The superfamily Cicadoidea encompasses a group of insects recognized as cicadas. These creatures are prominent across temperate to tropical regions globally, frequently marking warmer months with their characteristic acoustic displays. They represent a well-known component of various ecosystems, from deserts and grasslands to forests.
Classification and Physical Traits
Cicadas are classified within the order Hemiptera, distinguishing them as “true bugs.” As true bugs, they possess specialized piercing-sucking mouthparts for feeding on plant fluids. Their physical structure includes a stout body, large compound eyes on the sides of their head, and short antennae.
They have two pairs of membranous wings. The forewings are longer and often transparent, covering the shorter hindwings when at rest. A network of sturdy veins strengthens these wings, which can have an average span between 1 and 6 inches, depending on the species. The superfamily Cicadoidea is primarily divided into two families: Cicadidae, with over 3,000 described species, representing the vast majority worldwide, and Tettigarctidae, a much smaller family with only two rare, non-singing species found in Australia.
The Cicada Life Cycle
The life cycle of a cicada begins when a female lays her eggs, deposited in slits in tree bark or branches. Nymphs hatch from these eggs and drop to the ground. These nymphs then burrow into the soil, commencing their extended subterranean existence.
Underground, cicada nymphs feed on watery sap from tree roots. They can spend anywhere from a few years to over a decade in this underground stage, undergoing several molts as they grow. When they reach their final nymphal instar, they dig their way to the surface, often during late spring or early summer.
Upon emergence, the nymphs climb onto nearby vegetation for their final molt. They anchor themselves and shed their exoskeletons, transforming into winged adult cicadas. This discarded nymphal skin, often found clinging to tree trunks, is a common sight. The adult stage is relatively brief, lasting only a few weeks, and is dedicated to reproduction.
Periodical and Annual Broods
Cicadas exhibit distinct patterns in their emergence, broadly categorized into periodical and annual broods. Periodical cicadas are known for their highly synchronized, mass emergences at fixed intervals of 13 or 17 years. These emergences involve millions of individuals appearing simultaneously, forming “broods.”
This synchronized emergence is considered an evolutionary strategy known as predator satiation. By appearing in overwhelming numbers, periodical cicadas ensure predators cannot consume all individuals, allowing sufficient numbers to survive and reproduce. The genus Magicicada in North America exemplifies this phenomenon.
In contrast, annual cicadas have life cycles that are shorter and less synchronized, ranging from two to five years. While their individual life cycles may still span multiple years, adult annual cicadas emerge every summer, rather than in large, infrequent broods. This staggered emergence means that some individuals of a given species complete their development each year, making them a consistent presence during warmer months.
Ecological Role and Behavior
Male cicadas are known for their loud acoustic displays, which serve as mating calls to attract females. This sound production is achieved through specialized organs called tymbals, located at the base of their abdomen. These tymbals rapidly buckle and unbuckle, creating the distinct buzzing, clicking, or whirring sounds.
While adults feed on xylem sap from trees, their feeding activities cause minimal harm to mature plants. However, female cicadas can cause some damage during oviposition. They use a sharp ovipositor to slit tree branches, creating pockets for their eggs, which can lead to wilting or breakage of branches.
Cicadas also play a significant role in their ecosystems as a food source for predators. During mass emergences, especially of periodical cicadas, they become an abundant, temporary food supply for birds, small mammals, reptiles, and predatory insects. This influx of biomass can influence food web dynamics.