Tettigarctidae is a family of cicadas so ancient and so unlike their familiar relatives that entomologists sometimes call its members “hairy cicadas” or “relict cicadas.” Only two living species survive, both confined to cool, mountainous parts of Australia, making this one of the smallest and most geographically restricted insect families on Earth. Yet the fossil record tells a different story: Tettigarctidae once had a near-global distribution and a lineage stretching back at least to the Middle Jurassic, roughly 165 million years ago. What makes the family especially striking is how its living representatives communicate. Instead of producing the deafening airborne songs most people associate with cicadas, tettigarctids vibrate their bodies and send signals through whatever plant they are sitting on.
The Two Surviving Species
The entire modern diversity of Tettigarctidae fits into a single genus, Tettigarcta, containing two described species: Tettigarcta crinita and Tettigarcta tomentosa. Both live in southeastern Australia, primarily in montane eucalypt forests in Tasmania and parts of the Great Dividing Range on the mainland. Their habitats tend to be cool and wet, and the insects are rarely encountered in the field, which has made basic natural-history observations surprisingly hard to come by.
Physically, the two species look strikingly different from ordinary cicadas. They are covered in fine, dense setae (hence “hairy cicadas”), and their bodies are relatively stout and compact. Their wings, while structured along the same general plan as other cicadoid wings, lack the glassy transparency typical of many singing cicadas and instead can appear somewhat opaque and heavily veined. The overall impression is of an insect that seems to belong to a much earlier era, which, in evolutionary terms, it does.
How Tettigarctids Communicate Without Singing
The defining behavioral difference between Tettigarctidae and the familiar Cicadidae is sound production. Typical cicadas are among the loudest insects alive, generating songs through rapid buckling of specialized structures called tymbals on their abdomens. Those songs travel through the air and can be heard hundreds of meters away. Tettigarctids also possess tymbals, but their tymbal muscles are small and undeveloped compared to those of singing cicadas, and they lack the resonant abdominal air cavity that amplifies sound in Cicadidae. The result is that their tymbal vibrations stay low-intensity and are transmitted through the plant substrate rather than broadcast as airborne noise.
This vibrational mode of signaling is shared by many other groups of hemipteran insects, including leafhoppers, planthoppers, and certain lacewings. Because these signals travel only through the plant and attenuate quickly, they have a very limited broadcast range compared with airborne calls. One practical consequence is that vibrational signaling probably carries less risk of attracting predators and parasitoids than the loud songs of typical cicadas.1Oxford Academic (Annals of the Entomological Society of America). Long-range Acoustical Signals, Phonotaxis, and Risk in the Sexual Pair-Forming Behaviors of Okanagana canadensis and O. rimosa (Hemiptera: Cicadidae) For tettigarctids living at low population densities in montane forest, substrate vibration may be sufficient for mate-finding across short distances while keeping the insects inconspicuous.
An Ancient Lineage With Deep Jurassic Roots
Molecular and fossil evidence agree that the split between Tettigarctidae and Cicadidae is very old. Stem-group fossils of both families have been recovered from the Middle Jurassic Daohugou beds of Inner Mongolia, China, indicating that the two lineages had already diverged by at least 165 million years ago.2PubMed Central. Mesozoic evolution of cicadas and their origins of vocalization and root feeding One molecular timetree analysis has suggested that the tettigarctid basal lineage may be as old as 200 million years, pushing its origins back into the Late Triassic or Early Jurassic.3bioRxiv. Cicada timetree by BEAST v1.X verified the recently and exponentially increasing base substitution rates Either way, the family predates the breakup of Gondwana and the radiation of flowering plants, both of which reshaped insect communities profoundly during the Cretaceous.
The deep age of Tettigarctidae helps explain why the two surviving species in Australia feel so isolated from the rest of cicada diversity. They are not a recently derived offshoot that adapted to a niche; they are survivors of a lineage that was once widespread and has been winnowed down to a single genus on a single continent.
A Rich but Tangled Fossil Record
Despite the family’s present-day rarity, fossils attributed to Tettigarctidae have turned up on several continents. Middle Jurassic deposits in China have yielded multiple species of Shuraboprosbole, a genus diagnosed from well-preserved whole-body specimens.4Geobios. Tettigarctidae (Insecta: Hemiptera: Cicadoidea) from the Middle Jurassic of Inner Mongolia, China Additional Jurassic-age fossils with wing coloration patterns, including dark membranes speckled with light markings and longitudinal stripes, have been described from Chinese deposits, hinting at disruptive camouflage strategies in these ancient insects.5Acta Palaeontologica Polonica. New Jurassic Tettigarctid Cicadas from China with a Novel Example of Disruptive Coloration A fossil from the early Miocene of New Zealand, Paratettigarcta zealandica, represents the first cicadoid fossil from that country and shows wing venation patterns consistent with the subfamily Tettigarctinae, though it differs from both other fossils and the living genus in details like the early divergence of certain wing veins and distinctive pigmentation.6PubMed Central. A new genus and species of tettigarctid cicada from the early Miocene of New Zealand: Paratettigarcta zealandica (Hemiptera, Auchenorrhyncha, Tettigarctidae)
The breadth of this record, spanning China, Myanmar, New Zealand, and potentially other Gondwanan landmasses, shows that Tettigarctidae was not always an Australian endemic. It had a distribution that tracked the ancient supercontinents and only contracted as the family declined and continents drifted apart.
