Evaniidae  

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Introduction:

Wasps in the family Evaniidae have uniquely shaped metasomas with tubular petioles and shortened, laterally compressed metasomal segments 2-8 (Fig. 1). When alive these wasps often pump their metasomas up and down, earning them the common name of ensign or hatchet wasps. Because females oviposit into cockroach egg cases (oothecae) these wasps are commonly found in houses and other buildings. They can also be seen drinking nectar on flowers or searching through leaf litter for egg cases of native cockroaches. Currently the family is divided into 31 genera, 11 of which are represented only in the fossil record, and 455 species (20 of which are fossils) (Deans 2005).

Fig. 1 Lateral habitus of Semaeomyia sp. showing the uniquely shaped metasoma, 13-segmented antenna, short and stocky body, and short, thin ovipositor.

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Rights holder/AuthorAndrew R. Deans, Tree of Life web project
Sourcehttp://tolweb.org/Evaniidae/23533

Fossil History:

Evaniids are relatively well represented in the fossil record, with species found in amber resins from the Late Cretaceous (see Fig. 4; Deans et al. 2004, Basibuyuk et al. 2002, Basibuyuk et al. 2000a, 2000b), Upper Eocene (Sawoniewicz & Kupryjanowicz, 2003, Nel et al. 2002a, Brues 1933), and Miocene (Nel et al. 2002b), as well as compression fossils from the Upper Jurassic (Zhang and Zhang, 2000), Lower Cretaceous (Rasnitsyn, 1991), and Upper Cretaceous (Rasnitsyn & Brothers 2006, Rasnitsyn 1975). These fossils suggest that the family emerged nearly 150 million years ago and has changed little since.

Fig. 4 Protoparevania lourothi Deans. From ~125 million year old Lebanese amber (Hauterivian).

Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/
Rights holder/AuthorAndrew R. Deans, Tree of Life web project
Sourcehttp://tolweb.org/Evaniidae/23533

Natural History:

Most of our knowledge about evaniid development comes from research on two cosmopolitan species, Evania appendigaster L. and Prosevania fuscipes (Illiger), which specialize on the oothecae of pestiferous Periplaneta and Blatta cockroach species (Blattidae: Blattinae). There have also been some studies on evaniids native to Europe (Brachygaster minutus (Olivier) by Brown 1973; Zeuxevania splendidula (Costa) by Genieys 1922) and North America (Hyptia spp. by Edmunds 1954, 1952a).

A female ensign wasp will typically oviposit a single egg inside an ootheca. That egg will either be inserted into a cockroach egg (Brown 1973) or between the eggs (Edmunds 1952b), depending on the species. Behavioral studies suggest that some evaniids are capable of ovipositing into oothecae carried by the female cockroach (Roth 1989), and that others will not approach the ootheca until it has been deposited (Edmunds 1952b). Records also indicate that evaniid larvae develop solitarily (i.e., one larvae per ootheca; Edmunds 1953), and that species are apparantly somewhat specialized on certain host species (Deans et al. 2006; Deans 2005). However, some researchers speculate that evaniids might actually specialize on oothecae of a certain size rather than a particular taxon (Deyrup and Atkinson 1993).

With hosts known for less than 4% of all described evaniid species, however, there are bound to be exceptional or otherwise unusual biologies.

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Rights holder/AuthorAndrew R. Deans, Tree of Life web project
Sourcehttp://tolweb.org/Evaniidae/23533

Characteristics:

Many shared, derived characters unite this group of wasps, and the family is unquestionably monophyletic. The unique metasomal morphology is the most apparent synapomorphy, but these wasps also share the following characters:

  • deeply separated jugal lobes in the fore and hind wings (Fig. 2)
  • loss of crossveins on the distal portion of the fore wings (Fig. 2). The genera vary greatly in the amount of tubular venation on the fore wing, however, and this diagnostic character may be difficult to assess (Fig. 3)
  • loss of all hind wing veins except the M,CU (and C along anterior edge of hind wing) (Fig. 2)
  • same number of antennal segments in males and females (Fig. 1; n=13, except 10 in Decevania)
  • head largely immovable and attached to the mesosoma on a short neck (Fig. 1)
  • mesosoma heavily sclerotized, sculptured, and proportionately high and short (Fig. 1)
  • ovipositor short and thin (Fig. 1)

 

Fig. 2 Evania albofacialis fore and hindwings. JL = jugal lobes, CV = reduction or loss of crossveins, M,CU = hind wing vein.

 

Fig. 3 Evaniid fore wings showing the extreme variation in venation between genera. L to R: Evaniella, Vernevania, Zeuxevania, Evaniscus, Trissevania, Brachygaster, Semaeomyia, Decevania, and Hyptia fore and hindwings.

