Blattoidea

Blattoidea is a superfamily of insects within the order Blattodea (superorder Dictyoptera), encompassing a diverse array of cockroaches and the termite clade, notable for their roles in decomposition and as some of the most ancient extant insect lineages.^[1] This group originated during the Jurassic period and is characterized by hemimetabolous development, with nymphs resembling wingless adults, and adaptations for terrestrial life including robust exoskeletons and mouthparts suited for omnivorous or lignivorous diets.^[2] Blattoidea comprises over 4,000 species (as of 2024) across five cockroach families—Blattidae (over 600 species), Anaplectidae (114 species), Cryptocercidae (11 species), Lamproblattidae (around 10 species), and Tryonicidae (around 20 species)—plus approximately 3,000 termite species in the suborder Isoptera (now Termitoidae), totaling over 4,000 described species worldwide. ^[3]^[4] Phylogenetically, Blattoidea forms one of three major clades in Blattodea, alongside Blaberoidea and Corydioidea, with recent phylotranscriptomic analyses confirming its monophyly and positioning it as sister to Corydioidea; internally, it includes the basal cockroach families Blattidae, Tryonicidae, and Lamproblattidae, with Anaplectidae and the subsocial wood-feeding Cryptocercidae sister to the eusocial termites.^[1]^[5] These insects exhibit significant ecological importance, particularly termites, which are key decomposers of cellulose-rich materials like wood, facilitating nutrient cycling in ecosystems, while some cockroach species in Blattidae, such as the American cockroach (Periplaneta americana), are synanthropic pests in human habitats.^[2] Evolutionarily, Blattoidea highlights transitions from solitary to subsocial and eusocial behaviors, with Cryptocercidae serving as a model for understanding termite origins due to shared gut symbionts and parental care.^[1] Species distribution spans tropical to temperate regions globally, with highest diversity in the tropics, and the order Blattodea has persisted since the Carboniferous, with Blattoidea adapting to diverse niches from soil litter to structural wood.^[5]

Taxonomy and Phylogeny

Classification

Blattoidea is a superfamily within the order Blattodea, part of the larger superorder Dictyoptera in the class Insecta. This placement reflects the monophyletic grouping of cockroaches and termites, with Blattodea encompassing all extant species in this lineage. The full hierarchical classification is as follows: Kingdom Animalia, Phylum Arthropoda, Class Insecta, Order Blattodea, Superfamily Blattoidea.^[6]^[2] The superfamily Blattoidea includes the "higher" cockroaches and termites, distinguished from other Blattodea superfamilies such as Blaberoidea and Corydioidea based on molecular and morphological phylogenies. It comprises approximately 3,960 species across multiple families, representing a significant portion of Blattodea diversity. Key families within Blattoidea are Anaplectidae, Blattidae, Cryptocercidae, Lamproblattidae, and Tryonicidae, with termites (traditionally classified as Isoptera) nested as the sister group to Cryptocercidae.^[2]^[5]^[7]^[3] Phylogenetic analyses support Blattoidea as a robust clade, with recent phylotranscriptomic studies resolving (Blattidae + Tryonicidae) as sister to ((Lamproblattidae + Anaplectidae) + (Cryptocercidae + Isoptera)). This structure has been refined through multi-locus molecular data, resolving previous uncertainties in family-level relationships. Termites are now treated as an epifamily (Termitoidae) within Blattodea rather than a separate order, emphasizing their evolutionary proximity to wood-dwelling cockroaches in Cryptocercidae.^[2]^[5]^[7]^[1]

Taxon	Description	Representative Families
Blattidae	Largest family of typical cockroaches, including cosmopolitan pests; subfamilies include Blattinae and Polyzosteriinae.	Blattidae (e.g., genus Periplaneta)^[5]
Lamproblattidae	Small family of forest-dwelling cockroaches from the Old World tropics.	Lamproblattidae^[2]
Tryonicidae	Australian endemic family with robust, flightless species.	Tryonicidae^[5]
Anaplectidae	Rare, litter-inhabiting cockroaches with specialized morphology.	Anaplectidae^[2]
Cryptocercidae + Isoptera	Wood-feeding clade; Cryptocercidae includes damp-wood cockroaches, while Isoptera encompasses all termite families (e.g., Rhinotermitidae, Termitidae).	Cryptocercidae, Termitidae^[7]^[5]