Why “Tettigarctidae” Is Harder to Define Than It Looks
One of the more interesting wrinkles in tettigarctid research is that the family, as traditionally defined to include Mesozoic fossils, turns out to be paraphyletic. Phylogenetic analyses using both morphological and molecular data have shown that several genera long classified as Tettigarctidae, including Macrotettigarcta, Shuraboprosbole, Sanmai, Cretotettigarcta, and Vetuprosbole, may actually sit on the stem lineage leading to modern Cicadidae rather than grouping with the living Tettigarcta.7Nature Communications. Mesozoic evolution of cicadas and their origins of vocalization and root feeding In other words, these fossils look superficially tettigarctid-like because they retain ancestral features shared by all early cicadoids, not because they are close relatives of the living Australian species.
This distinction matters for understanding how the family shrank. If the Mesozoic “tettigarctids” were actually stem cicadids all along, then the true crown-group Tettigarctidae may never have been as diverse as the fossil record appeared to suggest. The family’s modern rarity might reflect a lineage that was always relatively narrow rather than one that suffered a dramatic collapse. The evidence is still being sorted out, and future fossil discoveries, especially well-preserved specimens that show body anatomy rather than just wing venation, will help refine where each genus actually belongs.
What Fossils Reveal About the Origin of Cicada Song
The relationship between Tettigarctidae and Cicadidae has become central to understanding how loud airborne singing evolved in cicadas. Micro-CT scans of mid-Cretaceous cicadoid fossils preserved in Burmese amber have revealed tymbal structures in both males and females of several species, suggesting that tymbals are an ancestral trait of Cicadoidea as a whole, not something that evolved uniquely in the singing cicadas.8Nature Communications. Mesozoic evolution of cicadas and their origins of vocalization and root feeding However, these ancient tymbals differed from those of modern Cicadidae. Their outlines were rounder, and the fossils lacked the tymbal cavity, tympanum, tympanal cavity, and operculum that modern singing cicadas use to amplify and shape their calls.
The implication is that the earliest cicadoids, like modern tettigarctids, communicated through substrate vibration. The full suite of structures needed for loud airborne sound production was assembled step by step over tens of millions of years. One mid-Cretaceous fossil, Pr. xiai, stood out because it preserved a well-developed tymbal muscle and an abdominal cavity that could have served a resonant function, similar to what you see in living Cicadidae rather than Tettigarctidae.9Nature Communications. Mesozoic evolution of cicadas and their origins of vocalization and root feeding This fossil may represent a transitional stage in the evolution of airborne singing, where the basic tymbal was present, the muscles powering it had grown larger, and a resonating chamber had begun to develop, but the full acoustic toolkit of a modern cicada was not yet in place.
Living tettigarctids, then, offer a window into the ancestral condition. Their small tymbal muscles and lack of an air-filled resonating cavity are not degenerate losses; they are the ancestral state from which the spectacular songs of modern cicadas eventually evolved. Every time a summer cicada chorus becomes deafening, you are hearing the outcome of an acoustic arms race that the tettigarctid lineage simply never entered.
Underground Lives and Root Feeding
Like their singing relatives, tettigarctid nymphs live underground, using piercing-sucking mouthparts to feed on plant roots. Fossil evidence confirms that this subterranean lifestyle was established in cicadoids by at least the mid-Cretaceous. Final-instar nymphal fossils and shed exoskeletons from that period show the characteristic fossorial forelegs, broadened and heavily spined for digging, along with elongate mouthparts suited to piercing root tissue.10Nature Communications. Mesozoic evolution of cicadas and their origins of vocalization and root feeding Root feeding is therefore another ancestral trait shared by both families, not something that evolved separately in each lineage.
Morphological comparisons of nymphal fossils have revealed differences between specimens closer to the tettigarctid lineage and those closer to the cicadid lineage. Tettigarctid-type nymphs have secondary apical tibial teeth on the front legs that are much longer and more robust, resembling oversized pliers, while cicadid-type nymphs have smaller, blunter secondary teeth.11Nature Communications. Mesozoic evolution of cicadas and their origins of vocalization and root feeding These differences in digging anatomy suggest that the two families may have diverged in the depth or type of soil they burrowed through, or the kinds of roots they targeted, though direct ecological observations of living tettigarctid nymphs are almost nonexistent.
