Anyone that knows me knows that I love wasps. I think you should love them, too. Here I will attempt to familiarize you with the world of the non-stinging wasps known as the parasitoids. Parasitic wasps do not have true stings, as the aculeate wasps [and bees] do. These parasitoids have ovipositors, which are used to lay, or sometimes inject, eggs. While there are aculeate parasitoids, the aculeates do not have ovipositors. (The exception is the Chrysididae, the cuckoo wasps, which are aculeates which evolved their own unique ovipositors independently from the parasitoids featured in this piece.) The aculeate sting evolved from an ovipositor many millions of years ago.
|Female snakefly with ovipositor, Raphidioptera|
|A colorful male Ichneumonidae metasoma|
|Ichneumonidae antennae with many flagellomeres|
|Torymus female, Torymidae, reared from a mossy rose gall|
|Toryminae female; Torymidae, reared from a mossy rose gall|
|Gasteruption and a small solitary bee|
|Cryptinae female with a US cent coin|
IchneumonoideaSome of the most recognized and speciose of the parasitoids are the wasps in the Ichneumonoidea, the superfamily which includes the ichneumons and braconids. There are over 6,000 species described north of Mexico, and at over 100,000 worldwide. Both ichneumons and braconids utilize a diversity of hosts across many insect orders and even some arachnids in various life stages from egg to adult.
The most peculiar feature among some of the Ichneumonoidea (notably the subfamilies Campopleginae and Banchinae in the Ichneumonidae, and subfamilies Microgastrinae, Miracinae, Cheloninae, Adeliinae, Cardiochilinae, Khoikhoiinae, and Mendesellinae in the Braconidae) is the presence of polydnaviruses in their genomes. Polydnaviruses are released into the host when an ichneumonoid is ovipositing, serving to suppress the immune system of the host and thus protecting the egg. The polydnavirus then infects the developing wasp larvae. Specific polydnaviruses have coevolved with the wasps they infect, and the wasps have evolved to be dependant on the virus to protect the developing wasp larvae.
IchneumonidaeThe Ichneumonidae, or ichneumon wasps, are ecto- or endoparasitoids (external and internal parasitoids, respectively) of a wide variety of insects and arachnids (including immature or adult spiders, and egg sacs of spiders and pseudoscorpions). Their hosts are always insects which exhibit complete metamorphosis (where an insect goes through four distinct stages: egg, larvae, pupae, and adult) rather than incomplete or gradual metamorphosis.
|Fused cells in ichneumon forewings create the "horsehead" often used in determining Ichneumonidae from Braconidae. The small hairs, or setae, protect the membranes, help create lift, and demonstrate hydrophobic effects.|
IchneumoninaeThe subfamily Ichneumoninae is made up of both ecto- and endoparasitic wasps which parasitize caterpillars of both lepidopterans (mostly moths) and symphytans (sawflies). They have short ovipositors, so must find hosts that are in exposed locations such as external plant feeding caterpillars. Ichneumonine wasps are idiobionts, meaning their hosts cease or slow development after oviposition. Hosts are parasitized typically in the larval or pupal stage, but wasps always emerge from pupae. Adults occasionally eat large portions of the host bodies, sometimes killing them in the process. Adults also feed on honeydew from aphids or other sap sucking insects, and are said to eat the foliage of certain plants themselves.
|A male ichneumon (Ichneumonini tribe) which I captured in a field of drying grasses. I captured (and released) many of these individuals in the same field. It is likely they were seeking females to mate with. Male ichneumons are often colorful while females tend to be drab.|
|Captured male ichneumon (Ichneumonini tribe)|
Some ichneumon females are ready to oviposit almost immediately after mating. Adult longevity and host availability are inherently connected as statistically the longer an adult female lives the more likely she will find hosts to oviposit in. Floral hosts (i.e. dandelions) and sources of honeydew (sugary frass from sap-sucking insects such as aphids) have been demonstrated in a few economically important ichneumons to increase adult longevity thus increasing their effectiveness as biocontrol agents.