Evolutionary Relationships

Blattoidea represents one of the three principal superfamilies within the order Blattodea, alongside Blaberoidea and Corydioidea, with recent molecular phylogenies recovering it as monophyletic and sister to Corydioidea, forming the clade Solumblattodea. This relationship is supported by analyses of transcriptomic data, which place Blattoidea + Corydioidea as diverging from Blaberoidea in the Jurassic.^[1] Earlier mitogenomic studies recovered a different topology, with Corydioidea diverging from (Blattoidea + Blaberoidea) around 210 million years ago (95% CI: 180.5–244.3 Ma).^[2] Within Blattoidea, recent phylotranscriptomic analyses recover (Blattidae + Tryonicidae) as the sister group to the remaining families, with (Lamproblattidae + Anaplectidae) sister to (Cryptocercidae + Termitoidae). This structure is robustly supported by phylogenomic datasets, highlighting synapomorphies such as specialized gut microbiomes and xylophagous diets in the derived lineages. The sister-group relationship between Cryptocercidae and Termitoidae (termites) is a key insight, positioning termites as phylogenetically nested within cockroaches rather than a separate order, with their divergence estimated at approximately 150 million years ago in the Early Cretaceous based on fossil-calibrated molecular clocks.^[2]^[1] These evolutionary relationships underscore the adaptive radiation of Blattoidea, with transitions from free-living detritivory in basal groups like Blattidae to subsocial wood-feeding in Cryptocercidae and eusociality in Termitoidae, driven by symbiont-mediated digestion of lignocellulose. Recent integrative analyses incorporating mitochondrial genomes from 67 ingroup taxa reinforce the monophyly of Blattoidea and its sub-clades, resolving previous uncertainties around Anaplectidae's placement sister to Lamproblattidae with maximum likelihood support exceeding 95%.^[3] Overall, these findings from multi-locus and phylotranscriptomic approaches provide a stable framework for understanding Blattoidea's role in Blattodea diversification, bridging molecular and fossil evidence from the Mesozoic era.^[1]^[2]

Morphology and Biology

Physical Characteristics

Blattoidea, encompassing the cockroach lineages within the order Blattodea, exhibit a dorsoventrally flattened body adapted for navigating tight spaces and rapid movement. The body is divided into three tagmata: head, thorax, and abdomen. The head is orthognathous or hypognathous, featuring large compound eyes and long, filiform antennae that serve sensory functions, often exceeding the body length in some species. The thorax bears a prominent pronotum forming a shield-like structure that partially conceals the head, with three pairs of jointed legs specialized for running—featuring five-segmented tarsi and spiny tibiae for traction. Wings, when present, consist of thickened forewings (tegmina) and pleated, membranous hindwings folded beneath; however, wing reduction is common in many species. The abdomen is elongate and oval, terminating in short, multi-segmented cerci, with a robust exoskeleton providing protection and flexibility.^[8]^[9] In contrast, termites, phylogenetically nested within Blattodea as a derived eusocial clade, display a more generalized, soft-bodied morphology suited to colonial wood-dwelling lifestyles, though sharing core blattoid features like chewing mouthparts and a broad thorax-abdomen junction. Termite castes exhibit pronounced dimorphism: workers and soldiers are pale, blind or with reduced eyes, and wingless, with workers having oval, beaded antennae and soldiers featuring enlarged, sclerotized heads with asymmetrical mandibles for defense. Alates (winged reproductives) possess two pairs of equal-length, membranous wings with similar venation, compound eyes, and ocelli, which are shed post-swarming. Queens undergo extreme physogastry, with the abdomen swelling dramatically—up to 14 cm in length in some species like Macrotermes—for massive egg production, while kings remain smaller and mobile. Legs are ambulatory, less cursorial than in cockroaches, reflecting subterranean habits.^[10]^[11] Shared morphological traits between cockroaches and termites underscore their close evolutionary ties, including filiform antennae, biting mandibles, and a lack of a constricted waist, distinguishing them from other dictyopterans like mantises. Variations within Blattoidea include fossorial adaptations in some cockroaches, such as shortened, wider bodies and robust forelegs for burrowing, while termite soldiers show specialized head shapes (phragmotic or nasute) for nest defense. Overall body sizes range from 3 mm in small cockroaches to over 90 mm in larger species, with termites generally smaller except for physogastric queens.^[8]^[9]^[11]