The life history is also considered to be a synapomorphy for the family. All published rearings indicate that these wasps develop as solitary egg predators within cockroach oothecae (Dictyoptera: Blattaria).

Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/
Rights holder/AuthorAndrew R. Deans, Tree of Life web project
Sourcehttp://tolweb.org/Evaniidae/23533

Discussion of Phylogenetic Relationships:

View Evaniidae Tree

Until the early 1900s Evaniidae remained a "dumping ground" (Bradley 1908) for wasps with unusual morphological configurations, and the family was allied with or included such diverse lineages as: Aulacidae, Gasteruptiidae, Ichneumonoidea, Stephanidae, Monomachidae, Braconidae: Cenocoeliinae, Pelecinidae, Trigonalyidae, Megalyridae, and Roproniidae (Kieffer 1912, Bradley 1908). Hedicke (1939) defined the family to exclude these other lineages, and Basibuyuk et al. (2002) fine-tuned the definition of Evaniidae using characters from the extensive fossil record. Basibuyuk et al. synonymized the fossil family Cretevaniidae with Evaniidae, but their analyses could not resolve the placement of Andreneliidae (represented in the tree above as Andrenelia).

  

The relationships between extant ensign wasp genera have only recently been explored using modern phylogenetic methods (Deans et al., 2006), and more data are needed to fully resolve the evolutionary history of these wasps. The emerging picture, however, does indicate that the current generic classification is relatively robust, with the exception of two clades: 

     
  • Zeuxevania and Parevania should probably just be Zeuxevania - these genera are only separated based on the presence/absence of a single crossvein (fore wing 1RS). 
  • Szepligetella, Evaniella, and Acanthinevania may all be the same genus. Szepligetella and Acanthinevania are both Australasian, whereas Evaniella is exclusively neotropical (except one species can be found in the USA). They have exactly the same wing venation.

 

More host rearing records and phylogenetic data are required to understand the emerging pattern of host use, which seems to indicate that ensign wasps are "host" specific.

Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/
Rights holder/AuthorAndrew R. Deans, Tree of Life web project
Sourcehttp://tolweb.org/Evaniidae/23533

Statistics of barcoding coverage:

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:568
Specimens with Sequences:171
Specimens with Barcodes:127
Species:51
Species With Barcodes:48
Public Records:48
Public Species:44
Public BINs:40

Licensehttp://creativecommons.org/licenses/by/3.0/
Rights holder/AuthorSujeevan Ratnasingham, Paul D.N. Hebert, Barcode of Life Data Systems (BOLD)
Sourcehttp://www.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=80076

Barcode data:

Access Published & Released Data: Download FASTA File

Licensehttp://creativecommons.org/licenses/by/3.0/
Rights holder/AuthorSujeevan Ratnasingham, Paul D.N. Hebert, Barcode of Life Data Systems (BOLD)
Sourcehttp://www.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=80076

Locations of barcode samples:

Collection Sites: world map showing specimen collection locations for Evaniidae

Licensehttp://creativecommons.org/licenses/by/3.0/
Rights holder/AuthorSujeevan Ratnasingham, Paul D.N. Hebert, Barcode of Life Data Systems (BOLD)
Sourcehttp://www.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=80076

Evaniidae:

The Evaniidae, also known as the ensign wasps or hatchet wasps, are a family of parasitic wasps. They number around 20 extant genera containing over 400 described species, and are found all over the world except in the polar regions. The larvae of these solitary wasps feed on cockroaches, and develop inside the egg-cases (oothecae) of their hosts.[1]

Description[edit source | edit]

Evaniidae have the metasoma attached very high above the hind coxae on the propodeum, and the metasoma itself is quite small, with a long, one-segmented, tube-like petiole, and compressed laterally over most of its length (segments 2-8). The ovipositor is short and thin. When active, these wasps jerk the metasoma up and down constantly, as referenced in their common names. The mesosoma is high, short, and heavily sclerotized, with a ridged and pitted surface. The head is largely immovable and attaches to the metasoma on a short neck, with usually 13-segmented antennae that do not differ between males and females.[1]

Apomorphies of ensign wasp wings and their venation are:[1]

  • deeply separated jugal lobes in fore- and hindwings
  • loss of cross-veins on the distal forewing (though this is hard to determine in some)
  • hindwings retain only medial, cubital, and part of the costal vein; all others have been lost

Ecology[edit source | edit]

