Parasitoid Wasp: All You Need to Know in a Nutshell

Parasitoid wasps are an intriguing group of insects that play a crucial role in controlling pest populations. These wasps lay their eggs inside other insects, allowing their larvae to feed on the host insects as they develop. While this may seem alarming, parasitoid wasps are incredibly beneficial for the environment, as they help maintain a balance in the ecosystem and control invasive species.

These small creatures come in a wide range of sizes, typically ranging from the size of a fleck of pepper to under 1/2″ long, and can be challenging to identify without the help of an expert. Adult parasitoid wasps primarily feed on nectar, pollen, and honeydew, with some species feeding on their hosts. One notable aspect is that these wasps do not sting or bite people and do not have hives that they defend, making them harmless to humans.

Examples of parasitoid wasps’ benefits include:

  • Reducing populations of agriculturally detrimental pests
  • Controlling invasive insect species
  • Acting as natural predators, maintaining biodiversity

Understanding parasitoid wasps and their role in the ecosystem is essential for anyone interested in insect biology, ecology, or natural pest control methods.

Parasitoid Wasp Biology

Life Cycle

Parasitoid wasps have a unique life cycle. They lay their eggs inside other insects, and upon hatching, the wasp larvae feed on the host insect, eventually killing it1.

  • Eggs: Female wasps lay eggs inside host insects
  • Larvae: Feeds on the host insect
  • Pupa: Transforms into an adult wasp
  • Adults: Feed on nectar, pollen, and honeydew2

Examples of host insects include aphids, caterpillars, and wood-boring beetles3.

Sting and Ovipositor

Parasitoid wasps do not sting or bite people4. Instead, they have a specialized organ called an ovipositor, which they use to lay eggs inside the host insects.

Ectoparasitoid and Endoparasitoid

There are two main types of parasitoid wasps: ectoparasitoid and endoparasitoid.

Ectoparasitoid Endoparasitoid
Lay eggs outside the host insect’s body Lay eggs inside the host insect’s body
Larvae feed on host’s external surface Larvae feed on host from within

Examples of ectoparasitoid wasps include some Braconid and Ichneumonoid wasps5, while endoparasitoid wasps include some Aphelinidae and Braconidae3.

Parasitoid wasps are beneficial for controlling native pests and invasive species4. They belong to the order Hymenoptera, which also includes ants, bees, and other wasps. These insects play a critical role in the ecosystem and can be found in various habitats across North America.

Parasitoid Wasp Diversity

Order Hymenoptera

Parasitoid wasps belong to the order Hymenoptera, which also includes ants, bees, and sawflies. They form a large and diverse group, with over 100,000 known species. These insects play crucial roles in ecosystems, with many serving as natural enemies of agricultural pests and invasive species.

  • Common features in Hymenoptera:
    • Diverse mouthparts.
    • A well-developed ovipositor in females.
    • A “wasp waist” in some groups.

Hymenopterans can also be beneficial pollinators, helping to maintain biodiversity by visiting flowers for nectar and pollen.

Notable Families

There are several important families within the parasitoid wasps, including the Ichneumonidae and Braconidae, which fall under the superfamily Ichneumonoidea, and Chalcidoidea.


  • Largest family of parasitoid wasps.
  • Over 24,000 known species.
  • Attack a wide range of insect hosts, including caterpillars, beetles, and flies.


  • Second-largest family of parasitoid wasps.
  • Over 21,000 known species.
  • Diverse lifestyles, including endoparasitism and ectoparasitism.
  • Notable species include Trichogramma, which parasitize the eggs of various insects.


  • Superfamily of wasps with over 22,000 known species.
  • Extremely small size, ranging from 0.5 mm to 11 mm.
  • Attack various hosts, including aphids, whiteflies, and mealybugs.

