Guest blog post by Viktor Baranov
Lacewings (Neuroptera) are mostly known for representatives such as green lacewings or antlions, which are distinguished by their appearance – large eyes and four long wings – but also by their predatory larvae, which play an important role as pest control agents in agriculture. But few non-specialists know that some lacewings can look a lot like praying mantises.
Mantis lacewings (Mantispida) are among the most charismatic, though rather poorly known representatives of the true lacewings. They look like small- to medium-sized praying mantises. Mantis lacewing are 5-47 mm long, and all of them have prominent grasping (also called raptorial) legs. This superficial resemblance is due to the convergent evolution of the shape in true mantises and mantis lacewings. Convergent evolution is a process of organisms evolving similar traits, due to their adaptation to the similar conditions – i.e. hummingbirds and sunbirds live on different continents but look very similar due to their similar lifestyle. This type of evolution has led to the similar shape of the grasping legs, which act as a couple of snap traps for unsuspecting prey.
Going back to the Cretaceous, Mantis lacewings have a long geological record. There are plenty of Mesozoic records of them and their relatives, such as thorny lacewings (Rachiberothidae) and beaded lacewings (Berothidae), totalling 105 recorded specimens. Curiously, there is a clear gap in mantis lacewings records from the Cainozoic.
Until recently, no adult mantis lacewings had been recorded from Baltic amber. In a single case, fossil parasitoid larvae of mantis lacewings were found attached to their host, a spider.
This changed last year, when a beautiful specimen of the mantis lacewing, almost 2 cm long, was brought to our attention by a private amber collector and esteemed supporter of palaeoentomology research – Jonas Damzen from Vilnus, Lithuania. The specimen was found at the Yantarny mine in Kaliningrad oblast, Russia.
By analysing the morphology of this beautiful specimen, we found out that it is closely related to the extant genus Mantispa. However, it was impossible to conclusively corroborate its affinity, because important characters such as rear wing venation and genitalia were obscured by so called “verlummung” – a white film, which covers many of the fossils in Baltic amber.
So, to deal with this uncertainty, we designated this specimen as “probable Mantispa” (Mantispa?). In our research article published in the journal Fossil Record, we gave it the name Mantispa? damzenogedanica. The specific epithet is a combination of ‘Damzen’, honouring Jonas Damzen, who found, prepared, and made the specimen available, and ‘gedanicum’, relative to one of the Latin names for Gdańsk, Poland, where the specimen is housed in the Museum of Gdańsk.
Except for being an impressive, large, imposing insect fossil of the mantis lacewing, and the first one in Baltic amber at that, M.? damzenogedanica also present an intriguing question: why are so few mantis lacewings recorded from this fossil deposit, which is among the best-studied in the world?
Baltic amber deposits were formed in the mid-to-late Eocene epoch (38-33.9 MYA) in Northern Europe. Current consensus on the climate of the area at the time stands that it was not dissimilar to the south of the North American eastern seaboard, for example the Carolinas or Florida’s Panhandle: it was warm-temperate. Such climate is in fact perfect for extant mantis lacewings, so it is logical to suggest that unsuitable climate was not the main reason for the rarity of these animals in Baltic amber.
Analysing the diversity of the shape of mantis lacewings, we found a surprising trend – since the Cretaceous, the diversity in the shape of their legs has decreased. While the shape of the raptorial legs in the Cretaceous was characterised by eclectic, amazing diversity, later mantis lacewings have a rather uniform shape of raptorial legs.
We are not sure what may have caused this decrease. We think that drastic biotic changes after the Cretaceous-Paleogene extinction event (the mass extinction that killed the dinosaurs) may have led to the environment becoming less conductive to mantis lacewings, which in turn decreased their diversity. Thus, it is likely that the rarity of mantis lacewings is simply a reflection of the decline in their diversity and abundance after the Cretaceous-Paleogene extinction.
Younger amber deposits (i.e. Dominican amber), and, of course, extant fauna display significant species diversity, but the diversity of shape never recovered after the Cretaceous. This new mantis lacewing from Baltic amber offers us a rare glimpse into a time when, in the world after dinosaurs, lacewings got a little less diverse and charismatic.
Research article: Baranov V, Pérez-de la Fuente R, Engel MS, Hammel JU, Kiesmüller C, Hörnig MK, Pazinato PG, Stahlecker C, Haug C, Haug JT (2022) The first adult mantis lacewing from Baltic amber, with an evaluation of the post-Cretaceous loss of morphological diversity of raptorial appendages in Mantispidae. Fossil Record 25(1): 11-24. https://doi.org/10.3897/fr.25.80134