BanchinaeThe Banchinae is a fairly common group of parasitoids with 1,500 species worldwide, and 600 north of Mexico. They are diurnal endoparasitoids of various larval Lepidoptera, Coleoptera, and Hymenoptera. Along with the Campopleginae, each species harbors its own genetically unique polydnavirus.
CryptinaeThe Cryptinae is the largest family of the Ichneumonidae with over 400 genera worldwide. They are mostly ectoparasites of a range of hosts including lepidopterans, coleopterans, dipterans, and even other hymenopterans. Some are hyperparasitoids of other parasitoids in the Braconidae and other ichneumonids. Females of some species are wingless (i.e. some Gelis).
|Acroricnus stylator (tribe Cryptini; Cryptinae)|
|Acroricnus stylator (Cryptinae), an individual I caught and later released.|
BraconidaeBraconids and Ichneumonids are usually differentiated by their wing venation, but some other factors come into consideration. Braconids utilize a wide variety of hosts, including aphids, bark beetles, and caterpillars. Many species parasitize eggs of their hosts, but don't fully develop until the host reaches the larval stage. Unlike the Ichneumonidae, most braconids pupate in silk-like cocoons outside the bodies of their hosts either directly attached to the host or removed from it completely. Also unlike the ichneumonids, few braconids use hosts in the pupal stage to reach maturity, with the exception of the subfamilies Alysiinae and Opiinae.
|Microgastrinae male captured around stored honey bee boxes infested with greater wax moths|
|Silk cocoons of Microgastrinae|
EvanioideaThe Evanioidea contains three families: Aulacidae, Evaniidae, and Gasteruptiidae. The Aulacidae are parasitoids of wood boring beetles, mostly Cerambycidae, and some Xiphydriidae (Symphyta). The Evaniidae, or ensign wasps, are parasitoids of cockroach egg cases.
GasteruptiidaeThe family Gasteruptiidae have unique and easily identifiable abdomens. They are sometimes known as carrot wasps, probably a hint of the forage preferences of adult wasps seeking nectar, though they will visit other plants with small flowers that have easily accessible floral resources. For instance, I have observed them visiting flowers of onions, Allium cepa.
|Gasteruption on parsley flowers in late spring|
CynipoideaGall wasps, Cynipoidea, are a unique group of parasitoids because most feed on plant tissue. Some are gall inquilines, those that live within the galls of other Cynipoidea though don't create galls themselves. Families Figitidae and Ibaliidae are parasitoids or hyperparasitoids of other insects. Figitidae wasps are parasitoids of various Diptera, Neuroptera, or are parasitoids of various gall inducing wasps in the Cynipoidea and Chalcidoidea (i.e. Cynipidae, Eurytomidae). Some Figitidae are hyperparasitoids of Braconidae or Chalcidoidea parasitoids of Hemiptera hosts. The Ibaliidae are parasitoids of sawflies in the family Siricidae. Early Ibaliidae instar larvae are endoparasitic, but later instars emerge and eat the rest of the host from the outside. The Cynipidae is made up entirely of gall inducing wasps and gall inquilines, and nearly entirely phytophagous (feed on plant tissue).
CynipidaeThe family Cynipidae is an oddity in the world of wasps (though if you have read this far, it has probably come to light that wasps, particularly the parasitoids, are an oddity as a whole). Cynipid wasps are mostly gall forming, phytophagous (herbivorous) wasps which induce galls in which to feed on and live within during their development. Inquilines don't make galls themselves, but feed on the gall of another wasp, occasionally killing the host larvae.