Reproduction and Development

Blattoidea, encompassing cockroaches and termites, exhibit hemimetabolous development, characterized by incomplete metamorphosis with egg, nymph, and adult stages, though termites display additional eusocial caste differentiation. Reproduction is primarily sexual, with females producing eggs enclosed in protective oothecae in cockroaches, while termites feature complex breeding systems involving primary alate reproductives and secondary neotenics. Embryonic development occurs within eggs, influenced by environmental factors like temperature, and postembryonic growth involves multiple nymphal instars before maturity.^[12]^[13] In cockroaches, reproduction is oviparous, with females forming oothecae—elongated capsules containing multiple eggs—that are either carried externally until hatching or deposited in sheltered locations. For instance, in the American cockroach (Periplaneta americana), mated females produce an ootheca every 4 days on average, each containing 12–16 eggs, with embryonic development lasting approximately 35 days at 29°C; unmated females reproduce parthenogenetically but at a slower rate, producing oothecae every 10 days with lower hatching success (45% versus 81% in mated individuals).^[12] Embryogenesis in cockroaches involves syncytial cleavage followed by blastoderm formation, with species like the German cockroach (Blattella germanica) showing a direct-differentiating blastoderm without a uniform peripheral layer typical of many insects; nuclear divisions lead to germband formation by about 14% of development (around day 3.5 at standard conditions), featuring sequential abdominal segmentation and near-simultaneous gnathal-thoracic segment formation.^[14] Postembryonic development includes 7–13 nymphal instars, varying by species and conditions; in P. americana, 14 instars occur under optimal group housing, with secondary sexual traits emerging from the 11th instar, culminating in adult eclosion after 200–600 days depending on temperature and nutrition.^[12] Termites, as eusocial members of Blattoidea, have reproductive strategies centered on colony-level propagation, with primary reproductives (winged alates) initiating colonies via swarming and tandem running, followed by dealation and ootheca production similar to cockroaches but adapted for subterranean or wood-dwelling nests. Queens lay eggs continuously after colony establishment, with embryonic development mirroring cockroach patterns but often in humid nest environments to support rapid hatching.^[13] Secondary reproduction via neotenics—immature-like reproductives derived from nymphs or workers—arises upon primary queen death, enhancing colony survival; these occur in over 60% of lower termite genera (e.g., Rhinotermitidae like Reticulitermes flavipes) but only 13% of higher termite genera (Termitidae), with types including brachypterous nymphoids and apterous ergatoids that mate within the colony.^[15] Parthenogenesis, particularly asexual queen succession, is documented in at least six species (e.g., Reticulitermes speratus), where queens produce female neotenics thelytokously, allowing unisexual lineage perpetuation in mixed-sex societies.^[13] Developmentally, termite nymphs progress through 4–30+ instars to alate maturity, with caste determination (workers, soldiers, reproductives) regulated by juvenile hormones and colony needs; neotenic differentiation can accelerate under orphaning conditions, as seen in R. speratus where male neotenics promote further reproductive caste formation.^[15]