As far as is known, ensign wasp larvae are predatory on the eggs of cockroaches. But good host data are only known for a fraction of this family, about 4% as of 2008, thus more unusual life history strategies likely exist. Host specificity and coevolution with roach lineages seem to have played a significant factor in the evolution of some ensign wasp lineages. Others are less discriminating in their host choice, and will attack almost any ootheca of a particular size.[1]


Illustration of Evania appendigaster (lower right) and its pupa (upper right) as parasites of the American cockroach (Periplaneta americana)

The female wasp lays an egg inside the roach ootheca (egg case), and the wasp larva hatches quickly and consumes the roach eggs. Technically, they are thus predators, rather than parasites or parasitoids as other parasitic wasps. A single egg is laid per ootheca, into a host egg in some Evaniidae, and between the eggs in others. Some are able to oviposit even when the female cockroach still carries the fresh ootheca around, while other ensign wasps will only attack oothecae that are completed and have been dropped by the mother roach. The wasps seem to be able to determine if an ootheca is already used to host a larva, and refrain from depositing eggs in such cases; alternatively, the larvae might be cannibalic, with the first to hatch in an ootheca eating any wasp eggs subsequently deposited.[1]

Two Evaniidae species, Evania appendigaster and Prosevania fuscipes, have achieved an essentially worldwide distribution nowadays, having been introduced along with various Blattidae species of genera Blatta and Periplaneta. While they do feed on insects that are considered pests, they rarely attain population sizes sufficient to act as effective biocontrol agents. As cockroaches are typically more abundant in and around human settlements, Evaniidae are a regular sight in such habitat where many other wasps are absent, and are frequently encountered in buildings looking for prey. The adults drink nectar from flowers and neither they nor the larvae are dangerous or harmful to humans.[1]

Systematics and taxonomy[edit source | edit]

Before 1939, the Evaniidae were a "wastebin taxon" for any parasitic wasp with unusual morphology. Among these were the more apomorphic and less diverse (but about equally speciose) taxa now placed in the Aulacidae and Gasteruptiidae, which together with ensign wasps make up the superfamily Evanioidea. These were formerly a part of the paraphyletic "Parasitica", ranked as an infraorder. But the parasitic wasp lineages are not more closely related among themselves than they are related to unparasitic wasps, thus the "Parasitica" are an obsolete group.[2]

Rather, the Evanioidea seem to be close relatives of the Megalyroidea, Trigonaloidea, and particularly the Ceraphronoidea. These four superfamilies seem to make up a clade, which could be considered one of several infraorders to replace the superseded "Parasitica".[3]

Living genera[edit source | edit]

The living ensign wasp genera can be divided into one larger and four smaller groups, which might be considered subfamilies. Some genera are hard to place in these, though; they probably represent minor lineages of a more basal position. The groups, with genera sorted according to the presumed relationship, are:[1]

Basal genera

Thaumatevania group

Zeuxevania group

Evania group

Evaniella group

Hyptia group

Fossil record[edit source | edit]

Ensign wasps must have originated over 150 million years ago. Overall, they are successful organisms, existing since the time dinosaurs roamed the Earth with little change in morphology and, presumably, ecology. The fossil record, in particular from fossil amber, is quite comprehensive, with about 10 genera and twice as many species known from the Late Jurassic up to a few million years ago. The primitive Mesozoic genera Andrenelia, Botsvania, and Praevania are only tentatively identified as Evaniidae at present; the first was once separated as family Andreneliidae.[1]

Evaniidae seem to have undergone significant evolutionary radiation in the Cretaceous; these taxa were separated as Cretevaniidae, but seem to be a subfamily if anything. The main lineages of extant ensign wasps probably were well separated by the mid-Paleogene. Few Evaniidae have been found in deposits dating from the Paleogene, however, and the ancestry of the living genera consequently remains not well documented. Eoevania and Protoparevania seem to be closer to the living lineages than earlier fossils.[1]

Ensign wasp genera known only from fossils are:[1]

Footnotes[edit source | edit]

  1. ^ a b c d e f g h i j Deans (2008)
  2. ^ Deans & Jennings (2006), Deans (2008)
  3. ^ ToL (1995)
  4. ^ "1908" is lapsus in Deans (2008): see uBio (2005)

References[edit source | edit]

Licensehttp://creativecommons.org/licenses/by-sa/3.0/
Rights holder/AuthorWikipedia
Sourcehttp://en.wikipedia.org/w/index.php?title=Evaniidae&oldid=572114273

Evaniidae Latreille, 1802

Notes

Taxonomy follows Deans (2005) .

LicensePublic Domain
Rights holder/AuthorNo known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
Sourcehttp://treatment.plazi.org/id/6F6471DBE0C9B95E0D524EAD5F1EBBD0
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith