The Pireninae

The chalcidoid wasps are truly a remarkable array: tiny wonders coming in a bewildering variety of forms. For this post, I'm looking at the members of the chalcidoid subfamily Pireninae.

Macroglenes sp., copyright Charley Eiseman.

The Pireninae are currently recognised as one of the subfamilies of the Pteromalidae, a chalcidoid 'family' that is long overdue for reclassification as phylogenetic studies have agreed that it is extensively polyphyletic* (e.g. Heraty et al. 2013). The pirenines are very small wasps, about one to two millimetres in length. They've always struck me as having a fairly fly-like habitus: they lack the metallic coloration and strong sculpturing of many other pteromalids, often being uniformly black or yellow, and carry upright bristle-like setae on the head and mesosoma. Characteristic features of the Pireninae also include antennae inserted low on the face, reduced numbers of antennal segments (and hence often rather short antennae), a large clypeus that often protrudes ventrally, and a dorsally rounded mesosoma often with deeply impressed notauli (longitudinal grooves on the mesoscutum) (Bouček 1988). About ten genera are currently recognised in the subfamily. Perhaps the most remarkable is the genus Zebe, named by John La Salle in 2005 from a single female that he says, at the time, had stymied multiple hymenopterists as to what it might be for two decades. Zebe has legs with four-segmented tarsi, instead of the five-segmented tarsi of other pteromalids, and the female has a long horn extending forward from the mesoscutum and hanging over the head. As in other micro-wasps with comparable structures, this horn probably provides space for the retraction of an extraordinarily long ovipositor.

*But just in case anyone who stands to have some influence is reading, I will point out that the number of subfamilies that need to excised from the Pteromalidae could be kept to a minimum if the family is expanded to include the Ormyridae, Torymidae, Eucharitidae and Perilampidae. Bonus points that these are the families that are the hardest to distinguish from pteromalids to begin with.

Female Zebe cornutus, from Mitroiu (2011).

The life habits of most pirenines are very little known. Those whose hosts are known develop as parasites of Cecidomyiidae, gall midges, and may be found in association with the galls produced by those flies on various plants. Species of the genus Macrogelenes attack cecidomyiids associated with grasses, and some have been investigated as control agents for midges on commercial crops. So these tiny little wasps could prove themselves very valuable to humans.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Heraty, J. M., R. A. Burks, A. Cruaud, G. A. P. Gibson, J. Liljeblad, J. Munro, J.-Y. Rasplus, G. Delvare, P. Janšta, A. Gumovsky, J. Huber, J. B. Woolley, L. Krogmann, S. Heydon, A. Polaszek, S. Schmidt, D. C. Darling, M. W. Gates, J. Mottern, E. Murray, A. D. Molin, S. Triapitsyn, H. Baur, J. D. Pinto, S. van Noort, J. George & M. Yoder. 2013. A phylogenetic analysis of the megadiverse Chalcidoidea (Hymenoptera). Cladistics 29: 466–542.

La Salle, J. 2005. Zebe cornutus gen. et sp. nov., a new Pireninae (Hymenoptera: Pteromalidae) with 4-segmented tarsi and a mesoscutal horn. Acta Societatis Zoologicae Bohemoslovenicae 69: 193–197.

The Life and Times of Diaulomorpha

Diaulomorpha is a fairly typical genus of the diverse micro-wasp family Eulophidae. Like most other eulophids, members of this genus are slender with a relatively soft metasoma. The mesosoma, on the other hand, is tougher, weakly vaulted, and conspicuously reticulate dorsally. Members of the genus are known from Australasia and South America (Bouček 1988).

Body of female Diaulomorpha itea, from Bouček (1988).

Diaulomorpha species are parasitoids of insect larvae that live as miners in leaves. They are known to feed on both Lepidoptera and Hymenoptera larvae; it seems that it is not the identity of the host that attracts them but the lifestyle. They are multivoltine, that is they can go through multiple generations in the course of a year. The breeding cycle and behaviour of a Diaulomorpha species was described by Mazanec (1990) as a parasitoid of the jarrah leafminer Perthida glyphopa, a moth whose larvae attack the leaves of jarrah Eucalyptus marginata.