Comparison of Ichneumonidae, Braconidae, and Chalcidoidea:

Feature Ichneumonidae Braconidae Chalcidoidea
Size Varies Varies 0.5 mm to 11 mm
Number of Species Over 24,000 Over 21,000 Over 22,000
Host Range Caterpillars, beetles, flies Diverse Aphids, whiteflies, mealybugs

In conclusion, parasitoid wasps contribute significantly to biological control and ecosystem stability, making them essential allies in agriculture and conservation. Their sheer diversity demonstrates their adaptability, enabling them to target a wide range of pest species.

Parasitoid Wasps as Biological Control Agents

Target Pests

Parasitoid wasps are known to help control various insect pests that can harm plants. Some common pests targeted by parasitoid wasps include:

  • Caterpillars
  • Beetles
  • Flies
  • Scale insects
  • Aphids

For example, Encarsia formosa is a species of parasitoid wasp that effectively controls whitefly populations in greenhouses.

Natural Enemies and Allies

Parasitoid wasps are not without their own natural enemies. Predators like birds, spiders, and other insects may feed on the adult wasps or their cocoons. In turn, parasitoid wasps have allies in the form of plants that provide nectar and pollen sources, which adult wasps rely on for energy.

To promote beneficial insects like parasitoid wasps, consider providing:

  • Nectar-producing plants
  • Pollen-producing plants
  • Habitat for nesting and reproducing

Parasitoid Release in Agriculture

Releasing parasitoid wasps in agriculture can help control pest populations, reducing reliance on insecticides and improving crop yields. Before releasing parasitoids, it’s essential to:

  • Identify the target pest(s)
  • Select the appropriate parasitoid species
  • Determine the best release strategy

Pros of using parasitoid wasps:

  • Selective targeting of pests
  • Minimal impact on non-target organisms
  • Natural, chemical-free pest control

Cons of using parasitoid wasps:

  • Parasitoids may be susceptible to pesticide exposure
  • Dependence on proper timing and release strategies
  • Need for consistent monitoring and assessment of pest populations
Comparison Chemical Insecticides Parasitoid Wasps
Target specificity Broad-spectrum Highly selective
Environmental impact Potential harm to non-target organisms Minimal impact on non-target organisms
Resistance Pests may develop resistance Less likely for pests to develop resistance
Cost effectiveness May require frequent applications Can result in long-term control after proper release

By understanding the habits, life cycle, and benefits of parasitoid wasps, gardeners and agricultural professionals can utilize these natural enemies for effective pest control and maintain healthier ecosystems.

Parasitoid Wasp-Ecosystem Relationship

Role in Plant Pollination

Parasitoid wasps contribute to plant pollination as adults often feed on nectar and pollen. These tiny insects visit flowers while they search for nectar, transferring pollen from one flower to another. They are particularly important in the pollination of:

  • Gardens
  • Farms

These wasps, though not as efficient as bees or butterflies, help to promote plant biodiversity.

Habitats and Niches

Parasitoid wasps occupy varied habitats, including:

  • Gardens
  • Farms
  • Forests
  • Meadows

They specialize in different niches by exploiting various host insects and arthropods, such as ladybird beetles, hoverflies, lacewings, and ground beetles. Their choice of host plays a crucial role in maintaining balance in the ecosystems that they inhabit.

Evolution and Genetic Variation

Parasitoid wasps offer a fascinating perspective on evolution and genetic variation. Insect systematics and diversity studies have found numerous species under families like:

  • Aphelinidae
  • Trichogrammatidae

These wasps show a range of behaviors, from koinobiont to ectoparasitic and idiobiont. Charles Darwin referred to the Ichneumonidae family of parasitoid wasps as a significant challenge to his theory of evolution. These wasps portray complex interactions with their hosts, which helps them adapt and evolve.

