Parasitoid Wasps of Southern Oregon 2017

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

Wasps are in the super diverse order Hymenoptera, which also includes bees, ants, and sawflies (including horntails). This huge, and old, lineage holds more species than there are known vertebrates in the world. The orders Hymenoptera, Coleoptera (beetles), and Raphidioptera (snakeflies), among a few other orders, are thought to have evolved from a common ancestor in the Permian period. The earliest hymenopterans, the sawflies, suborder Symphyta, first appear in the Triassic period. Most sawflies (and horntails) are phytophagous, meaning the larvae feed on plant material. The first true wasps appear in the mid-Jurassic period, and the earliest known bees in the Cretaceous along with flowering plants.

A colorful male Ichneumonidae metasoma

There are over 130,000 species of wasps and bees worldwide with new species being described each year. Parasitic wasps, more ancient and possibly more speciose than the aculeate wasps and bees, have very diverse features and characteristics not found among aculeates. These features represent the diverse behaviors and life styles of the thousands of parasitic wasps found throughout the world.

Ichneumonidae antennae with many flagellomeres

Sexual dimorphism is common among the Hymenoptera and there are many features that can be used to tell the sex of individuals. The antennae of aculeates have similar numbers of flagellomeres (antennal segments) between families and can be sexed based on the number (females have ten flagellomeres while males have eleven). Parasitoids occasionally, however, have many flagellomeres and the number differs significantly between species. Males don’t lay eggs, so individuals of species which have long ovipositors can be sexed based on the presence or absence of the ovipositor. Males, in general, are difficult to identify to species since many species resemble each other, while the females bear traits that offer the best means to identify a species.

Torymus female, Torymidae, reared from a mossy rose gall 

The ovipositor of parasitoids can be long or short, and in many cases is at least partially retractable. In the case of many the ovipositor is protected within a sheath which is usually visible at all times. Lay observers of the unenlightened kind often mistake the ovipositor sheath for a sting and demonstrate unnecessary uneasiness towards the poor creature. Long ovipositors are not adapted to penetrating human skin, nor do the wasps possess a venom that would inflict any pain worth calling mother about. Some species do have short, rigid ovipositors which could potentially poke through the skin if the wasp is handled. The best advice is to leave the wasp alone if at all possible. Even if it is not capable of stinging, your attempt to coerce it onto your face would probably stress it out, and nobody needs that.

Cryptini female

Parasitoid wasps possess venom, though unlike their eusocial aculeate cousins the venom is adapted specifically for host species. Similarly to many aculeate wasps, parasitoid venom is composed of a cocktail of proteins, peptides (including kinins, found in many wasp venoms), and many toxins (the chemistry, admittedly, is beyond my education level). Some of the wasps in the families Braconidae, Ichneumonidae, and Pteromalidae possess polydnaviruses (which evolved independently in all three cases) which serve to interfere with the hosts’ immune system. Venoms injected alongside the polydnaviruses, at least in the case of the bracoviruses (the polydnaviruses possessed by braconids), further aid the pathogen to do its job. In the case of eggs injected into the host, the venoms and polydnaviruses help ensure the survival of the wasp egg(s) and larvae.

Toryminae female; Torymidae, reared from a mossy rose gall

Parasitoid venoms exhibit other characteristics including antimicrobial and biopesticidal properties. The lethality or paralyzing effects are sometimes highly dependent on the age of the host, and in some cases highly species specific. Some venoms send the host into premature pupation which the wasp larvae may need to develop properly. Other venoms simply block neurotransmitters or neuromuscular transmission which may protect an egg being deposited to the exterior of a host. Another effect of the venom of at least some braconids is the alteration of the host hemolymph for the nutritional benefit of the wasp larvae, or in other cases causing the host to become lethargic resulting in easier oviposition or protection for the immature wasps.

Gasteruption and a small solitary bee

Many adult parasitoids visit flowers for nectar or occasionally for sugary sap or honeydew, and the presence of flowers may even extend the lives of adult wasps. Many parasitoid wasps have short tongues and so only benefit from small flowers with very exposed nectar. Flowers in the Apiaceae such as herbs including parsley or coriander as well as vegetables like celery or carrots are all great plants for parasitoid wasps and will also benefit small bees and a myriad of other small beneficial insects. The composite family, Asteraceae, also has many good species for wasps. When choosing species for parasitoid wasps, select species with many small flowers instead of few large flowers. Deep tubular flowers will not benefit short-tongued wasps, but will instead be more attractive to birds, butterflies, or large bees. Planting anything is better than nothing, and planting native plants is best. Parasitoid wasps may indirectly benefit from planting host plants for insect hosts (i.e. plants which attract aphids for aphidiine wasps).