Mating between males and females occured after a brief courtship ritual in which the pair each extended their wings upwards and beat them up and down. Females located host larvae by running across the leaf surface and drumming the outside of prospective mines with their abdomen. They would then drill into the mine with their ovipositor, though of course the host larva would generally be trying to escape the wasp's attentions; a female might have to drill several holes before successfully piercing the caterpillar. The ovipositor would then be 'stirred' into the host to cause haemolymph and other fluids to leak out of its skin, and the wasp would feed on this fluid through the hole formed by the ovipositor. Egg laying would begin shortly after the wasp had finished feeding. Egg production was relatively slow, with only five or six eggs able to develop within the mother at a time, and the female wasp would lay through a newly created hole into the mine near the selected host. Usually only one egg would be laid in a mine but sometimes multiple eggs would be laid and the emerging larvae would share the host individual. After laying an egg, the female would tap around the laying hole with the tip of her metasoma, presumably depositing some chemical that would signal to other Diaulomorpha females that the mine had already been attacked. The host, meanwhile, would stop feeding after being stabbed with the female's ovipositor and would finally die after about a day and a half. It was around this time that the larva(e) would hatch and commence feeding on its remains.

Though healthy hosts would obviously be preferable, female Diaulomorpha were not above attacking hosts that had already died or had already been parasitised by other wasps. Such hosts were particularly likely to be attacked by young females that had not yet learnt to deal with the defensive actions of a healthy host. Deceased hosts could present a problem in that their bodily fluid pressure had been lost, and the female might have to stab them with her ovipositor several times before she had ingested enough fluid to begin laying. Pre-parasitised hosts were less of a problem as endoparasitic wasp larvae within the host would die after the Diaulomorpha's stab along with the host.

Mazarec (1990) found parasitism levels by Diaulomorpha within the host population to be low. What is more, as host populations increased the level of parasitism would plateau, so the proportion of parasitised hosts was far lower in dense host populations. This presumably resulted from the wasp's low rate of egg production: as host populations increased, the population of wasps did not keep up with it. As such, the role of Diaulomorpha in pest control is probably limited.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Mazanec, Z. 1990. The immature stages and life history of Diaulomorpha sp. (Hymenoptera: Eulophidae), a parasitoid of Perthida glyphopa Common (Lepidoptera: Incurvariidae). Journal of the Australian Entomological Society 29: 147–159.

Wasps that don't Give to a Fig

The strategies employed by flowering plants to draw in their pollinators are many and varied. Some have entered into exclusive partnerships, contriving methods by which their rewards are shared with a single animal species and hence presumably increasing the likelihood of that species visiting them. Once remarkable example of such a partnership is found among the figs. To the casual observer, fig trees might appear to never produce flowers. However, immature figs are in fact closed inflorescences called syconia with the flowers produced on the inside of the fig, never exposed to the outside world. The only way for pollinators to reach the fig flowers is through a tiny hole or ostiole at the fig's apex. This ostiole is used by the fig's pollinators, tiny female wasps of the chalcidoid family Agaonidae, who enter the fig in search of places to lay their eggs. The wasp herself does not leave the fig again after laying but her eggs and larvae develop within galls inside the fig, feeding on the tissue of the fig itself. After developing into wingless males and winged females, the next generation of fig wasps mates within the syconium; pollination of the fig tree occurs through the young females leaving the fig to find their own laying places and carrying pollen as they do so.

Female Idarnes nr flavicollis, a typical late-laying sycophagine, copyright Sergio Jansen Gonzalez.

The fig benefits by having an exclusive pollinator, the fig wasp benefits by having a ready-made nursery for its offspring. However, all that tasty fig tissue is bound to prove attractive to others who would circumvent the standard contract. Another group of chalcidoid wasps, the subfamily Sycophaginae, includes prime examples of such freeloaders. Like the true pollinating fig wasps, these non-pollinating fig wasps develop in galls within fig syconia. However, instead of entering the fig through the ostiole, most sycophagines use their ovipositor to pierce the fig's outer skin and lay from outside. In some sycophagines, the ovipositor is relatively short and thick; these species lay their eggs when the fig is only just beginning to develop. In others, the ovipositor is longer and slender, longer in fact than the rest of the wasp, and oviposition happens later when the fig has grown to a larger size. In some of these later-arriving forms, the ovipositing female lays into a gall already induced by the fig's actual pollinator (how she finds it from outside the fig, I have no idea), and as well as feeding on the gall, her larva will eventually feed on the pollinator larva. There are also some sycophagines that enter the syconium through the ostiole and oviposit internally; I haven't been able to find whether these species may function as true pollinators.

Female Sycophaga ovipositing on Ficus sur, copyright JMK.