Effect on Aphelinidae Trichogrammatidae
Host Psyllids, greenhouse whitefly Lepidoptera eggs
Habitat Gardens, farms Gardens, farms
Role Biological control, pollination Biological control, pollination


  • Tiny size
  • Diverse interactions with hosts
  • Different reproductive strategies

Parasitoid wasps’ genetic variation helps improve the ecosystem’s stability by controlling host populations such as yellowjackets and aphelinids. They also contribute to the overall pollination of gardens and farms. Overall, parasitoid wasps play a unique and vital role in maintaining the delicate balance within ecosystems.


  1. Agricultural Biology | Parasitoid Wasps

  2. University of Maryland Extension | Parasitoid Wasps

  3. Agricultural Biology | Life History 2

  4. UMN Extension | Parasitoid Wasps 2

  5. University of Maryland Extension | Braconid and Ichneumonoid Wasps

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Introduced Parasitoid Wasp from New Zealand


Hi Bugman,
I found this on my spinach plant the other day, in my garden in Wellington, New Zealand. It was pretty small, just an inch or so long. After checking out your site would we be right in thinking it’s a type of Ichneumon? The ovipositor looks very short compared the similar photos on your website though. Thanks,

Hi Belinda,
Your wasp is definitely an Ichneumon, one of a very large group of wasps that parasitize other insects. It looks exactly like the Banded Caterpillar Parasite Wasp, Ichneumon promissorius, that we located on the Geocities website.

Update:  November 11, 2012
We just approved a comment that identifies this as
Glabridorsum stokesii, which according to the hortnet website:  “was introduced to New Zealand from Australia in the 1960s and 70s programme of biological control of lightbrown apple moth. This ichneumonid is now established throughout the North Island and the north of the South Island. The adult female lays an egg on the surface of the leafroller pupa and the wasp larva feeds externally before becoming an internal parasite. In addition to parasitising leafrollers, this wasp is an important natural enemy of Oriental fruit moth and occasionally attacks codling moth pupae.”  We also found this very detailed report from the Department of Zoology of the University of Wellington.

Letter 2 – Parasitic Wasp from Philippines in family Stephanidae


Subject: Redhead with white tip on tail
Location: Sabang, Palawan, Philippines
February 1, 2016 2:43 am
Hi, we saw this strange bug in remnant of tropical rainforest in Palawan, Philippines. Any ideas what it is?
Signature: Lyn and Andrew

Possibly Ichneumon from Philippines
Stephanid Wasp from Philippines

Dear Lyn and Andrew,
This really is an unusual looking insect, and though we are unable to provide you with a species identity, we can tell you it is a Parasitic Hymenopteran, possibly a member of the family Braconidae, the Braconid Wasps or the family Ichneumonidae, the Ichneumon Wasps.  We will continue to try to research its identity and perhaps we will get some assistance from our readership.  The bright red head is very distinctive, and the white tipped tail is actually the ovipositor the female uses to lay her eggs.  Parasitic Hymenopterans prey upon a vast array of insects, including butterflies, moths, cockroaches spiders, often attacking the immature stages like eggs, larvae and pupae.

Many thanks Daniel. I kept researching myself – ? gasteruptidae? Thoughts? Lyn

Hi again Lyn,
The general shape of a Carrot Wasp in the family Gasteruptidae looks very close, but we cannot find any images with such a distinctive red head.

Update:  Stephanid Wasp
We received a comment informing us that this wasp is in the family Stephanidae, and we have members of the family in our archives from North America that are called Crown of Thorns Wasps.  The submitted image looks very similar to images of the Crown Wasp,
Megischus insularis, that are posted on Nature Love You.