Ichneumonidae

I've been observing wasps in close detail for the last several years. They just fascinate me. When I was a kid I loved watching the silicon-based extraterrestrial parasitoids in the Alien movies designed by the late H.R. Giger, creatures which I still find both terrifying and beautiful. We are fortunate that parasitoid wasps, which aren't too different from the parasitoid aliens in some of their lifestyles, are comparatively small and do not use our bodies as hosts. Below are many of the parasitoids I had observed in 2017 through both direct organic observation and capture. Most of the encounters were completely by chance, but by realizing that these wasps are practically everywhere and knowing what to look for, you too will begin to discover tiny aliens in your backyard, workplace, and probably everywhere else you go.

Cryptinae female with a US cent coin

Ichneumonoidea

Some 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.

Ichneumonidae

The 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.

Ichneumoninae

The 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.

Many of the ichneumons are cryptic and only known from host records, meaning a researcher collected infected insect larvae or pupae and watched what emerged from its dead or dying body. Courtship and mating among ichneumons is studied to some extent but few broad scale studies have been done, with most research focusing instead on one to few closely related species.

Captured male ichneumon (Ichneumonini tribe)

Solitary females of most hymenopterans, with the exception of honey bees, usually mate with a single male while males may mate with several females. This is partially true with ichneumons. Solitary ichneumons, that is species which lay a single egg in each host, typically mate with one or less often two males. Gregarious species, females which lay more than one egg within a host, mate with multiple males.

Ichneumonini tribe

Males of most species emerge prior to the emergence of the females, occasionally congregating near the pre-emergent females. Males of some species, such as giant ichneumons, Megarhyssa spp. (Rhyssinae), inseminate pre-emergent females by inserting their elongated abdomens into the exit burrows. Insemination of this type is usually successful, though post-emergent fertilization on the tree bark with freshly emerged females has also been observed although it is less successful.

Early spring in Corvalis, Oregon, I captured and released this ichneumon (Ichneumonini tribe) which was near the entrance of a honey bee hive. The weather was overcast, windy, and wet, and it is possible this wasp was attracted to the warmth of the colony or an associated lepidopteran host.

Male ichneumons seek females with the aid of pheromones produces by the female, or by honing into the scent of a particular host plant (such as a plant in/on which the wasps’ host insect is found). In some cases both virgin and mated females exude pheromones. When male ichneumons discover a mate, they probe the female with their antennae to orient themselves for fertilization. In the case of Pimpla turionellae (a European species), and perhaps many others, male pheromones excreted from specialized glands on the antennae aid in female receptiveness when the males probe the female antennae. This antennal probing is sometimes done throughout the duration of intercourse which can take from between 1 to 20 minutes depending on the species, though mating acts have rarely been directly observed.

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.

Banchinae

The 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.

Exetastes (Banchinae)

Exetastes is a fairly common genus found worldwide with the exception of Antarctica and Australia. They inhabit mostly unforested landscapes like chaparral and oak savannas, or sometimes in large forest clearings. Adults visit flowers frequently. I have observed Exetastes visiting Daucus (carrot) for nectar in early autumn. The individual photographed here was captured in low grasses midday on a sunny southern facing hillside.

Exetastes (Banchinae)

Exetastes (Banchinae)

Hosts for Exetastes are usually cutworms (Noctuidae). Host larvae live to initiate pupation (whether it is initiated prematurely or not is unknown) in the soil by forming a pupal case. The wasp larvae kills the host after the pupal case is constructed and pupates within it.

Cryptinae

The 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).

Cryptinae

Some cryptines are at least partially nocturnal, and drawn to lights on warm evenings. Most are comparatively small in the tribes Claseini (the smallest tribe with only two genera in South America), Hemigastrini, and Phygadeuontini while the largest tribe, Criptini, includes wasps of larger average size for the subfamily.