|Galls on the underside of Quercus garryana leaves, likely Cynips mirabilis (the larger speckled gall) and possibly Neuroterus (the small disk-shaped galls).|
|Large conspicuous galls, like those of Andricus quercuscalifornicus, are subject to predation from birds. Many galls are at least partially hidden from plain view, or may otherwise be camouflaged in some way.|
|Cynipid galls with emerged Torymus tubicola (Torymidae). Galls are subject not only to predation, but to parasitism by other insects including other hymenopterans.|
|Mossy rose gall, Diplolepis rosae|
ChalcidoideaThe Chalcidoidea is a large and varied group of small wasps with an incredibly diverse array of lifestyles. There are well over 500,000 species described worldwide, and over 2,000 in the United States alone. Most are parasitoids of insects and arachnids, yet some are plant tissue feeders who grow up within stems, leaves, seeds, or flowers, or even make galls. Fig wasps, family Agaonidae, develop and mate entirely within figs. Some are parasitoids of pest insects (within the orders Lepidoptera, Diptera, Coleoptera, and Hemiptera) and are used for pest control purposes. At least one species, Tetramesa romana (Eurytomidae), has been released into the US to control an invasive grass, Arundo donax (Poaceae).
|Torymus tubicola, a parasitoid of cynipid wasp galls.|
|A very small pteromalid on the tip of a decking screw under high magnification|
|Minimal venation is typical of chalcidoid wasps. This is the wing of a pteromalid under magnificatipon.|
TorymidaeTorymids are small, often metallic green parasitoids (occasionally phytophagous) wasps sometimes confused with chrysidids. Most are ectoparasitoids or occasionally hyperparasitoids of gall forming hymenopterans (usually Cynipidae), dipterans (Cecidomyiidae), and scale insects (Coccoidea). Species that live in the galls of others may be inquilines, parasitoids, or both entomophagous and phytophagous by feeding on both the gall and the larvae within (similar to some Eurytomidae). Some gall inquilines don't feed on the host larvae, but kill it anyway then proceed to feed on the gall tissue. A few are seed feeders, a unique group which oviposits within developing seeds where the larvae will develop on the tissue within.
|Torymus male which emerged from a mossy rose gall, Diplolepis rosae|
|Torymus male which emerged from a mossy rose gall, Diplolepis rosae|
PteromalidaeThe pteromalid wasps are mostly ectoparasitoids of Lepidoptera, Coleoptera, and to a lesser extent Diptera and other Hymenoptera (Braconidae). Some are also endoparasitoids or hyperparasitoids, though few if any are phytophagous. Adults only live for a short time, but will feed on nectar, honeydew, or sugary plant secretions. Females require protein for egg production, and host feeding is common. Females typically feed at secretions from the oviposition site, and may even consume some of the host tissue itself. Some species have been described feeding on the eggs of scale insects, as well as serving as biocontrol agents.
|Pteromalidae reared from a greater wax moth, Galleria mellonella, under magnification|
|Pteromalid eggs on a severely weakened greater wax moth larvae|
DiaprioideaThe Diaprioidea is composed of the endoparasitoids of various Diptera, and occasionally Coleoptera or other Hymenoptera. They are small, obscure wasps, and only the most basic information is known about their biology.
DiapriidaeAt least three hundred species are found north of Mexico, with four thousand species estimated worldwide. They are parasitoids of fungus gnats and other dipterans, and often found in wooded areas with decaying vegetation (where their hosts are common).
|Diapriidae with a US quarter dollar|
ConclusionThis concludes my observations of parasitoid wasps from 2017. If there is anything I would like you to take from this it is that nature is amazing. And what can you do to protect these obscure yet fascinating creatures? Plant flowers, and try to reduce your use of pesticides. It's that simple. Take notes, photos, and hikes. Watch your porch light at night (a fun way to confuse your neighbors is by staring at your porch light for an hour ion the evening). Who knows, one of us might make some new discoveries. Enjoy your wasps!
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Microgastrinae Wasps of the Worldwww.microgastrinae.myspecies.info/
Genera Ichneumonorum Nearcticae American Entomological Institutewww.amentinst.org/GIN/
Pteromalidae UC Riversidewww.faculty.ucr.edu/~legneref/identify/pteromal.htm
Universal Chalcidoidea Database. Natural History Museumwww.nhm.ac.uk/our-science/data/chalcidoids/torymidae.html
Special thanks to John Jacob @ Old Sol Bees for letting me use his microscopes.