Letter 3 – Parasitic Hymenopteran found in Pittsburgh Restaurant


Subject: Unknown bug
Location: Pittsburgh, Pa
January 29, 2016 1:29 pm
Hi bugman,
I am a service manager for a pest management company in Pittsburgh. We have a current issue with an insect in a restaurant. It is tiny with wings and is attracted to light. They are finding them along the windows along storefront and in light fixtures on first floor. No activity in basement. No second floor. Some old barn wood is inside but it has been there for several years. It appears to have an ovipositor.
Signature: thank you, Joe Ryan

Unknown Parasitic Hymenopteran
Unknown Parasitic Hymenopteran

Dear Joe,
We are not certain we will be able to provide more than a very general identification.  This is some species of Parasitic Hymenopteran, and the prominent ovipositor is used by the female to lay eggs.  Finding them indoors leads us to believe that they are preying upon some other insect or arthropod that is living in the restaurant.  Though this insect does not present a problem, it is a sign that there is something else living in the restaurant that is providing food.  Cockroaches would be a likely food source, but this is most definitely NOT an Ensign Wasp, a species that parasitizes the oothecae or egg sacs of Cockroaches.  You can try browsing the pages of BugGuide for Parasitic Hymenopterans. 

Thanks for the reply Daniel.
Although this restaurant has had problems in the past with Oriental roaches in the basement there has not been any activity reported for a year. None of these insects were found in basement along windows. I have some samples on a monitoring trap that I have to get to our Univar rep.
thanks again.

Letter 4 – Parasitic Wasps


Subject: Is it, could it be… a “Fairy Fly” wasp?
Location: Porto, Portugal
February 27, 2014 5:52 am
Olá WTB?,
I was on the laptop the other night, even looking at WTB when I saw a tiny, tiny bug on the screen, grabbed the camera and took some photos. The bug was very accommodating, apparently quite interested in the light from the computer screen. Finally though I encourage a transfer onto a paper receipt so I could hopefully get some better pics not in a backlit. But, still the tiny bug stretched the limits of my little camera.
It would seem the bug is at least a tiny wasp, but… is it possibly a fairy fly wasp? S/he seems to have long enough antennae and be small enough (that’s my middle finger in one of the photos and I have small hands). The receipt shows numbers on the other side that only measured about 1mm so that’s the size of the little flyer too.
Still February in Porto but the bugs are not waiting.
Thanks again for all you do. 🙂
Signature: Curious Girl

Parasitic Wasp
Parasitic Wasp

Dear Curious Girl,
We are posting your photos, and we hope some eminent expert on Parasitic Hymenopterans can provide you with a conclusive identification, but that is beyond the scope of our ability.  We believe this is some type of Parasitic Wasp, and you can view a wealth of species from North America on BugGuide.   At last, we are getting some rain in Los Angeles, but the experts warn that this is not a sign that the drought has ended as the snow pack is still well below average.  This rain will doubtless result in a fabulous display of desert wildflowers in the coming weeks.

Parasitic Wasp
Parasitic Wasp
Parasitic Wasp
Parasitic Wasp

Cool Daniel.
Do you think it could be Aphidiinae Braconidae (Braconid Wasp)?
Apparently they are part of Integrated Pest Management against aphids (and they get really convoluted when they attack). Funny as I did get a picture of an aphid just outside too that day though I wasn’t trying to get that one.
Here’s a couple bonus pics (though the “bug” doesn’t look much different in them). Hope you find them cool.
Plus, even though I know it messes with your system I’m sending a couple of a different tiny wasp from London’s Hyde Park last September because it came up in my search and they are so similar plus I just realized the victim for this wasp might be on the flower too! You think? I don’t believe I knew either were there when I took the picture. I think I was just trying to get the flower and the bonus was bugs.
Very cool on finally getting some rain, and hopefully some great flowers (take pictures!). I was in Death Valley once when it rained and it seemed almost immediately a bajillion tiny, tiny flowers carpeted the desert. As you no doubt know, lack of rain has not been a problem in this part of the world (especially the UK). When I was there in March ’12 they were thinking there might be a drought, so implemented water conservation only to have the 3rd wettest summer ever (which of course I also was able to experience… ::sigh::).

Parasitic Wasp
Parasitic Wasp checking out WTB?