Cryptinae

Cryptine wasps were pretty common sights for me in the summer of 2017. I had observed many small species, perhaps the same species, in and around a large apiary. The specimen photographed above was found within empty bee equipment in storage inhabited by a few paper wasps Polistes aurifer and the nonnative P. dominula. Whether there was a true association or their proximity was merely a coincidence is left for future discovery. Most cryptines seek out hosts found in soil or in leaf litter, with the exception of the Cryptini which typically seek hosts in foliage.

Acroricnus stylator (tribe Cryptini; Cryptinae)

As previously mentioned, some cryptines use other hymenopterans as hosts. Acroricnus stylator is one such species that seeks out wasp hosts which build mud nests. This includes eumenine wasps such as Ancistrocerus and Eumenes, mud daubers like Sceliphron , and mason bees (Osmia)

Acroricnus stylator (Cryptinae), an individual I caught and later released.

Acroricnus stylator is found in both the New and Old World with various regionally specific subspecies. Adults are known to feed on flowers of the carrot and daisy families. Though they parasitize other beneficial hymenopterans, their presence would suggest healthy host populations.

Xoridinae

Xoridine wasps, such as one I discovered on a door under a porch light on a cool late spring morning, are usually hosts of wood boring larvae of beetles (Cerambycidae) and horntails (Siricidae). Some may use other hosts in the Lepidoptera or Hymenoptera, or may be facultatively hyperparasitic.

Braconidae

Braconids 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.

Meteorus (Braconidae)

Many braconids, such as Meteorus, are economically important to both farmers and gardeners since hosts of these wasps include significant crop pests such as cutworms and tomato hornworms. A few studies have demonstrated that flowering plants increased the lifespans of females, possibly translating into more caterpillars taken as hosts.

Meteorus (Braconidae)

Braconid venom, at least for some species, causes apoptosis (the natural death of cells) around the oviposition site. This could serve to protect the egg, and perhaps protect the young larvae as it begins to feed.

Microgastrinae male captured around stored honey bee boxes infested with greater wax moths

In the summer of 2017, I discovered empty honey bee boxes infested with wax moths (Galleria mellonella) and numerous small cocoons. There were also pteromalid wasps, which I now suspect to be hyperparasitoids of the braconids. The cocoons were likely from microgastrine braconids (possibly Cotesia spp., a common genus). Microgastrines are koinobiont endoparasitoids, mostly on moth larvae. Some species are gregarious, meaning females lay many eggs in a host, while others are solitary.

Silk cocoons of Microgastrinae

Evanioidea

The 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.

Gasteruptiidae

The 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

Larvae of gasteruptiid wasps are predators or predator-inquilines of other hymenopterans that nest in pithy stems or twigs of woody plants. Predator-inquilines eat the larval food in the nest rather than the larvae itself, while predatory gasteruptiids feed on the larvae itself, such is the case for Gasteruption. Either way, the host larvae dies. Gasteruptiids go through winter as prepupae, then pupate in the spring.

Cynipoidea

Gall 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).

Trichoteras tubifaciens (Cynipidae), crystalline tube gall. This is my best guess as to the identity of this group of small galls. There are very few resources citing this species, which appears to be restricted to a small distribution from Northern California to Southern Oregon.

Cynipidae

The 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).

Gall forming wasps initiate the formation of a gall when certain chemicals excreted by the wasps (or on the egg) make contact with the plant tissue, though the exact mechanism is unclear in most cases. The type of plant or tree as well as the location of the gall is very specific to the species of wasp. Most gall wasps only form galls on a select few or single species on plant or tree. Usually oaks (Quercus spp.) and other trees of the family Fagaceae, or roses (Rosa spp.) are most often used as host plants for gall formation. There are some herbaceous gall formers who favor plants in the families Asteraceae, Lamiaceae, and Papaveraceae, though their galls are less conspicuous.

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.

The gall serves two primary purposes for the wasps: as a source of food for developing larvae and to protect the immature wasp from its natural enemies. The inside of the gall is full of nutritious plant tissue, and a source of protein for the wasp larvae. The outside of the gall is often hardened to form a shell-like exterior. Sometimes the outer layers are toxic, a protective measure that keeps predators from eating the gall.