As noted above, pollinating agaonids exhibit strong sexual dimorphism with only the females having wings, and males never escaping the host syconium. The wingless males cannot be easily recognised as belonging to the same species as the females; indeed, if one does not already know what they are, they can barely even be recognised as wasps. In sycophagines, matters are a bit more complicated. In some species, males are wingless and highly modified as in pollinating fig wasps. In others, males are winged and similar in appearance to females. And in still others, wingless and winged males are both present within a single species. I don't know what determines whether a given larva of these species develops wings or not; both forms may develop within the same syconium. It has been suggested that the presence of the two forms is related to conflicting pressures of gene flow vs speed. Winged males that can look for mates outside the parent syconium have a better chance of finding mates outside the pool of their own siblings, thus avoiding the risk of inbreeding. However, wingless males can mate with females immediately after they emerge within the syconium (if not before, as I'll explain shortly), in which case the winged males may simply find themselves too late to the party. Certainly there is a correlation between winglessness and the size of broods. Early-ovipositing species, which tend to produce smaller broods because the younger host syconium offers less space for egg-laying, are more likely to have winged males whereas males of later-ovipositing species are more likely to be wingless (Cruaud et al. 2011).

Male Apocryptophagus, copyright Centre for Biodiversity Genomics.

Males of the genera Sycophaga and Apocryptophagus (which Cruaud et al., 2011, suggested should probably be synonymised) are invariably wingless and have elongate, flattened, extensible gasters. The terminal pair of spiracles on the abdomen have the surrounding peritremes (supporting rings) extended into a pair of long filaments. In the host figs of these genera, the interior of the syconium becomes filled with liquid after being pollinated by its associated agaonids; the liquid is resorbed when the pollinators emerge. Nevertheless, there are advantages for the sycophagines in emerging before the pollinators: not only could the interior of the syconium become rather crowded, males of some agaonid species have enlarged mandibles that they may use to dispatch any interlopers. So instead of waiting for the syconial fluid to drain away, the male Sycophaga cuts a small opening slit in his gall (too narrow for the surrounding fluid to seep in) through which he partially emerges into the central cavity. The peritremal filaments are used to anchor the end of his gaster within his original gall so that he can continue to breathe from the air-pocket inside it while he stretches out in search of another gall containing a female. When he finds one, he will cut into it in the same way that he cut out of his own, then release the end of his gaster from its anchor-point and quickly slip into the gall of his intended. After a brief mating, he can repeat the process, this time using the female's gall as his air-tank (Ramírez 1996–1997). The female presumably emerges once the syconial fluid is gone.

Male Apocryptophagus emerging from a gall containing a female, from Ramírez (1996–1997).

There have been various viewpoints about the relationships of Sycophaginae to other chalcidoids. Some authors have included almost all the fig-associated wasps in the Agaonidae, whether pollinators or not. Others have restricted the Agaonidae to the true pollinators and classified non-pollinating fig wasps such as the Sycophaginae with the poorly defined family Pteromalidae. An analysis of chalcidoid relationships by Heraty et al. (2013) identified Sycophaginae as a sister group to Agaonidae sensu stricto (while placing other groups of non-pollinating fig wasps elsewhere on the tree). This might lead one to consider the possibility that the gall-making habit seen in both Sycophaginae and pollinating Agaonidae pre-dates the evolution of the wasp-fig relationship as pollinators. Perhaps the evolution of the syconium allowed figs to convert gall-makers that had previously been parasites into partners.

REFERENCES

Cruaud, A., R. Jabbour-Zahab, G. Genson, F. Kjellberg, N. Kobmoo, S. van Noort, Yang D.-R., Peng Y.-Q., R. Ubaidillah, P. E. Hanson, O. Santos-Mattos, F. H. A. Farache, R. A. S. Pereira, C. Kerdelhué & J.-Y. Rasplus. 2011. Phylogeny and evolution of life-history strategies in the Sycophaginae non-pollinating fig wasps (Hymenoptera, Chalcidoidea). BMC Evolutionary Biology 11: 178.

Ramírez, W. 1996–1997. Breathing adaptations of males in fig gall flowers (Hymenoptera: Agaonidae). Revista de Biologia Tropical 44 (3)–45 (1): 277–282.

Perilampella acaciaediscoloris: An Australian Gall Wasp

The small but incredibly diverse chalcidoid wasps are mostly known as parasitoids, their larvae attacking the eggs and young of others insects. Some, however, have chosen the vegetarian option, inserting their eggs into plant rather than animal tissue. As the larva develops, it induces the host plant to develop an often bizarre-looking growth around it that provides both shelter and food; this growth is known as a gall.

Antenna, forewing venation and dorsum of Perilampella acaciaediscoloris, from Bouček (1988).

