Batesian insect-insect mimicry-related explosive radiation of ancient alienopterid cockroaches

Alienopterix santonicus sp. n., a metallic cockroach from the Late Cretaceous ajkaite amber (Bakony Mts, western Hungary) documents Alienopteridae within the Mesozoic Laurasia

Cockroaches (Blattaria s. str.) were documented from numerous amber localities around the world, representing both extinct and extant families. Alienopteridae is an extinct cockroach family known only from the Cretaceous of Gondwana (Brazil, Botswana, Myanmar amber) and the Cenozoic of North America. Alienopterix santonicus sp. n. from the Late Cretaceous amber of the Ajka Coal Formation (Bakony Mts, western Hungary) extends the rich geographical distribution of the family into Laurasia during the Mesozoic. As a member of the presumably pollinator cohort Alienopteridae, this species could have played an important role in the Ajka Coal ecosystem during the Santonian. The microrectangular structures of the forewing suggest that the new species likely possessed a metallic colouration already known from the group. Combined with the disruptive body pattern this could have served as an advanced camouflage. The microrectangular structures of the forewing were compared to integument microstructures of extant insects with metallic colouration. Various arthropod taxa are already known from ajkaite, and the new discovery further emphasizes the importance of this amber.

Aposematic coloration from Mid-Cretaceous Kachin amber

Aposematic coloration is among the most diverse antipredator strategies, which can signal unpleasantness of organisms to potential predators and reduce the probability of predation. Unlike mimesis, aposematic coloration allows organisms to warn their predators away by conspicuous and recognizable colour patterns. However, aposematism has been a regular puzzle, especially as the long-term history of such traits is obscured by an insufficient fossil record. Here, we report the discovery of aposematic coloration in an orthopteran nymph from Mid-Cretaceous Kachin amber (99 million years old). It is attributed to the extinct family Elcanidae and erected as a new genus identified by conspicuous dark/light-striped coloration, four apical spurs on the metatibia, a two-segmented metatarsus and unsegmented stylus. It represents the first fossil orthopteran preserved with aposematic coloration from the Mesozoic, demonstrating that orthopterans had evolved aposematism by the Mid-Cretaceous. Our findings provide novel insights into the early evolution of anti-predator strategies among orthopterans. Together with mimesis, debris-carrying camouflage and aposematism previously reported, our findings demonstrate the relative complexity of prey-predator interactions in the Mesozoic, especially in the Mid-Cretaceous Kachin amber forest. This article is part of the theme issue 'The impact of Chinese palaeontology on evolutionary research'.

A new cockroach (Blattodea, Corydiidae) with pectinate antennae from mid-Cretaceous Burmese amber

A new species of fossil cockroach, Fragosublattapectinata gen. et sp. nov., is described from mid-Cretaceous Burmese amber. The new species is assigned to the family Corydiidae based on the following combination of characters: pronotum with tubercles, tegmina obovate with smallish anal region and spinules on the antero-ventral margin of the front femur (type C1). The new species is the second reported cockroach with ramified antennae. This finding broadens the diversity of Blattodea in mid-Cretaceous Burmese amber and provides further evidence of convergent evolution for antennal structures among different insect lineages.

Neotropical Melyroidea group cockroaches reveal various degrees of (eu)sociality

Eusociality in its various degrees represents an animal social system characterised by cooperative brood care, differentiation into castes and generational overlap. The fossil record indicates that eusociality is likely to have originated in hymenopterans and blattodeans during the Cretaceous. In this study, we present findings from surveys in Peruvian (Villa Carmen) and Ecuadorian (Rio Bigal, El Reventador) cloud forests revealing the first extant cockroach species living in complex, structured groups (n = 90-200 individuals, ˃ 20 adults). We observed and described behaviours that suggest the existence of cooperative care, nest guarding, nest chamber preparation within hardwood Casearia sp. (Salicaceae) and bamboo (Bambusoideae), multiple overlapping generations ('different stages of' instars), colony translocation, possibly a sole reproductive female (1.25 times larger white 'queen', but no potential 'king' observed), and morphologically diversified immature stages. In order to define the lineage where this type of sociality originated and occurs, the forms of Melyroidea magnifica Shelford, 1912, M. ecuadoriana sp. n., M. mimetica Shelford, 1912 and an undescribed species from Peru are also described in a separate section of this study. Blattoid morphological characteristics such as typical styli suggest categorisation within distinct Oulopterygidae (Rehn, 1951), outside Corydiidae Saussure 1864. Transitional advanced sociality or semisociality in related Aclavoidea socialis gen. et sp. n. is documented in a rotting stump (n = 80 individuals, few adults). Close phylogenetic relation between the genera, conserved morphology of numerous characters and their diverse feeding strategies generally lacking specialisation suggests a rather recent origin of a social way of life in this group. Eusociality in invertebrates and vertebrates can thus originate in various phylogenetical and ecological trajectories including predation, parasitism, care for herbs and the new one, documented through diet shift from detritivory to fungivory and algaevory. Interdisciplinary approaches reveal the low degree of knowledge of rainforest ecosystems, with fundamental groups remaining still systematically and also behaviourally undescribed.

Living cockroach genus Anaplecta discovered in Chiapas amber (Blattaria: Ectobiidae: Anaplecta vega sp.n.)

Cenozoic cockroaches are recent and with two indigenous exceptions, based on their fragmentary preservation state, they cannot be discriminated formally from representatives of living genera. Anaplecta vega sp.n. –the second described cockroach from Miocene (23 Ma) Simojovel amber (Mexico: Chiapas: Los Pocitos) is characterized by a slender, under 5 mm long body, prolonged mouthparts bearing long maxillary palps with a distinct flattened triangular terminal palpomere, large eyes and long slender legs with distinctly long tibial spines. Some leg and palpal segments differ in dimensions on the left and right sides of the body, indicating (sum of length of left maxillary palpomeres 65% longer than right; right cercus 13% longer than left cercus) dextro-sinistral asymmetry. The asymmetrically monstrous left palp is unique and has no equivalent. In concordance with most Cenozoic species, the present cockroach does not show any significantly primitive characters such as a transverse pronotum characteristic for stem Ectobiidae. The genus is cosmopolitan and 10 species live also in Mexico, including Chiapas, today. Except for indigenous taxa and those characteristic for America, this is the first Cenozoic American cockroach taxon representing a living cosmopolitan genus, in contrast with representaties of Supella Shelford, 1911 from the same amber source that are now extinct in the Americas.