A Quirk in the Mitochondrial Genome
Modern sequencing has added a molecular dimension to understanding Tettigarctidae’s distinctiveness. A study that sequenced one hundred cicada mitochondrial genomes found that T. crinita, the sole tettigarctid included, had an unusual change in its transfer RNA for alanine: the anticodon had shifted from the ancestral TGC to CGC, a substitution not seen in any of the Cicadidae species examined or in the fruit fly reference genome.12Journal of Heredity. One Hundred Mitochondrial Genomes of Cicadas Anticodon changes in transfer RNAs are relatively rare events, and this one underscores how long the tettigarctid and cicadid lineages have been evolving independently. Whether this substitution has any functional consequence for the insect’s mitochondrial protein synthesis is unknown, but it adds to the list of molecular markers that distinguish the family.
Why These Cicadas Are So Hard to Study
Despite their evolutionary importance, tettigarctids remain among the least-studied cicadoids. Several factors conspire against field research. Both living species occur at low densities in relatively remote montane habitats. Their vibrational communication makes them difficult to detect; you cannot simply follow a loud song to find one. Adults are not attracted to lights, and their emergence patterns are poorly documented. Most museum specimens were collected opportunistically rather than through targeted surveys, so basic data on population size, seasonal activity, host-plant preferences, and nymphal development time are patchy at best.
Conservation concern has been raised informally, but neither species has been formally assessed by the IUCN as of recent evaluations. Climate change poses a theoretical risk because montane species in Australia face shrinking habitat as temperatures climb, but without baseline population data it is hard to quantify the threat. For now, Tettigarctidae occupies an uncomfortable position in entomology: universally acknowledged as scientifically important, yet still largely a mystery in the field.
Wing Venation as a Taxonomic Workhorse
Because many tettigarctid fossils are preserved only as wing impressions or compressions, wing venation has historically been the primary tool for classifying species within the family. Tettigarctid forewings typically have a characteristic pattern of vein branching: the radius forks early, the media is three-branched, and the cubital veins diverge near or just beyond the nodal line. Variations in details like the number of apical cells, the length of the subcostal cell, and the point at which particular veins bifurcate are what separate genera and species.
The Miocene New Zealand species Paratettigarcta zealandica illustrated both the utility and the limits of this approach. Its wing venation was clearly tettigarctine, but it differed from the living genus in several structural details, including a parallel-sided subcostal cell and an unusually early bifurcation of vein M in the hindwing.13PubMed Central. A new genus and species of tettigarctid cicada from the early Miocene of New Zealand: Paratettigarcta zealandica (Hemiptera, Auchenorrhyncha, Tettigarctidae) These differences were enough to warrant a new genus, but they also highlight a broader challenge: wing venation alone cannot always resolve whether a fossil belongs to the tettigarctid crown group or to a stem lineage. The paraphyly problem discussed above is partly a consequence of relying too heavily on wing characters that may be shared ancestral traits rather than indicators of true relatedness.
Coloration Patterns in Jurassic Fossils
One of the more unexpected findings in tettigarctid paleontology is that some Jurassic fossils preserve wing coloration in enough detail to interpret possible ecological function. Specimens from Chinese deposits show dark wing membranes marked with irregular light speckles and longitudinal stripes.14Acta Palaeontologica Polonica. New Jurassic Tettigarctid Cicadas from China with a Novel Example of Disruptive Coloration This kind of patterning has been interpreted as disruptive coloration, a camouflage strategy where contrasting patches break up the outline of the body against a visually complex background like bark or leaf litter.
Modern tettigarctids are cryptically colored and spend most of their adult lives on tree trunks and branches, so the presence of disruptive wing patterning in their Jurassic relatives is consistent with a long evolutionary history of relying on crypsis rather than flight agility to avoid predators. It also suggests that the selective pressures shaping tettigarctid appearance have been remarkably stable across 165 million years, even as the forests around them changed from gymnosperm-dominated woodlands to angiosperm-rich ecosystems.
The Broader Picture of Cicadoid Diversity
With roughly 3,000 described species, Cicadidae dominates modern cicadoid diversity so thoroughly that it is easy to forget the superfamily ever had another branch. Tettigarctidae is the only other extant family in Cicadoidea, and its two species represent less than 0.1 percent of the superfamily’s living richness. That asymmetry invites the question of what went differently for the two lineages.
One plausible factor is the evolution of airborne acoustic signaling. The loud calls of Cicadidae allow individuals to locate mates across long distances, which may have facilitated speciation by enabling divergence in call structure among populations that were otherwise geographically overlapping. Vibrational signals, by contrast, are inherently short-range and may limit opportunities for the kind of signal-based reproductive isolation that drives speciation in acoustic insects. Whether this hypothesis holds up to rigorous testing remains to be seen, but it offers a framework for thinking about why one lineage radiated explosively while its sister lineage remained depauperate.
Another factor could simply be geography. Australia was separated from other landmasses for tens of millions of years, and whatever tettigarctid diversity existed on other continents evidently did not survive into the modern era. The New Zealand Miocene fossil shows the family persisted there until at least 20 million years ago, but no living descendants are known outside Australia. What eliminated tettigarctids from the rest of the world, whether competition, climate shifts, or habitat loss, remains an open question.