Tuesday 20 August 2013

A Chalcid Wasp from the Early Cretaceous of Brazil.

Chalcid Wasps are among the most widespread and numerous of all Insects, with over 22 000 described species to date, and estimates of up to half a million species in total. Chalcids are found in almost every habitat on every continent except Antarctica, though they are often overlooked due to their small size. Most Chalcids are parasitoids, laying their eggs in other invertebrates, with the larvae devouring their hosts from the inside as they grow, though a few species mature their young in galls on plants or inside seeds. The larvae of Chalcid Wasps are known to parasitize Butterflies, Moths, Beetles, True Flies, True Bugs, Spiders and even Nematodes. They have a fossil record dating back to the Middle Jurassic.

In a forthcoming paper in the journal Cretaceous Research available online since 14 June 2013, Nathan Barling of the School of Earth and Environmental Sciences at the University of Portsmouth, Sam Heads of the Illinois Natural History Survey at the University of Illinois at Urbana-Champaign and David Martill, also of the School of Earth and Environmental Sciences at the University of Portsmouth, describe a Chalcid Wasp from the Early Cretaceous Crato Formation of Brazil.

The new wasp is named Parviformosus wohlrabeae, where 'Parviformosus' means small and beautiful and 'wohlrabeae' honours Judith Wohlrabe of the University of Portsmouth, who discovered the specimen. Parviformosus wohlrabeae is a parasitoid Wasp 3.5 mm in length excluding the ovipositor (needle-like organ used to insert the eggs into their hosts) or 5.1 mm long if the ovipositor is included, making it the smallest Wasp yet discovered from the Crato Formation.

(A) Scanning electron micrograph of holotype of Parviformosus wohlrabeae in right lateral view. Scale bar is 1 mm. (B) Scanning electron micrograph of metasoma; 'x' highlights the dorsal ‘lip’ on metasomal segment 4, 'y' highlights contamination. Scale bar is 100 μm. (C) Scanningv electron micrograph of the detached ovipositor found in residue. Scale bar is 200 μm. Barling et al. (2013).

Parviformosus wohlrabeae is assigned to the Pteromalidae, a large diverse group of parasitoid Chalcid Wasps which have not previoulsy been described from the Mesozoic, the oldest until now having been a specimen in amber from the Late Eocene of Ukraine. It is also suggested that the specimen shows affinities with the Sycophaginae (Fig Wasps) due to the structure of its ovipositor, though it is at least 50 million years older than any known fossil Fig (or Fig Pollen).

Drawing of the holotype specimen of Parviformosus wohlrabeae in right lateral view with reconstruction of head. Abbreviations: Ct., contaminant; Cx.?, possible coxa; DC., damaged cuticle; E., eye; H., head; Tro.?, possible trochanter; Fm.?, possible femur; Lb., labial palpus; Msp.?, possible mesopleuron; Mst., mesothorax; Ms1-6., metasomal segments 1e6; Mlm., marginal lobe of mesosoma; MSc., mesoscutum; Nt.?, possible notaulus; OvP., ovipositor; Ppl., propleuron; Ppm., propodeum; Prt., prothorax; Pt., petiole; Sc., scutellum; LSc.?, possible lobe of scutellum; Tg.?, possible tegula; Wat., wing articulation; Wf., wing fragments. Dashed lines indicate inferred boundaries/edges of damage. Solid lines indicate clear boundaries/edges of damage. Dark grey area highlights petiole. Light grey area highlights damaged cuticle. Scale bar is 1 mm. Barling et al. (2013).

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