Perilampella acaciaediscoloris is an gall-forming wasp that was first described by Froggatt in 1892 from galls that he collected on the wattle Acacia discolor, a species now regarded as a synonym of the sunshine wattle A. terminalis of south-eastern Australia. Froggatt placed his species in the genus Cynips (which is not part of the Chalcidoidea but belongs to a different micro-wasp superfamily, the Cynipoidea) but it is now placed in the chalcid subfamily Ormocerinae in the (polyphyletic) Pteromalidae. Ormocerinae are fairly generalised 'pteromalids' that are non-metallic in colour and often finely sculpted. So far as is known, ormocerines are all associated with galls in one way or another, either as gall-causers themselves or as inquilines (species that lay their eggs in the galls caused by other insects). Another ormocerine species, Trichilogaster acaciaelongifoliae, has been introduced from Australia to South Africa to help control the Sydney golden wattle Acacia longifolia.

The related ormocerine Trichilogaster acaciaelongifoliae, copyright Simon van Noort. Perilampella acaciaediscoloris most obviously differs from this species in its hairier and darker wings, and more shiny mesosoma.

The genus Perilampella differs from other ormocerines in being particularly shiny, with little clear setation. Bouček (1988) listed four Australian species in the genus, noting that P. acaciaediscoloris could be recognised by its very dark, long wings and shiny orange-yellow mesosoma. Froggatt (1892) described the galls of P. acaciaediscoloris as formed at the inception of a leaf bud or new shoot. Sometimes, they would be little more than swellings at the base of the shoot. More often, they would be oval with three irregular horns formed from aborted leaf buds. Sometimes, P. acaciaediscoloris galls would be the target of inquilines of their own that caused the gall to degrade to a shapeless mass.

REFERENCES

Bouček, Z. 1988. Australian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International.

Froggatt, W. W. 1892. Notes on Australian Cynipidae, with descriptions of several new species. Proceedings of the Linnean Society of New South Wales, second series 7: 152–156.

The Chromeurytominae: Australo-Asian Mystery Wasps

One of the most diverse groups of micro-wasps is the Chalcidoidea, a bewildering array of intricate little jewels. A number of chalcidoid taxa have been extensively studied due to their roles as parasitoids of insect pests, but there are also many groups of chalcidoids that remain little known. One such group is the Chromeurytominae.

Male Chromeurytoma sp., copyright John Heraty.

The Chromeurytominae are a small group of chalcidoids primarily known from Australia, where they are represented by two genera, fourteen species of Chromeurytoma and the monotypic Asaphoideus niger (Bouček 1988). A single species, Pitayana coccorum, has also been described from Bangladesh (Bouček & Bhuiya 1990). Characteristic features include a relatively large subrectangular pronotum (the first segment of the thorax) and an antenna with six segments between the pedicel and the clava (the club). They are more or less shiny, often with a blue or green metallic gloss, and the gaster is fairly robust and does not collapse in preserved specimens. The affinities of the Chromeurytominae have been rather uncertain and the subfamily was only established by Bouček in 1988. Chromeurytoma itself was originally described in the family Eurytomidae, with which it shares the large pronotum. Other features suggest a relationship with the family Torymidae, such as an occipital carina (a ridge around the back of the head) and prominent cerci. Currently the Chromeurytominae are treated as part of the family Pteromalidae, which is not really saying too much. As our understanding of chalcidoid phylogeny has improved in recent years, it has largely confirmed what many workers had long suspected: that once you account for the other families, the Pteromalidae is pretty much just what's left over. Nevertheless, the broad-scale analysis of chalcidoids by Heraty et al. (2013) places the Chromeurytominae within a cluster of 'pteromalid' subfamilies, closer to the type subfamily Pteromalinae than to either the Eurytomidae or Torymidae.

The chromeurytomines are a bit of a mixed bag in terms of host species, but there is the common thread that their hosts are immobile or semi-sedentary plant-feeding insects. Pitayana coccorum attacks mealybugs and other soft scales, with multiple larvae potentially developing on a single host. Asaphoideus niger attacks the citrus leaf-miner Phyllocnistis citrella. The Chromeurytoma species are associated with galls on trees such as Eucalyptus; presumably they are parasites of the insects forming the galls.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Bouček, Z., & B. A. Bhuiya. 1990. A new genus and species of Pteromalidae (Hym.) attacking mealybugs and soft scales (Hom., Coccoidea) on guava in Bangladesh. Entomologist's Monthly Magazine 126: 231–235.

Heraty, J. M., R. A. Burks, A. Cruaud, G. A. P. Gibson, J. Liljeblad, J. Munro, J.-Y. Rasplus, G. Delvare, P. Janšta, A. Gumovsky, J. Huber, J. B. Woolley, L. Krogmann, S. Heydon, A. Polaszek, S. Schmidt, D. C. Darling, M. W. Gates, J. Mottern, E. Murray, A. D. Molin, S. Triapitsyn, H. Baur, J. D. Pinto, S. van Noort, J. George & M. Yoder. 2013. A phylogenetic analysis of the megadiverse Chalcidoidea (Hymenoptera). Cladistics 29: 466–542.

