Stag beetle

The stag beetle is a fascinating insect belonging to the family Lucanidae. This family contains approximately 1,200 different species divided into four subfamilies. While most species grow to a size of about 2.5 centimeters, some individuals can grow much larger. One of the most famous members is Lucanus cervus, found throughout much of Europe. This specific species is the largest terrestrial insect on the European continent.

Male stag beetles are famous for their massive mandibles, which are specialized mouthparts. These mandibles often resemble the antlers of a stag deer, which is how the insect got its name. Males use these tools to wrestle with one another. They fight to secure favored mating sites or to protect food sources like decaying fruit and tree sap. During these battles, a male's goal is to use his mandibles to dislodge the tarsal claws of his opponent. By grabbing these foot claws, the beetle can disrupt the other male's balance.

Female stag beetles look quite different from the males. They are usually smaller in size and possess much smaller mandibles. However, their mandibles are actually much more powerful than those of the males. You can also identify a female by looking at her back. During her larval stage, her cream-colored, fat ovaries are visible through her skin about two-thirds of the way down her back. Because their mandibles can exceed their own body size, adult stag beetles are often inefficient runners. They are typically very slow and often prefer to fly to new locations.

The life of a stag beetle begins as a larva, often called a grub. These larvae spend several years living inside rotting wood. They progress through three distinct larval stages before they are ready to change into adults. In the final stage, known as L3, the grubs of larger species can become quite massive. For example, a grub from the Prosopocoilus giraffa species may grow to be the size of a human finger. To complete their transformation, the larvae construct a pupal cell using particles of soil and pieces of surrounding wood.

Humans have had many different relationships with these beetles throughout history. The Roman writer Pliny the Elder recorded that a man named Nigidius called the beetle lucanus. This name came from Lucania, an Italian region where the insects were used as amulets. In England's New Forest, people once held a superstition that the beetles were "devil's imps." They believed these insects were sent to attack corn crops, which led people to stone them on sight. In modern times, the perception has changed, and people in South Korea and Japan often buy them as pets.

Scientists can trace the history of these beetles back millions of years through fossils. The oldest known fossil in this group is Juraesalus, which dates to the late Middle Jurassic period. This fossil was discovered in the Daohugou Beds of Inner Mongolia, China. While researchers once thought it belonged to the Aesalinae subfamily, they now view it as a basal member of the family. Another ancient group, the genus Litholamprima, is known from the Lower Cretaceous period in China's Yixian Formation.

There is also a complex biological relationship regarding the size of a beetle's mandibles. This is known as static allometry, which describes how the size of one body part varies in relation to the rest of the body. In Lucanid males, the size of the mandibles often varies among different individuals. This scaling relationship is influenced by both genetic factors and environmental conditions. Often, the size of these large mandibles is proportional to the length of the beetle's elytron, which are the hardened forewings that protect the insect's body.