Ecology and Distribution

Habitats and Lifestyles

Blattoidea, encompassing specific cockroach families and termites, primarily occupy tropical and subtropical habitats worldwide, with some Blattidae species extending to temperate zones and urban settings through synanthropic adaptations. The majority of species thrive in hot, humid environments like tropical forests where organic detritus is abundant, though distributions vary by family.^[16] These insects are predominantly detritivores, relying on dead plant material for sustenance, which underscores their role in decomposition and nutrient recycling across ecosystems.^[16] Cockroaches within Blattoidea exhibit adaptability, inhabiting microhabitats such as forest floors, tree canopies, hollow trunks, and areas with accumulated organic matter, particularly in tropical regions.^[17] Many species are nocturnal foragers, emerging at night to consume decaying vegetation, fungi, or small invertebrates. In urban environments, synanthropic species such as Periplaneta americana exploit human structures for shelter and food waste, demonstrating behavioral flexibility that includes aggregation pheromones to coordinate group movements and resource location.^[18] Certain tropical cockroaches, including Salganea species in Cryptocercidae, live gregariously in decaying logs, relying on symbiotic gut flagellates for wood digestion, a trait that parallels early evolutionary steps toward termite sociality.^[17] The ecology of other Blattoidea families is less studied: Anaplectidae species are found in leaf litter and under bark in Asian and Neotropical forests; Lamproblattidae inhabit Central and South American woodlands; and Tryonicidae include wood-feeding and synanthropic species in South America.^[5] Termites, as the eusocial sister group to cockroaches, predominantly inhabit tropical and subtropical regions, constructing nests that vary from subterranean tunnels and epigeous mounds to arboreal structures in trees or dry/damp wood.^[19] Their lifestyles revolve around caste-based colonies, where workers forage collectively using pheromone trails to access cellulose-rich resources like wood or grass, aided by obligate gut symbionts that enable efficient digestion.^[19] For instance, subterranean species such as Reticulitermes speratus in temperate Japan build extensive underground galleries for foraging, while invasive Coptotermes formosanus in the southeastern United States tunnels through structural wood, forming colonies of millions that enhance soil aeration but pose economic threats.^[19] Overall, termite societies emphasize cooperative nest maintenance and defense, with reproductives (kings and queens) achieving exceptional longevity—up to decades—facilitating sustained colony growth in stable, resource-abundant habitats.^[20]

Ecological Roles

Blattoidea, encompassing cockroaches and termites, serve as essential decomposers in terrestrial ecosystems, facilitating the breakdown of organic matter and nutrient recycling. Members of this superfamily process dead plant material, animal remains, and excrement, returning vital nutrients like nitrogen and carbon to the soil, which supports plant growth and maintains ecosystem productivity.^[2] Their activities contribute to soil aeration and organic matter incorporation, enhancing soil fertility across diverse habitats from forests to arid regions.^[21] Cockroaches within Blattoidea act as opportunistic scavengers, consuming a wide range of decaying organic substances, including cellulose-rich plant litter and fecal matter, which aids in the initial stages of decomposition. This role is particularly pronounced in forest floors and urban environments, where they help mitigate waste accumulation and promote microbial activity in soil.^[22] For instance, species in the genus Periplaneta feed on leaf litter and organic debris, accelerating nutrient release and supporting detritivore food webs.^[23] Additionally, cockroaches serve as prey for numerous predators, including birds, reptiles, and small mammals, thereby integrating into broader trophic dynamics and bolstering biodiversity.^[24] Termites, the eusocial counterpart in Blattoidea, function as ecosystem engineers through mound construction and wood decomposition, profoundly influencing soil structure and water retention in tropical and subtropical regions. They process substantial volumes of lignocellulosic material—up to 30% of net primary production in some savannas—driving carbon and nitrogen cycles while emitting greenhouse gases like methane and carbon dioxide as byproducts.^[25] Termite mounds concentrate nutrients, creating fertile microhabitats that foster plant diversity and inhibit desert encroachment in semi-arid areas.^[26] In degraded landscapes, their bioturbation improves soil porosity and crop yields, underscoring their restorative potential in agroecosystems.^[27]

