A new species of fossil Corethrella (Diptera, Corethrellidae) from mid-Cretaceous Burmese amber

Abstract

Frog-biting midges (Diptera: Corethrellidae) are hematophagous flies in which females feed on anuran blood using the mating calls produced by calling male frogs. This family is of large ecological, evolutionary and ethological interest, but its geological history is poorly known. We describe a new species of frog-biting midge (Diptera, Corethrellidae), Corethrella patula sp. nov., from mid-Cretaceous Burmese amber (ca. 99 Ma). This new species is distinct from Corethrella andersoni, known from the same deposit, differing in having more slender mid femora and a triangular bifid tarsal segment 5 without scales. These two species, however, share an apparent synapomorphy in the wing; R₂ vein diverting from R₂₊₃ at 75° angle in relation to R₃. The well-preserved male genitalia of the new species suggest C. patula and C. andersoni are a distinct, early lineage not easily placeable within either of the described subgenera of Corethrella.

Introduction

The Cretaceous was a pivotal period in the history of the Earth given that it marks the origin of the biosphere as we know it (Butler et al., 2009). Many biotic interactions, such as plant-pollinator relationships (Angiosperm plants and insects) and brood care adaptations (e.g. cockroaches, ants), emerged during this period (Anderson, 2009, Grossnickle and Polly, 2013, Wang et al., 2015b). Another set of important biotic interactions that apparently emerged in the Cretaceous were host-parasite relationships between blood-feeding flies (Diptera) and vertebrates (Martins-Neto, 2003, Borkent et al., 2013, Borkent and Grimaldi, 2004). The oldest records of true mosquitoes (Culicidae), biting midges (Ceratopogonidae), sand flies (Psychodidae: Phlebotominae) and horse flies (Tabanidae) are all of Cretaceous origin (Hennig, 1972, Martins-Neto, 2003, Borkent et al., 2013, Borkent and Grimaldi, 2004).

Another group of bloodfeeding Diptera that made its first appearance in the Cretaceous is the frog-biting midges (Diptera, Corethrellidae) (Szadziewski, 1995). This group is a small monobasic family of culicomorph Diptera represented by a single genus Corethrella Coquillett, 1902a (Borkent, 2008, Borkent and Grafe, 2012). Like many other Culicomorpha, Corethrellidae are haematophagous micropredators of vertebrate prey. Corethrellids, in particular, are specialized on feeding on frogs (McKeever, 1977, McKeever and Hartberg, 1980.; Bernal et al., 2006, Bernal et al., 2007, Grafe et al., 2008). Together with a few Culicidae species from the genera Uranotaenia Lynch Arribálzaga, 1891, Culex Linnaeus, 1758 and Mimomyia Theobald, 1903, Corethrellidae are unique among bloodsucking Diptera in locating their prey mainly using sound rather than chemical cues (McKeever, 1977, McKeever and Hartberg, 1980, Toma et al., 2005, Borkent, 2008, Bartlett-Healy et al., 2008, Bernal and de Silva, 2015, Camp et al., 2018). Being eavesdropping micropredators of frogs and vectors of trypanosome blood parasites (Johnson et al., 1993, Bernal and Pinto, 2016), frog-biting midges are an important model system in acoustic ecology and co-evolution of prey, vectors and micropredators (Bernal et al., 2006, Grafe et al., 2008, de Silva et al., 2015, Legett et al., 2018).

The genus Corethrella includes 110 species to date and has a semi-cosmopolitan distribution with the vast majority of extant species restricted to the tropics and subtropics (Borkent, 2008, Borkent, 2012, Amaral and Pinho, 2015, Wang et al., 2015a, Baranov et al., 2016, Caldart et al., 2016, Kvifte and Bernal, 2018). The current distribution and phylogenetic relationships of lineages in this family indicate that they originated in the Southwestern Pacific. Since the earliest diverging extant species of Corethrella is found in New Zealand, which is also home to one of the two earliest lineages of frogs (Duellman and Trueb, 1994; Pyron and Wiens, 2011), it has been suggested that frog-biting midges and their anuran prey share a long evolutionary history together (Borkent and Szadziewski, 1992).

Frog-biting midges probably originated around the Jurassic/Cretaceous boundary about 145 Ma (Bertone et al., 2008). The oldest record from this family is C. cretacea Szadziewski, 1995, which was found preserved in 125–129 Ma Lebanese amber (Szadziewski, 1995, Maksoud et al., 2017). Indeed, all known fossil Corethrellidae are found in amber. The absence of specimens from this family in compression fossils has been attributed to the lifestyle of the known larvae which are largely arboreal and phytotelmatic, factors that do not make them amenable to preservation in lacustrine sediments (Lukashevich, 2000). Overall, however, this family is rare in the fossil record with fewer than 20 fossil specimens known in total, many poorly preserved (Borkent, 2014, Baranov et al., 2016). Among these, nine fossil species of Corethrella have been described, two from the Cretaceous, five from the Eocene and two more from the Miocene (Szadziewski, 1995, Borkent, 2008, Baranov et al., 2016). The rarity of Corethrellidae fossils makes it difficult to investigate the early evolutionary history of this family.

In this paper, we describe a new species of Corethrellidae from mid-Cretaceous Burmese amber from Myanmar, a deposit from which a different species of frog-biting midge had been previously described (Corethrella andersoni Poinar and Szadziewski, 2007). The new species provides new data on character evolution in the early evolutionary history of Corethrellidae, in particular concerning male genitalia. Finally, we compare the new species to other known fossil frog-biting midges and discuss the origin of frog-biting midges in relation to their feeding behavior.