Hi again Curious Girl,
We couldn’t resist posting your new photo in a shameless bit of self promotion.  We are also including your London image with the same posting, discarding all efforts at “neat” categorizations.  It has been pouring all night in Los Angeles, and we are expecting the rain to stay with us for over 24 hours.  It is a perfect day to stay home by the fire, but alas, we must soon drive to “the valley” for work.  We are not looking forward to the hectic morning commute.

Tiny Wasp
Tiny Wasp from London




Letter 5 – Parasitic Wasp


Subject: What kind of bug?
Location: Humble, Texas USA
February 5, 2017 12:48 pm
Dear Bugman,
We just found this bug in our yard on a leaf. He only has one wing here, so we’re not sure if he’s a flying bug. We can’t seem to find any others like him online. Can you please help us identify it? Thank you!
Signature: The Townsend family

Parasitic Wasp

Dear Townsend Family,
This is some species of Parasitic Wasp, but we do not believe it is in the highly diverse family Ichneumonidae.  While in shape it does resemble this image on BugGuide, your individual has a red thorax and no members of the genus pictured have a similar coloration.

Parasitic Wasp


Letter 6 – Parasitic Wasp


Subject: Bug
Location: Battle Ground WA
June 28, 2017 8:19 pm
Can you please tell me what is this bug? Found in my backyard.
Signature: How ever you it

Parasitic Wasp

This is some species of parasitic wasp, and based on BugGuide images, we believe it is in the genus Megischus, a group that includes the Crown of Thorns Wasp, but according to BugGuide the range is:  “Eastern United States. (Taber reports this species occurs from ‘coast-to-coast’.) ”  Your individual has white marks on the legs and the images of the Crown of Thorns Wasp lack that feature.

Parasitic Wasp
Mr Marlos
Thank you for the information. I have never seen a bug like it. It’s tail was really long, black and white.
Jeanene Reeser
Dear Jeanene,
What you have called a “tail” is the female’s ovipositor that she uses to lay eggs.

Letter 7 – Parasitoid Wasp and Cutworm Moth host


wasp that emerged from caterpillar chrysalis
Location: San Francisco
December 4, 2010 10:19 pm
This wasp-like insect hatched out of the caterpillar we were raising at my school in San Francisco. Very exciting! Just not sure what kind of wasp it is, if it is indeed one. In the sun, the black had a bluish sheen, kind of like a raven’s feathers.
Signature: Ayesha

Parasitoid Wasp

Hi Ayesha,
We can’t wait to begin to research this Parasitoid Wasp.  We wish you could tell us more about the caterpillar.  We will begin with Ichneumons.
P.S.  In our search on BugGuide we encountered this positively gorgeous Ichneumon.  We wish someone would send us a photograph of
Trogus pennator.

Parasitoid Wasp

Well, the caterpillar was eating bean leaves. It was curled up in a cutworm shape when we found it. The chrysalid had lots of webbing around it and the other chyrsalid actually turned into a moth. I will go ahead and attach the picture of the moth to this email – I didn’t want to overload you guys with ID requests but of course am wondering about the moth as well! And maybe it will help you with the parasitoid wasp.
Glad you are as intrigued! I don’t know enough about Ichneumon wasps to go there myself!

Cutworm Moth: Host to Parasitoid Wasp

Thanks for this awesome update Ayesha,
We do enjoy this type of research and we expect it to take some time.  We have several unidentified postings from today, and we are also trying to download our own photos of a Hemipteran California Black Walnut pest.

okay, cool. I am in no rush. Just glad someone else is interested, besides me!
I just checked my old emails and it was you who identified my bilobed looper moth as well. Thank you.

Letter 8 – Ichnuemon from New Zealand


Subject: Wasp identity
Location: Napier, New Zealand
March 26, 2016 7:31 pm
Hello ‘What’s That Bug’!
I was in Napier town centre the other day and saw this beautiful wasp on a car roof. Can you enlighten me as to what type of wasp this is please?
Many thanks,
Signature: Chris Atkinson

Parasitic Hymenopteran
Parasitic Ichneumon

Dear Chris,
This is a Parasitic Hymenopteran, and our initial guess would be that it is an Ichneumon Wasp, however we cannot find a matching image on the Land Care Research site.  Those orange antennae are quite distinctive, and we hope one of our readers will be able to assist with the identification.

