrounding the inner bases of the front legs is called the prosternum. If you look closely just behind the pronotum along the midline of the body you will see the small, triangular mesoscutellum, which is part of the mesothorax. Attached to mesothorax are the elytra (singular = elytron). The elytra are actually the modified forewings of beetles that enclose and protect the hindwings when not in use. Beetles belong in the order Coleoptera, which translates as "sheathed wings" (coleo = sheath, ptera = wings). The elytra are very important in tiger beetle identification. Many species have obvious markings called maculae or maculations on the elytra. If the elytra have no markings, they are said to be immaculate. The anterior most marking (on the "shoulder") is the humeral lunule. It is usually crescent shaped (hence the name "lunule" referring to a crescent moon). Along the lateral margin of each elytron is the marginal line. The middle band projects medially (towards the middle) from the median line. At the tip of each elytron is the apical lunule. Also, the tips of the elytra may bear very small saw-like teeth. Such elytra are said to be serrulate. The elytra may or may not have punctures. Elytra with punctures are called punctate, and those without punctures are impunctate. The dorsal surface of the abdomen is hidden beneath the elytra, but the ventral surface is visible and is usually iridescent blue or green.
Dorsal view of body Lateral view of head and prothorax
Dorsal view of head