Cynipid galls with emerged Torymus tubicola (Torymidae). Galls are subject not only to predation, but to parasitism by other insects including other hymenopterans.

There are at least fourteen hundred described species of cynipid wasps in the world, 750 in around fifty genera in North America. Many have interesting sex lives. Some species are believed to be completely asexual with completely female populations. Others have strange reproductive cycles. Some bivoltine species (two generations per year) have generations which alternate between sexual and asexual (parthenogenetic), such that the sexual generation which has both male and female members will yield only females. The asexual (entirely female) generation will not mate, yet will yield both male and female offspring. Quite alien when compared to our human lives!

Mossy rose gall, Diplolepis rosae

As the specific epithet implies, Diplolepis rosae forms galls on a select few species of roses. D. rosae is a European native, accidentally introduced into the United States. Wasps lay eggs on the young leaf buds in spring as new leaves emerge. They are gregarious, and multiple larvae feed on a single gall, and they remain inside the gall throughout the winter before pupating and emerging as adults in spring. They are possibly parthenogenetic in some populations, as very few males have ever been documented. Ichneumonid and chalcidoid wasps have been known to parasitize the larvae of D. rosae.

Chalcidoidea

The 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.

The smallest wasps, and smallest insects, are in the families Mymaridae and Trichogrammatidae, both contain egg parasitoids of very small host insects: Thysanoptera (thrips) and Psocoptera (barklice). The most peculiar species, however, are those which are hyperparasitic and use other parasitoids as hosts. This can be in the form of secondary or tertiary parasitoids, or to the extreme as quaternary parasitoids. This equates to a parasitoid parasitizing a parasitoid parasitizing a parasitoid of some sort of unfortunate host. It is fathomable that such an interaction may even save the original host, but only if the secondary parasitoid parasitizes the primary parasitoid before pupation, the point at which the original host would be severely weakened by the primary parasitoid. Crystal clear, right?

A very small pteromalid on the tip of a decking screw under high magnification

Some chalcidoids are polyembrionic. Polyembriony in wasps is where a single fertilized egg produces more than one larvae, and some will even produce thousands of offspring within a single host. Copidosoma floridanum (Encyrtidae) typically produces broods exceeding 2000 larvae in a single noctunid host. Some of the siblings will be nonreproductive "soldiers" who patrol the hosts body seeking out competing parasitoid larvae and killing them. Polyembriony is not restricted to the Chalcidoidea, but is also found in a few species in the Braconidae, Platygasteridae, and Dryinidae.

Minimal venation is typical of chalcidoid wasps. This is the wing of a pteromalid under magnificatipon.

In all, chalcidoid wasps attack insects in around 340 families representing fifteen orders, as well as some arachnids (i.e. pseudoscorpions, ticks, and mites) including other hymenopterans. Mostly immature stages of hosts are parasitized, but adult hosts are sometimes utilized as well as eggs and egg sacs (including spider egg sacs, in some cases).

Torymidae

Torymids 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

I have reared, albeit unintentionally, a handful of torymids from cynipid galls of various types. Galls of Cynips mirabilis, a solitary species, have yielded a single torymid per gall. Mossy rose galls, formed by the gregarious species Diplolepis rosae, yielded several torymids of varying sizes and sexes.

Torymus male which emerged from a mossy rose gall, Diplolepis rosae

Pteromalidae

The 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

In summer of 2017 I observed and captured pteromalids roaming among greater wax moth (Galleria mellonella) larvae in stored bee boxes. The wax moths had destroyed a great amount of the stored honey bee comb, but there were also many dead moth larvae and Microgastrinae (Braconidae) cocoons. To explore further, I collected several wax moth cocoons to dissect. One contained a severely weakened moth larvae with a dozen small eggs adhered to its body. I placed the larvae in a lidded jar in a temperature controlled room to observe. In two weeks small pupae were developing on the exterior of the larvae with no cocoons of their own, suggesting they rely on the moths own pupal case to protect them. A week later there were adult pteromalids walking around within the jar.

Diaprioidea

The 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.

Diapriidae

At 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

I've observed diapriid wasps on two occasions, both at porch lights in the summer. It may only be a coincidence that their host insects are dipterans, the most numerous insects to frequent my porch lights.

Conclusion

This 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!

References

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Useful Websites

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.