Hi Daniel,
Thanks so much for getting back to me with that! I enjoyed checking out the website too:-)

Karl Provides the Identity:
Hi Daniel and Chris:
Your Ichneumonid wasp is probably Eutanyacra licitatoria (Ichneumonidae). The genus is represented on the Land Care Research site, along with information, but the sample image looks like a different species. In any event, it is difficult t recognize because the images are all of desiccated pinned specimens. You can also check out the Naturewatch NZ and BoldSystems sites. Regards.  Karl

Gee thanks Karl.  At first we didn’t register that the southern in Southern Alps signified the southern hemisphere rather than southern Europe, but we realized that the site is devoted to New Zealand once we researched that Otago is a southeastern region on New Zealand’s South Island.  Images of living insects are so much nicer than images of specimens.

Letter 9 – Crown of Thorns Wasp


Subject: Is this a Giant Ichneumon?
Location: Tampa, Florida, USA
July 12, 2017 5:52 pm
I took this picture when I saw a strange bug during my lunch break today in Tampa, FL. I have never seen anything like it but Google images of giant ichneumons seem to look like it. It’s on a large column in front of the office building and is probably about four to six inches long including the very long tail.
Signature: Curiously, Paul

Crown of Thorns Wasp

Dear Paul,
Like the Giant Ichneumon, this Crown of Thorns Wasp is a parasitoid, but they are not closely related.  Here is an image from BugGuide.  According to BugGuide:  “Reported to have two morphs, previously described as subspecies: ‘one with head and pronotum ferrugineous (
M. b. bicolor) and another uniformly brown or blackish (M. b. sickmanni)’ (Stephanid home page–Alexandre Pires Aguiar)” which means your color morph was once classified as Megischus bicolor bicolor.

Hi Daniel,
Thank you for taking the time and effort to identify that bug! The Crown of Thorns Wasp is definitely what I saw. I shared the information and the link with my coworkers 🙂
Hope you have a wonderful day!

Letter 10 – Torymid might have entered home on fir tree during the holidays


Subject: Torymid infestation
Location: Michigan
January 25, 2013 1:06 pm
We started noticing these small insects in a few windows around our house. They looked much like flying ants but had an ovipositor about 2/3 the length of their body. After some research the only thing that seemed to matched their size (1-3mm) and description were torymid wasps.
The strange thing is that it’s the dead of winter here and I have no idea where these originated or keep coming from. We’ve probably seen 50-100 typically located around windows.
My thoughts are they may have come from a very warm day a few weeks ago (60 deg F). The other options would be coming in on something or from our live Christmas tree this year.
Any thoughts and ideas for getting rid of them would be appreciated. I don’t care nearly as much as my wife does. She’s not excited when outnumbered by critters.
Signature: Stephan

Probably Torymid

Hi Stephan,
We agree that this looks very much like the images of Torymids that are pictured on BugGuide.  Torymids are considered Parasitic Hymenopterans and they are classified with the Chalcid Wasps.  We did some research and we believe we might have found the source of the “invasion” and we believe it will most likely end soon.  According to the USDA Agricultural Research Service website page on Torymids:  “Torymids have a wide host range with both plant and insect eating species.”  The site also states:  “Megastigmine torymids, in the New World, are entirely phytophagous, mostly within rosaceous and coniferous seeds. The major plant genera known to host these wasps are Abies, Cedrus, Chamaecyparis, Ilex, Juniperus, Larix, Picea, Pseudotsuga, Tsuga, Amelanchier, Rosa, and Pistacia (an introduced species) (Milliron 1949, Grissell 1989).”  The first mentions genus
Abies is comprised of fir trees according to the Free Online Dictionary, and fir trees are common Christmas trees.  We believe you were correct in suspecting this Torymid invasion is related to the Christmas tree.  

