Journal of Paleontology, 92(2), 2018, p. 189–195 Copyright © 2017, The Paleontological Society 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.83
A new fossil evaniid wasp from Eocene Baltic amber, with highly modified compound eyes unique within the Hymenoptera
John T. Jennings,1 David D. O’Carroll,2 Priya,1 Lars Krogmann,3 and Andrew D. Austin1*
1Australian Centre for Evolutionary Biology and Biodiversity, and School of Biological Sciences, The University of Adelaide, SA 5005, Australia ⟨
john.jennings@
adelaide.edu.au⟩; ⟨
andy.austin@
adelaide.edu.au⟩; ⟨
priya@adelaide.edu.au⟩ 2Department of Biology, University of Lund, Sölvegatan 35, S-22362 Lund, Sweden ⟨
david.ocarroll@biol.lu.se⟩ 3State Museum of Natural History Stuttgart, Entomology, Rosenstein 1, 70191 Stuttgart, Germany ⟨
lars.krogmann@
smns-bw.de⟩
Abstract.—Evaniid wasps develop as solitary egg predators within the oothecae of cockroaches. Fossil evaniids are relatively common compared with most other parasitoid Hymenoptera, undoubtedly due to their searching for host cockroaches on tree trunks and thus an increased chance of being trapped in tree resin. The genus Parevania Kieffer, 1907 is widely distributed through the Old World and is also known from a small number of rather unremarkable fossil taxa. Here we add to this extinct fauna Parevania oculiseparata Jennings, Krogmann, and Austin new species from Baltic Eocene amber, a species that has highly modified compound eyes that are unique among the Hymenoptera, and possibly among insects as a whole. Parevania oculiseparata n. sp. possesses a prominent acute ridge extending across the entire dorso-ventral elongation of the eye surface. Modifications to the regular curved surface of the eyes are extremely rare among Hymenoptera and previously were only known from two species of Inostemma Haliday, 1833 (Platygastridae s. s.) and the three known species of Isomerala Shipp, 1894 (Eucharitidae). In describing this unusual fossil evaniid species, we also analyze the optical consequences of the eye surface dis- continuity, and discuss different types of compound eye modifications that occur in other Hymenoptera and other insects.
Introduction
Ensign or hatchet wasps (family Evaniidae) are solitary pre- dators on cockroach eggs in oothecae, and are easily diagnosed by a uniquely ensign- or hatchet-shaped metasoma with a tub- ular petiole and a shortened, laterally compressed metasoma. The fauna comprises ~650 extant species in 22 extant and 13 fossil genera (Deans, 2005; Deans et al., 2013; Engel et al., 2016). This relatively rich record of fossil taxa compared with some other parasitoid Hymenoptera is undoubtedly due to their searching for host cockroaches on tree trunks, and thus an increased chance of being trapped in tree resin. The genus Parevania Kieffer, 1907 is known from 26 extant
species and one subspecies from the Old World (Deans and Huben, 2003; Deans et al., 2013), and three fossil species,P. brevis (Brues, 1933), P. producta (Brues, 1933), and P. remanea (Brues, 1933) (Nel et al., 2002; Deans, 2005). Although Bradley (1908) treated Parevania as a subgenus of Zeuxevania Kieffer, 1903, Deans and Huben (2003) suggested that the genus is distinct but similar to Evaniella Bradley, 1905. However, Deans et al. (2006) found that Parevania is not monophyletic, and suggested it should be synonymized with Zeuxevania and Papatuka Deans, 2002 although this has not been formalized. Twenty-eight evaniid species have been described from
Mesozoic (Early to Late Cretaceous) or Tertiary ambers (Eocene to Miocene) and seven species from non-amber deposits, mostly
* Corresponding author
Early to Late Cretaceous (see Jennings et al., 2012, 2013a, b; Peréz-de la Fuente et al., 2012; Engel et al., 2016). Five evaniid species are knownfromEocene Baltic amber: Evaniella eocenica (Sawoniewicz and Kupryjanowicz, 2003), Hyptia hennigi Jennings, Krogmann, and Priya, 2013b, and three species of Parevania; P. brevis, P. producta,and P. remanea (Brues, 1933; Nel et al., 2002; Deans, 2005). Unfortunately the holotypes of the latter three species were deposited in Gdansk and destroyed during WorldWar II (Nel et al., 2002). Recently, a large quantity of Eocene Baltic amber with
hymenopteran inclusions was obtained by the State Museum of Natural History, Stuttgart. Examination of this material has revealed a new species of Parevania that has the most highly modified eyes of any known member of the order, and possibly of all insects, in that the eye surface has a prominent acute ridge running across and dividing the eye into two distinct regions. Here we describe this new species, present a brief analysis of the optical consequences of the eye-surface discontinuity, and discuss the likely function of the eye ridge compared with the types of compound eye modifications that occur in other Hymenoptera and other insects.
Materials and methods
Imaging and terminology.—The amber piece containing the fossil specimen, which had previously been polished, was immersed in 50% glycerol, and images taken using a Visionary Digital BK plus imaging system with a Canon EOS 7D 18
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