Sympiesis

Female Sympiesis, copyright Lyle J. Buss.

We often imagine that parasites select their hosts largely on the basis of type: one parasite prefers caterpillars, for instance, while another prefers flies. However, sometimes what is important is not so much what type of host a parasite attacks, as where they find it. The wasp in the photo above represents Sympiesis, a sizeable genus (the Universal Chalcidoidea Database lists over 130 species) of microscopic parasitoid wasps found worldwide. The majority of Sympiesis larvae attack the larvae of Lepidoptera, but others feed on the larvae of Diptera. A few have been recorded as hyperparasitoids, attacking the larvae of other parasitic wasps. The main thing that all hosts of Sympiesis have in common, though, is that they are all found in secluded, vegetative habitats: either mining in leaves, or in retreats formed by rolling or tying leaves (sometimes boring in stems). Depending on species, Sympiesis larvae may be either ectoparasites or endoparasites: those species feeding on leaf-rolling hosts tend to be ectoparasites, while those targeting leaf-miners are endoparasites (Miller 1970).

Sympiesis is a genus of the chalcid family Eulophidae. Eulophids used to be the subject of some disagreement between myself and a colleague of mine about their ease of recognition. Eulophids are a diverse group in appearance, coming in a bewildering array of shapes and colours. However, I have always maintained that they are nevertheless readily recognisable. Whatever their appearance, eulophids seem to always a distinctive stamp of 'eulophid-ness'. They tend to be slender, relatively soft-bodied wasps, often with a flat top to the gaster. Most identification guides will tell you to look out for their four-segmented tarsi (as opposed to the five-segmented tarsi of most other chalcid wasps); eulophid tarsi are rendered even more recognisable by the point that, though they have less segments than the tarsi of other chalcids, they are not any shorter so the individual tarsal segments are all relatively long. The features distinguishing Sympiesis from other eulophid genera are, of course, finer and require fairly close examination: notably, they have relatively few dorsal setae (only four on the scutellum) (Bouček 1988). As far as I know, they are mostly metallic green in coloration.

Male Sympiesis, showing branched antennae, from here.

As with many eulophids, males of Sympiesis usually differ from females in having long branches on the antennae. However, the first species of the genus to be described, the European Sympiesis sericeicornis, is distinctive in that these antennal branches are much reduced so that the males' antennae look little different from the females' (if you look very closely, they still have just a bit of a finger on each of the middle antennal segments). This led historically to a fair bit of confusion in the recognition of Sympiesis, with many species originally being placed in segregate genera (often with tongue-twistery compound names such as Asympiesiella or Sympiesonecremnus; thank you again, Alexandre Girault). Even now, the status of Sympiesis with regard to some related smaller genera could do with further investigation; we may yet see it grow again.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Miller, C. D. 1970. The Nearctic species of Pnigalio and Sympiesis (Hymenoptera: Eulophidae). Memoirs of the Entomological Society of Canada 102 (Suppl. S68): 5–121.

A New Short-horned Elasmus

Female Elasmus curticornis Gunawardene & Taylor 2012, newly out today!

I can now officially claim not to be a one-trick pony: my first non-harvestman academic paper has just been published. The paper, "New records of Elasmus (Hymenoptera, Eulophidae) species from Barrow Island, Western Australia", written with my co-worker Nihara Gunawardene, is freely available from the Journal of Hymenoptera Research.

Elasmus is a particularly attractive genus of chalcid micro-wasps that can be immediately distinguished from most other chalcids by their massively enlarged hind coxae, which are shaped like discs, and their long wedge-shaped wings. The Elasmus species of Australia were reviewed by Riek (1967), but most of them were known only from a small number of localities, mostly on the eastern side of the continent. In the course of going through material collected on Barrow Island, Nihara and I identified several species of Elasmus that had not been previously recorded from north-west Australia, and our new paper is mostly a record of those range extensions. Also, as most of the species had never actually been illustrated before, we provided extensive colour specimen photographs.

Elasmus ero emma, from Gunawardene & Taylor (2012).

Among the specimens, though, were a couple that we couldn't quite match up with any of the species in Riek's paper. They jumped between a few different identifications, but none of them really worked. So we had to broaden our comparisons: a bit of a daunting prospect, may I note, because Elasmus has over 200 species worldwide and I wasn't really keen on the idea of checking every single one of them to see whether they were the species we had on hand. As it turned out, I needn't have worried: the unusually short antennae of this species eliminated all but a few options. And after striking out those options as well, we prepared a description of a new species: Elasmus curticornis Gunawardene & Taylor 2012.