Diversity and Families

Cockroach Families

The cockroach families within Blattoidea encompass approximately 1,200 valid species distributed across five genera-rich families.^[28] These families exhibit diverse morphologies, habitats, and behaviors, ranging from wood-dwelling subsocial species to fossorial sand-dwellers and urban pests. Modern taxonomy recognizes 12 extant cockroach families, classified into three superfamilies: Blattoidea, Blaberoidea, and Corydioidea, based on phylogenetic analyses of mitogenomes, nuclear genes, and morphological traits such as spermathecae structure and wing venation.^[1] This classification reflects a paraphyletic arrangement where termites (Termitoidae) nest within Blattoidea as the sister group to Cryptocercidae, highlighting the shared evolutionary history of cockroaches and termites.^[2] The superfamily Blattoidea includes five cockroach families and represents the "true" cockroaches, characterized by robust bodies, often with prominent ocelli and a more primitive wing structure compared to other groups. Blattidae, the type family, is one of the largest and most widespread, containing over 50 genera and around 500 species, including notorious pests like the American cockroach (Periplaneta americana) and oriental cockroach (Blatta orientalis); these are typically large, winged insects adapted to humid, decaying organic matter in tropical and subtropical regions.^[1] Lamproblattidae comprises three genera and about 10 species, primarily from Southeast Asia and Australia, featuring shiny, metallic exoskeletons and a burrowing lifestyle in leaf litter.^[5] Tryonicidae, with seven genera and 17 species, is endemic to Australia and New Guinea, known for its elongated bodies and adaptation to arid environments, often burrowing in soil or under bark.^[5] Anaplectidae includes a single genus (Anaplecta) with approximately 112 species, small and winged, distributed in tropical Asia and Africa, notable for their reduced ocelli and association with ant nests as myrmecophiles.^[1] Cryptocercidae, a monogeneric family (Cryptocercus) with around 20 species, is unique for its subsocial behavior, including parental care and wood-boring habits in temperate forests of North America, Asia, and Europe; it serves as the closest living relative to termites, sharing symbiotic gut protozoa for cellulose digestion.^[2] These families collectively illustrate the evolutionary success of cockroaches within Blattoidea, with most diversity in tropical regions, though urban species have achieved global distribution via human activity. Phylogenetic studies underscore the monophyly of most families, with ongoing revisions based on molecular data.^[2]

Termite Families

Termites, classified within the epifamily Termitoidae of the Blattodea order (formerly Isoptera), comprise approximately 3,000 described species distributed across 12 recognized families in the most recent phylogenomic classification.^[29] These families reflect a deep evolutionary split into basal "lower termites," which rely on symbiotic protists for cellulose digestion, and more derived "higher termites" in the family Termitidae, which use endogenous microbes.^[29] The phylogeny, reconstructed from ultraconserved elements (UCEs) across 135 species, reveals monophyletic families with rapid diversification in the Neoisoptera clade, encompassing all families except the most basal Mastotermitidae.^[29] This classification addresses previous paraphyly in Rhinotermitidae by elevating subfamilies to family status, emphasizing morphological traits like soldier mandibles, gut anatomy, and caste systems.^[29] The basal family Mastotermitidae contains a single species, Mastotermes darwiniensis, in one genus, restricted to northern Australia and nearby islands.^[29] These large, primitive termites inhabit wood and soil interfaces, featuring true workers and soldiers with pincer-like mandibles; they retain ancestral traits like ovipositor presence in queens and alate brachypterous wings.^[29] Evolutionarily, Mastotermitidae represents the earliest diverging extant lineage, sister to all other termites, highlighting their relictual status.^[29] Archotermopsidae includes dampwood termites like Zootermopsis species, primarily in western North America, with a few in Asia.^[29] They nest in decaying coniferous wood, possessing true workers and soldiers with symmetrical mandibles; colonies are small and perennial.^[29] This family occupies an early position in the Neoisoptera clade, bridging basal and derived forms through their wood-dwelling habits and protist symbionts.^[29] Stolotermitidae, with genera like Stolotermes, occurs in southern Australia, New Zealand, and parts of South America.^[29] These wood-feeders lack true workers, using pseudergates instead, and feature soldiers with falcate mandibles; they are adapted to temperate forests.^[29] Phylogenetically, they diverge early within Neoisoptera, exemplifying Gondwanan distributions.^[29] Hodotermitidae comprises harvester termites such as Hodotermes and Anacanthotermes, distributed in Africa and southern Eurasia.^[29] They forage aboveground on grasses and seeds, with true workers and soldiers bearing saber-like mandibles; nests are mound-based in arid regions.^[29] This family is basal in Neoisoptera, notable for their shift from wood to litter feeding.^[29] Kalotermitidae, the drywood termites, is one of the most species-rich basal families, with hundreds of species in genera like Kalotermes and Cryptotermes, found pantropically and into temperate zones.^[29] They infest sound wood without soil contact, lacking true workers and featuring soldiers with small, conical heads; colonies are small and independent.^[29] Evolutionarily, they represent a core lower termite lineage with worldwide dispersal, often invasive.^[29] Stylotermitidae is a small family with one genus, Stylotermes, limited to Southeast Asia.^[29] These wood-dwellers lack true workers, with soldiers showing unique stylate antennae; they inhabit rotten logs in humid forests.^[29] Their position near Kalotermitidae underscores Southeast Asian endemism in early Neoisoptera.^[29] Serritermitidae, containing only Serritermes in the Neotropics, specializes in soil feeding.^[29] Soldiers have serrated mandibles for defense, and colonies build arboreal carton nests; they associate with fungi.^[29] This monotypic family diverges just before higher termites, linking lower and soil-feeding strategies.^[29] Hodotermopsidae, with Hodotermopsis species, is confined to Japan and China.^[29] These dampwood termites have true workers and soldiers with piercing mandibles, nesting in moist wood.^[29] They form a basal Neoisoptera clade, retaining primitive dampwood adaptations in East Asia.^[29] The revised Rhinotermitidae (sensu novo) includes five genera like Rhinotermes and Acorhinotermes, pantropical with ~200 species.^[29] They are subterranean wood-feeders with inflated clypeus in imagoes and soldiers featuring elongated labrum; many are economic pests.^[29] Phylogenetically, this restricted family is monophyletic within early Neoisoptera post-revision.^[29] Heterotermitidae (new status), with genera Coptotermes, Heterotermes, and Reticulitermes, totals ~300 species globally, especially invasive in temperate and subtropical areas.^[29] Subterranean nesters, they have soldiers with katana-shaped mandibles and build extensive tunnel systems; they rely on protist symbionts.^[29] Elevated from Rhinotermitidae, they form a distinct early Neoisoptera lineage.^[29] Psammotermitidae (new status) encompasses Psammotermes and Prorhinotermes, ~50 species in arid Africa, Arabia, and islands.^[29] Adapted to dry soils, they feature flat pronota and soldiers with 3:2:2 tibial spurs; nests are subterranean or in wood debris.^[29] This family resolves paraphyly in former Rhinotermitidae, positioned early in Neoisoptera.^[29] Termitogetonidae (new status), with two Termitogeton species in Southeast Asia and Pacific islands, are hairy, flattened wood-feeders.^[29] Soldiers have robust mandibles, and colonies are small; their dense pilosity aids in humid environments.^[29] They represent a terminal split in the revised Rhinotermes group within Neoisoptera.^[29] The dominant Termitidae, higher termites, account for ~75% of all species (~2,250), across 18 monophyletic subfamilies like Termitinae and Macrotermitinae, in numerous genera, pantropical.^[29] They exhibit diverse diets (soil, fungus, grass) without protists, using bacterial symbionts; soldiers vary widely (e.g., nasute in Nasutitermitinae), and nests include massive mounds.^[29] As the most derived family, Termitidae underwent rapid radiation, driving termite global diversity and ecological impact.^[29]

Evolution and Fossil Record

Origins and Timeline

Blattoidea represents a monophyletic superfamily within the order Blattodea, encompassing the families Blattidae, Tryonicidae, Lamproblattidae, Anaplectidae, Cryptocercidae, and Isoptera (termites).^[2] This group originated through divergence from other Blattodea lineages, such as Blaberoidea and Corydioidea, during the Late Triassic to Early Jurassic period. Phylogenetic analyses indicate that the Blattoidea clade split from Blaberoidea approximately 198 million years ago (Ma), with a 95% confidence interval of 173–229 Ma.^[2] Within Blattoidea, Blattidae represents the earliest diverging lineage, emerging around 178 Ma (155–204 Ma).^[2] The close relationship between Cryptocercidae (wood-dwelling cockroaches) and Isoptera highlights termites' evolutionary origin from within cockroach-like ancestors, with their last common ancestor dated to about 146 Ma (137–164 Ma) in the Early Cretaceous.^[2]^[30] The broader origins of Blattoidea trace back to the early diversification of Blattodea, which split from its sister order Mantodea around 263 Ma in the Early Permian.^[30] Crown-group Blattodea, including Blattoidea, arose approximately 205 Ma (184–226 Ma) in the Late Triassic, marking the onset of modern blattodean forms; however, more recent mitogenomic analyses suggest younger crown ages around 112 Ma for Blattodea and 103 Ma for Blattoidea, reflecting debates in fossil calibration and data types.^[30]^[31] Most major Blattoidea subgroups, such as Anaplectidae and the Lamproblattidae-Tryonicidae clade, diversified during the Jurassic to Cretaceous transition, around 155 Ma (133–179 Ma).^[2] Eusociality in termites, a key innovation within Blattoidea, evolved after the Cryptocercidae-Isoptera divergence, no earlier than 134 Ma.^[30] These molecular divergence estimates are supported by phylogenomic data from over 1,000 nuclear genes across 119 Blattodea species, providing robust calibration against vetted fossils.^[30] The fossil record of Blattoidea aligns with these molecular timelines but distinguishes between stem-group "roachoids" and crown taxa. Stem-Blattodea fossils, resembling early blattoids, appear in the Late Carboniferous (Pennsylvanian, ~320–300 Ma), but these represent primitive dictyopterans rather than modern Blattoidea.^[32] The oldest crown-Blattodea fossils date to the Early Cretaceous (~140 Ma), including cockroach-like forms from the Valanginian stage.^[30] For Blattoidea specifically, the earliest definitive cockroach fossils (e.g., in Blattidae) are from the Early Cretaceous (~125 Ma), while termite fossils first appear in the Late Jurassic (~150 Ma), with rapid diversification by the Early Cretaceous.^[33]^[34] Key calibrating fossils include fossils from the related superfamily Corydioidea, such as Cretaholocompsa montsecana (~125 Ma), and early termites like Archeorhinotermes rossi (~100 Ma).^[30] This record underscores Blattoidea's radiation during the Mesozoic, coinciding with angiosperm expansion and ecological opportunities in decaying wood habitats.^[30]