Letter 11 – Aulacid Wasp: Pristaulacus fasciatus


Subject: Butterwasp??!!
Location: Southern NJ
August 10, 2017 7:53 pm
Strange black wasp with butterflylike wings found in New Jersey . Looks like it has a long ovipositor.
Couldn’t find any similar photos –Help!
Signature: Thanks-Donna

Aulacid Wasp: Pristaulacus fasciatus

Dear Donna,
This is such a gorgeous wasp, that despite the difficulty, we were not going to give up until we got you an answer.  At first we thought this must be a parasitoid Ichneumon or Braconid, but we eventually learned it was neither.  We identified your parasitoid wasp as
Pristaulacus fasciatus thanks to this BugGuide image.  Of the family Aulacidae, Bugguide notes:  “Frequently mistaken for ichneumon wasps as they often frequent dead standing trees, logs, woodpiles. Note “neck” between head and thorax and the high attachment point of the metasoma” and “endoparasitoids of the wood-boring larvae of beetles (of several families, but mostly longhorns) and Xiphydria wood wasps.”  This is a new species representing a new family on our site, so we are creating a new sub-sub-category of Aulacid Wasps just to house your submission.

Dear Daniel.
Thanks so much for your quick reply-you guys are great!!!
Very exciting that you created a new sub-sub-category for our find!!!
Daniel I forgot to ask does it has a common name?

Hi again Donna.  We have not been able to find a common name, though PBase does call it an Aulacid Wasp, but that is just a reference to the family.

Letter 12 – Parasitized Caterpillar from Mexico


Subject: identify bug
Location: cuernavaca, morelos, mexico
February 2, 2017 10:42 pm
Hello bugman,
I am a biology teacher in Mexico and my kids found this bug. I am pretty sure it will turn into a butterfly or a moth, ad would like to identify it to make a case kid my students. Please help!
Thank you
Signature: Teacher Nadine

Parasitized Caterpillar

Dear Teacher Nadine,
We are not certain if this is a Brushfooted Butterfly Caterpillar in the family Nymphalidae or an early instar Giant Silkmoth Caterpillar in the family Saturniidae, but we can tell you for certain it will not turn into either a butterfly or a moth as it has been attacked by a Parasitic Wasp that laid eggs upon it.  The eggs hatched and the larval wasps feed on the internal organs, then emerged and pupated on the Caterpillar’s body.  The wasp pupae are the white rice-like objects visible in your images.  This caterpillar will die before reaching maturity.  We will attempt to get a more definitive caterpillar identification from Keith Wolfe.

Parasitized Caterpillar

Keith Wolfe Responds
Dear Teacher Nadine and Professor Bugman,
Yes, this is an unfortunate immature saturniid, POSSIBLY in the genus Hylesia (sorry, moth caterpillars are not my forte).
Best wishes,

Letter 13 – What Parasitized the Smartweed Caterpillar???


Subject: unknown parasite of Acronicta oblinita
Location: Marsh in Salamonie Reservoir, NE Indiana
September 12, 2013 7:30 am
On Aug. 24 you helped my mother identify the Smartweed Caterpillar / Smeared Dagger Moth (Acronicta oblinita) that I found on a Rose Milkweed (Ascelpias incarnata) in a marsh. I collected another from a willow branch and brought it home. It stopped moving completely and even starting spinning a strange web. To my wife’s horror, dozens of small yellow parasites slowly emerged from its side as it was still (apparently?) alive. They all seemed to perish in the hot sun and the ants had a feast. Photo attached.
I searched Google Scholar for some clues…
I see a 1903 reference to a ”Rhogas rileyi Cress” being parasitic, mentioning the silk I saw (p. 24 here: However, I cannot find R. rileyi Cress in recent mention so I wonder if the name has been updated. I see a recent publication noting that the parasitic wasp Aleiodes rileyi Cresson often chooses A. oblinita as a host, but it did not seem to undergo the mummification described.
Signature: Adam Thada