The species name means 'short-horned', in reference to the short antennae, and also in reference to one of the other similar species, E. brevicornis, which has an extensive distribution in Eurasia. I did spend a few days pondering whether our specimens might be slightly unusual examples of E. brevicornis: the most obvious difference between the two is that E. curticornis has a much more extensive area of orange on the gaster than has E. brevicornis. Eventually, we decided to go with declaring a new species, and at least none of the reviewers shot us down. I'm still keeping an eye out for more specimens to test our identification, but it doesn't seem to be a very abundant species so far.

Elasmus auratiscutellum, photographed by yours truly.

REFERENCES

Riek, E. F. 1967. Australian Hymenoptera Chalcidoidea family Eulophidae, subfamily Elasminae. Australian Journal of Zoology 15: 145–199.

Brachymeria perflavipes and Beyond

Male of a Brachymeria species, possibly B. hammari, photographed by John Hallmén.

For the subject of today's post, the wheel-spin brought up the parasitic wasp Brachymeria perflavipes. This is a species of the family Chalcididae described by our old friend Alexander Arsene Girault in 1913 from a female specimen collected in the Dandenong Mountains in Victoria, Australia. He described it under the name of Tumidicoxa flavipes; when that genus was later synonymised by Girault in 1915, the species name was replaced by perflavipes as there was already a Brachymeria flavipes. Girault's description of this species was, thankfully, more detailed than some of his later productions, though the species was not illustrated (not an uncommon state of affairs at the time) and, to the best of my knowledge, never has been. Girault (1915) later also recorded a male from Brisbane in Queensland, collected from a lepidopteran host. And that, except for an extra host record by Bouček (1988), is pretty much the sum total of our knowledge of this species.

Brachymeria calliphorae, a parasitoid of blow fly larvae, photographed by C. Bento.

Brachymeria is a large genus of Chalcididae, with over a hundred species worldwide. The Chalcididae are, in my opinion, one of the more instantly recognisable families of Chalcidoidea, with hind femora distinctly larger than those on other legs and with a ventral row of teeth. These large hind femora enable the wasp to jump, and I can confirm from personal observation that they are adept pingers. Most Chalcididae are black with coarse punctation over most of the body, though an interesting find on one of our recent field trips was a bright electric blue chalcidid. However, despite their recognisability, a recent major molecular phylogenetic analysis of Chalcidoidea failed to recover the Chalcididae as monophyletic. Brachymeria is distinguished from other chalcidid genera by features such as a short petiole, short postmarginal vein (but even shorter stigmal vein), distinct malar suture, and hind tibia with a distinct apical spine (Bouček 1988). Attempts have been made to subdivide Brachymeria into subgenera but, as we saw with Ormyrus, proposed subgeneric divisions have been based on species found within a restricted biogeographic area (e.g. Burks 1960; Bouček 1988) and a broad worldwide survey of Brachymeria still hasn't been conducted.

Brachymeria ovata on pupa of crow butterfly Euploea core, from Brisbane Insects.

Most Brachymeria species (including B. perflavipes) are parasitoids of lepidopteran pupae, but some attack dipteran larvae or pupae (more on that in a moment). Though more than one egg may be laid within a single pupa, Dowden (1935) found that in the case of B. intermedia, a parasitoid of the gypsy moth Lymantria dispar, only one wasp would develop to maturity in a single host. Indications are that the wasp larvae themselves kill any would-be competitors within the host: the mandibles of the larva are strongly sclerotised even in the first instar, and Dowden found that dead larvae dissected out from a host invariably bore signs of injury from the mandibles. Larvae dissected out from a host and placed together would quickly attack each other.

Diagram of distinguishing characters of Brachymeria intermedia vs B. compsilurae, from Dowden (1935).

Brachymeria species also include a good example of the potential importance of reliable taxonomic identifications. The aforementioned B. intermedia has been the subject of deliberate introductions outside its native range in attempts to control its host, the gypsy moth (or, more accurately, one of its wide range of hosts). Another Brachymeria species, B. compsilurae, closely resembles B. intermedia and also appears to lay its eggs in gypsy moths. However, the target of B. compsilurae is not the gypsy moth itself, but the larvae of tachinid flies that are parasitising the moth and are themselves used in its control. Programs to introduce B. intermedia to New England had to be careful to eliminate B. compsilurae (Burks 1960), whose release would have the opposite effect of that intended.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Burks, B. D. 1960. A Revision of the genus Brachymeria Westwood in America north of Mexico (Hymenoptera: Chalcididae). Transactions of the American Entomological Society 86 (3): 225-273.

