New mid-Cretaceous cockroaches (Blattaria: Corydiidae) from Kachin amber illuminate the diversity of bipectinate antennae.

Antennae are vital insect sensory organs, primarily used for interactions with other organisms and the detection of the environment. Bipectinate antennae have evolved independently in the insect orders Lepidoptera, Coleoptera, Hymenoptera, Diptera and Cretaceous Mecoptera, Neuroptera, Trichoptera, and Blattaria. However, among Blattaria they are extremely rare and bipectinate antennae have been known only from one mid-Cretaceous species, while pectinate antennae were documented in two mid-Cretaceous species and one extant species from China. Here we describe Pinniblatta sylvana gen. et sp. nov., P. horvathovae sp. nov. and Cupidoblatta elegans gen. et sp. nov. with bipectinate antennae, all belonging to the family Corydiidae, and discovered from northern Myanmar amber. We also reassigned the genera Ol Vršanský et Wang, 2017 and Olenoblatta Šmídová 2022 to the family Corydiidae. The presence of pectinate and bipectinate antennae in males only (in 9 specimens) is likely due to sexual selection. In addition, the antennal ultrastructure, featuring an increased number of chemoreceptors, likely trichoid sensilla on the pectinae, could have served to detect female pheromones. This discovery significantly expands the known diversity of the extremely rare bipectinate antennae among Blattaria.