Parasitized Smartweed Caterpillar
Parasitized Smartweed Caterpillar

Hi Adam,
We are very impressed with your research, but in our opinion, the parasites that emerged from the Smartweed Caterpillar look more like fly larvae to us, so with that in mind, we would lean more toward this being an instance of parasitization by Tachinid Fly.  We have not been able to uncover any evidence, and that is just our first impression.  Perhaps one of our readers will have better luck determining What Parasitized the Smartweed Caterpillar?

Parasitized Smartweed Caterpillar
Parasitized Smartweed Caterpillar

Comment courtesy of Erwin
Subject: What Parasitized the Smartweed Caterpillar???
December 13, 2013 5:45 am
Going through some older posts I found one submitted on Sept.13, 2013 by Adam Thada. These parasites are Braconidae for sure. Braconidae (genus Apanteles and others) are well known as parasites of Acronycta caterpillars.
Here you can see as an example larvae of Braconidae coming out of a caterpillar of Pieris sp.
(Please scroll down)
Signature: Erwin Beyer

Hi Erwin,
Your comment was written as though you provided a link by indicating to “scroll down”.  We did not get the link.

Subject: here is the link
December 13, 2013 9:04 am
Dear Daniel,
here is the required link:
Signature: Erwin Beyer

The Braconids in the link you provided look exactly like the ones submitted to us.  Thanks Erwin.

Letter 14 – Moth Caterpillars from Costa Rica, one parasitized by wasp


Subject: Caterpillars in Costa Rica
Location: Monteverde, Costa Rica
April 24, 2015 10:28 am
What are these caterpillars, what are they going to turn into, why do they clump like this, and why does one (lower right) appear to have white things on it?
Signature: Ashley from the Monteverde Institute

Nymphalidae Caterpillars
Moth Caterpillars

Dear Ashley,
We believe these Caterpillars are in the Brush Footed Butterfly family Nymphalidae, and the caterpillar in question appears to have been parasitized by a Chalcid or Braconid Wasp.  We will contact Keith Wolfe to see if he can identify the caterpillars more specifically.

Nymphalidae Caterpillar parasitized by Wasp
Moth Caterpillar parasitized by Wasp

Keith Wolfe provides a correction
Hi Daniel,
Nope, these are immature moths, the scoli (spines) being much too long for any Neotropical nymphalid.
Best wishes,

After Keith Wolfe’s correction, we are now speculating that they are relatives of Buck Moths in the subfamily Hemileucinae and we will see if Bill Oehlke can provide any information.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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15 thoughts on “Parasitoid Wasp: All You Need to Know in a Nutshell”

  1. These are Hylesia larvae (Saturniidae), there are over 100 species in the neotropics. The larvae are gregarious, often nocturnal and roost in “rafts” during the day on lower trunks, in treeholes, under loose bark and even rock crevices in their later instars. The long anterior scoli broadened at tips with bands of bright white, black or metallic blue are diagnostic. The adult female moths of some species are famous for causing vicious rashes in humans (see Carapito Itch).

  2. There is a parasite that oviposits in or near grain weevils which seems believable in a restaurant setting. I can’t remember the name though!

    • We will attempt to research that. Many of the parasitic hymenopterans are small and look quite similar, and there is not really that much detail in the provided image.

  3. I found a very similar case on the 28.01.2021, also in Cuernavaca, Morelos, Mexico. How can I upload a picture?
    Do you know the name (or genus) of the wasp?

  4. I found a very similar case on the 28.01.2021, also in Cuernavaca, Morelos, Mexico. How can I upload a picture?
    Do you know the name (or genus) of the wasp?


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