Dowden, P. B. 1935. Brachymeria intermedia (Nees), a primary parasite, and B. compsilurae (Cwfd.), a secondary parasite, of the gypsy moth. Journal of Agricultural Research 50 (6): 495-523.

Girault, A. A. 1913. On several new genera and species of Australian Hymenoptera Chalcidoidea. Canadian Entomologist 45: 101-106.

Girault, A. A. 1915. Australian Hymenoptera Chalcidoidea—XIV. The family Chalcididae with descriptions of new genera and species. Memoirs of the Queensland Museum 4: 314-365.

Munro, J. B., J. M. Heraty, R. A. Burks, D. Hawks, J. Mottern, A. Cruaud, J.-Y. Rasplus & P. Jansta. 2011. A molecular phylogeny of the Chalcidoidea (Hymenoptera). PLoS One 6 (11): e27023. doi:10.1371/journal.pone.0027023.

Ormyrids: Attacking the Gall

Female of Ormyrus nitidulus, photographed by Penny Metal.

Everyone knows about God's supposed inordinate fondness for beetles, but it is my opinion that the true poster children for insect diversity should be the wasps. Wasps, admittedly, do not have as many described species as beetles (there are some who suspect that the actual number of species of wasp may eventually be higher, but that remains in the realm of the hypothetical). However, many species of beetle are very difficult to distinguish except by skilled specialists, being otherwise small, brown, and conservative. Wasps, on the other hand, come in a kaleidoscopic array of colours and shapes, such that even a novice may look at an array of wasps (see the top of this post, for instance) and be immediately struck by the disparity.

An unnamed species of Ormyrus, photographed by Simon van Noort.

The Chalcidoidea, commonly referred to as chalcids, are one of the largest subgroups of wasps, a clade of mostly small (often minute), mostly parasitoid wasps (some have larvae that feed on plants). Members of the Ormyridae, one of the commonly recognised families of chalcids, are generally about two to three millimetres long. Ormyrids are distinguished from other chalcids by their robust body form, with a strongly sclerotised gaster* (ormyrids and perilampids tend to look like steroid-abusing pteromalids). The segments of the gaster are usually ornamented by rows of coarse foveae (pits) that give it a distinctive rough appearance, though in some species these foveae are less obvious or are replaced by longitudinal ribs (Bouček 1988). Ormyrids are often recorded in association with plant galls, but are not gall-formers themselves: rather, they are parasites of the insect larvae that formed the galls (usually flies or other wasps). Some ormyrids are associated with figs and parasites of fig wasps.

*Wasp researchers generally refer to the sections of the body behind the head by terms such as 'mesosoma' and 'gaster' (or metasoma), rather than 'thorax' and 'abdomen'. This is because the section of the body that is the first segment of the abdomen in other insects has become the last segment of the mesosoma in Hymenoptera.

A female of Ormyrus on a knopper gall (a type of gall that develops when a developing acorn of the pedunculate oak Quercus robur is parasitised by the cynipid wasp Andricus quercuscalicis), photographed by Tristram Brelstaff.

There are about 125 known species of ormyrid (making this a quite small family by chalcid standards) according to the Universal Chalcidoidea Database (an absolutely wonderful resource). However, there isn't yet a really good classification system within the family. Ormyrids vary to a fair degree, particularly in the form of the antennae or the ornamentation of the gaster, but most authors have placed almost all species within the single genus Ormyrus. Attempts to subdivide this diverse group (for instance, that of Doğanlar, 1991, who recognised four genera of ormyrids with three subgenera within Cyrtosoma) have suffered from not considering the full range of ormyrid diversity. Some of the Australian forms referred to by Bouček (1988), for instance, may not be placeable in Doğanlar's system. Until an appropriately large-scale review is conducted, most authors will probably continue to recognise an all-purpose Ormyrus.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Doğanlar, M. 1991. Systematic positions of some taxa in Ormyridae and descriptions of a new species of Ormyrus from Turkey and a new genus in the family (Hymenoptera, Chalcidoidea). Türkiye Entomoloji Dergisi 15 (1): 1-13.

Taxon of the Week: To Give Lovecraft Nightmares

After last week's fairly nominal effort at Taxon of the Week, I'm happy to report that the ecology labs are over and done with*, and I can present you with something a little more this week. Many of you will probably be aware of the existence of parasitoid** wasps - Hymenoptera that lay their eggs inside insects and other animals so that when the larvae hatch out they can devour the unfortunate host from the inside out (in some situations, you can't help but say "devour"). The most well-known examples of parasitoid wasps are the large ichneumons***, but I'll be dealing today with a different group - the micro-wasps of the Proctotrupomorpha.