Notable Fossils

The fossil record of Blattoidea, encompassing both cockroaches and termites, spans from the Late Carboniferous to the present, with stem-group forms appearing earlier than crown taxa. Early fossils, often classified as "roachoids," represent transitional forms between primitive Dictyoptera and modern blattoids, providing insights into the group's diversification during the Paleozoic. These specimens, preserved in coal measures and shales, exhibit large body sizes and wing venation patterns that foreshadow later adaptations, though they are not true crown-group members.^[35] Among the earliest notable cockroach fossils is Alderblattina simmsi, discovered in the Charmouth Mudstone Formation of Dorset, United Kingdom, dating to the Early Jurassic Toarcian stage approximately 180 million years ago. This well-preserved specimen, featuring detailed wing structures and coloration patterns, represents one of the oldest unambiguous cockroach species and highlights the persistence of Mesozoic blattodean morphologies.^[36] Complementing this, Cretaholocompsa montsecana from the Barremian-aged lithographic limestones of Montsec, Spain (about 125 million years old), stands as the oldest known fossil of the crown-group family Corydiidae in the superfamily Corydioidea. Its tegmen venation provides strong phylogenetic evidence for calibrating early divergences within modern cockroach lineages.^[37] For termites, the oldest body fossils are Mastotermes nepropadyom and Santonitermes transbaikalicus, both from the Upper Jurassic-Lower Cretaceous boundary deposits (Tithonian or Berriasian) at Chernovskie Kopi in Transbaikalian Russia, approximately 150-145 million years old. These specimens, preserved in sediments, extend the known range of Isoptera by at least 15 million years and represent the earliest direct evidence of termite eusociality, with Mastotermes nepropadyom linking to the primitive family Mastotermitidae.^[34] Another significant find is a termite alate from Early Cretaceous Burmese amber (about 100 million years old), containing preserved gut protists that demonstrate ancient microbial mutualism, marking the oldest such record in animals.^[38] Later notable fossils include large nest structures suggestive of advanced termite behavior. More recently, specimen NMV P344746, a wooden termite nest fragment from the Early Cretaceous Strzelecki Group near Inverloch, Victoria, Australia (approximately 127 million years old), represents the continent's oldest termite trace fossil and one of the largest preserved nests globally, revealing wood-eating habits in polar forest ecosystems.^[39] Eocene amber deposits yield exceptional preservation of Blattoidea, such as “Gyna” obesa from the Menat site in France (52 million years old), the oldest stem Blaberidae cockroach, redescribed with high-resolution imaging to support divergence estimates. Similarly, Baltic and Dominican ambers from the Eocene (44-38 million years old) contain paired termite imagoes in mating positions, like Electrotermes affinis, offering rare glimpses into ancient reproductive behaviors unchanged over tens of millions of years.^[37]^[40]