*So I can stop explaining to students that their chances of having actually found a dragonfly in a pitfall trap are fairly minimal.

**Not a typo. Technically speaking, "parasitism" implies that the parasite feeds off the host without (ideally) actually killing it. "Parasitoid" Hymenoptera are referred to as such because the growth of the larva almost invariably results in the death of the host. As such, they are better described as internal predators rather than parasites. All the same, I apologise in advance for when I'm going to inevitably slip back into referring to them as parasites later on.

***Not to be confused with the mongooses also known as ichneumons. The two are easily distinguished - mongooses are much harder to fit into a collection vial.



Proctotrupomorphs are a spectacularly diverse group. The image at the top of the post from Natural History Museum shows an array of examples from only one of the component superfamilies, the Chalcidoidea. Proctotrupomorphs also include the Proctotrupoidea, Platygastroidea and Cynipoidea. Most are exceedingly small - according to the website just linked, the smallest chalcidoid (also the world's smallest insect) reaches a maximum adult size of 0.11mm. There are proctotrupomorphs with wings, there are ones without. There are species with relatively enormous 'horns' arising from the front of the abdomen that allow space for ovipositors considerably longer than the remainder of the insect (as shown above in an image from here). Most emerge from eggs or juveniles of other arthropods, but some have taken to living in galls or pollinating figs. Some are even parasitoids of other parasitic wasps. And a few are even aquatic.



A number of proctotrupomorphs exhibit what is called polyembryony. A single egg is laid within a host which then divides into a number of larvae - up to two thousand in Copidosoma floridanum. The latter species also has a remarkable characteristic in that some of the polyembryonically produced individuals, the precocious larvae, develop enlarged mandibles and seek out and destroy other larvae of the same species but from different eggs (Zhurov et al., 2004). These precocious larvae never mature and die along with the host, leaving their identical siblings (the reproductives) to emerge as adults. In another species, Encarsia formosa (shown above in a picture from Cornell University), the gift from one larva to another is even more significant, though perhaps less willing. Most E. formosa larvae are female, and develop within greenhouse white-flies. Males are much rarer, and actually have a different host - they develop as hyperparasites of the female larvae! (Askew, 1971) As with the marine fly Pontomyia, this demonstrates the dangers potentially inherent in reading morals of human society into the biology of other organisms.



In many cases, however (particularly with egg parasites), there is often no room at the inn for more than one larva - if two larvae attempt to grow within the one host, food supplies would be exhausted before either could complete development. Therefore, most parasitic wasps have measures to prevent competition within the host. As already mentioned for Copidosoma, larvae may kill each other off within the host. There are a number of cases where development of supernumerary larvae halts terminally once one has hatched out or pupated (Askew, 1971), though the mechanisms of this termination may be unclear. Some species act to prevent supernumerary oviposition from happening at all. Trissolcus basalis (image above from SARE) is a parasite of shield bug eggs. After the female has laid within an egg, she scratches the ovipositor over the cap of the egg in a figure-eight movement to leave a mark indicating that the egg has already been parasitised. As a contrast to all this, though, Tetrastichus giffardianus is an obligate superparasite of the fruit fly Dacus cucurbitae. Larvae of T. giffardianus can only avoid encapsulation* by the host if said host has already been parasitised by another wasp, the braconid Opius fletcheri.

*Encapsulation is the formation of a hard capsule around the parasite larva by the host's natural defenses, which isolates and kills the parasite.

Finally, a number of proctotrupomorphs have abandoned parasitism to become herbivores. Fig wasps are a number of families of chalcidoids that lay their eggs within fig flowers. Fig flowers are produced entirely enclosed within an immature fig, and can only be accessed by a single small hole in the fig. The female wasp crawls within the fig and lays her eggs in the flowers. The hatching larvae feed on the inside of the fig (though ovules are deep enough to escape the depredations of the larvae) before maturing. Once mature, they mate within the fig, and the males chew an exit path for the females before expiring without dispersing. The females become covered in pollen as they escape the fig (some species apparently actively collect pollen into special pockets), which they carry to the fig they will lay in. Figweb is a website with all the information on the fig-wasp interaction you could possibly want, as well as some pretty good images.

REFERENCES

Askew, R. R. 1971. Parasitic Insects. Heinemann Educational Books: London.

Zhurov, V., T. Terzin & M. Grbić. 2004. Early blastomere determines embryo proliferation and caste fate in a polyembryonic wasp. Nature 432: 764-769.