Rearing Stink Bug Nymphs to Adulthood

While we can recognize the nymphal stages of a few of our more commonly encountered or economically important stink bugs, there just isn't nearly as much attention paid to the nymphal stages, so lots of nymphs go unidentified. The best way to determine the species for any nymph involves photographing that nymph once it has finished out its development and molted to adulthood. This little post will function as a sort of guide to helping people that want to accomplish that.

Disclaimer: I'm not encouraging anyone to remove wildlife from areas where wildlife is protected. Know the rules of the areas you are observing wildlife within. In some areas, you may find that rules about removing insect wildlife are non-existent or vague, but rules about removing plant material are often much more concrete. This can complicate rearing insects from these areas (since you'll generally want to collect host plant material).

Predatory vs Plant-Feeding Stink Bugs

One of my favorite things about stink bugs also can make them an extra challenge to rear. We have an entire subfamily of stink bugs that are predatory on other insects. Bugguide lists that we have 35 predatory species out of about 220 stink bug species in the US (about 16%) and about 6% worldwide. Obviously, rearing these to adulthood requires an entirely different set of guidelines from rearing out the phytophagous ones. Because of this, the first thing we need to do when we find a stink bug that we want to rear to adulthood is to determine whether it is a plant-feeder or an insect-feeder. The easiest way to do this is to flip it over to get a look at its mouthparts.

If you look at the second photo on this observation of a predatory 5th instar Tylospilus acutissimus nymph that I came across, you can see the robust mouthparts that are designed to hold on tightly to prey:
https://www.inaturalist.org/observations/18611661

Compare that to the last couple of photos of this phytophagous adult Euschistus inflatus where its mouthparts are simply designed for piercing plant tissue that isn't going to fight back:
https://www.inaturalist.org/observations/28891290

It's always best to try to make this determination in the field because that's going to let you know what food source to collect. But if you aren't sure, you can always flip the insect over to take a photo of the mouthparts and then tag someone like me to see if we have any information about the nymph as you start to try to rear it out.

Collecting Predatory Stink Bugs

Okay, let's say that you have found a nymph and have determined that it is in fact one of the Asopinae (predatory stink bugs). If you look closely, you will probably be able to find the food source that it is hunting. I rarely have ever found Asopine nymphs in the field that were not in close proximity to a population of potential prey. Most of these nymphs are looking for soft-bodied immature larvae of butterflies/moths or beetles. Some stink bug nymphs are happy to eat any soft-bodied insect, but there are some that are quite picky and may only be successfully reared on a few species. Since it's hard to know which insects are picky (especially if you don't know which species you are dealing with at the time), I would spend some time looking closely for the prey so that you can try to capture whatever this nymph was feeding on at the time. Whether this nymph is a generalist or a specialist, the prey that it was in the middle of hunting are probably a safe bet. I would also try to use two containers to gather material:

One container would involve the nymph, some plant material, and one or two prey items. The other would contain plant material and any additional prey that you can find. When contained, it's important to make sure the nymph only has one or two prey insects in with it at any time. I've seen instances where some prey (usually some species of caterpillars) actually turned the tables and fed on the stink bug nymph if their numbers were high enough. You may notice that the stink bug stops eating as it gets swollen and that's normal- it usually means that it is about to molt. It can also be susceptible to attack from some caterpillars during this time though. There are some species that will eat just about anything. That's why having some plant material in with the stink bug can be helpful- it gives the stink bug a way to get away from overzealous prey. You could also put a little piece of paper in the bottom of the container, folded up enough that the stink bug could crawl underneath when it wants to get away (stink bugs like to hide).

At this point, you can skip past the section on rearing phytophagous stink bugs and go to the section on setting up the container below.

Collecting Phytophagous Stink Bugs

Rearing the plant-feeding stink bugs can present some other challenges. Many stink bugs are generalist feeders and you might find them moving between plants. Others are highly specialized on specific plants. My philosophy is to let them make the choice about what they eat. I would definitely gather a good bit of plant material that you find them on. Leaves, seeds, fruits- get a variety of options for the stink bug and then you can pay attention to see what they prefer. I would also recommend capturing photos of the plant so that you can record host plant information and know what to look for if you need to return for more. With younger nymphs, I would gather extra plant material so that some can stay in the fridge to stay fresh longer.

I also like to provide most phytophagous nymphs that I collect with some sort of other food source. Fresh green beans and close relatives can be good options. If I have a species that I am not familiar with or can't find literature about nymphal rearing, I will usually set them up with a large buffet of items. This will usually include whatever I can get my hands on from this list: Green beans, snap peas, baby carrots, shelled peanuts, uncooked rice hulls. Remove food when it starts to get moldy (or before)- interestingly, a lot of times the stink bugs like older green beans even when I put new ones in for them.

The other option with plant-feeding stink bug nymphs would be to close off the plant that they are on without removing them or the plant material. You could use some sort of mesh to make a closed environment for them. I haven't tried this much (since I usually come across stink bugs in areas where I would be unable to get back to them easily) but as long as you can clear the interior of potential natural enemies before tying it off, I would think it should work fairly well.

Setting up the Rearing Container

The most important thing while rearing stink bugs in a closed container is controlling the humidity and keeping the interior fairly clean. I usually give the stink bugs a water source. Usually I use cut-up pieces of sponge. Dental wick works best, but it's quite expensive comparatively. They should be damp, but not saturated. The biggest danger is that this will cause condensation on the inside of a closed container. There are a few ways around this: You could use a container that has plenty of airflow- a screened lid or something along those lines. You could use a container that will absorb some of that moisture- if the container is derived from a paper material (think of a pint-sized ice cream container), it will take care of that issue for you. Or, if you are going the cheap route and using small, closed-off plastic tupperware type containers (like me), you can always put a piece of dry sponge in there to absorb the airborne moisture before it builds up on the inside of the container. This is especially dangerous with smaller nymphs as they can get caught in the water droplets and drown easily.

I would also recommend going through every couple of days and cleaning out the containers/transfer the insect and material to a new container. Stink bugs are messy. Since they can only take liquid food, their waste is also liquid and can quickly make a mess (especially the Asopines).

Linking the photos together

Finally, don't be shy with the camera! Take lots of shots and try to capture as much of the development as you can. Then you can post those life cycles here on iNaturalist and/or up on Bugguide where they can be valuable tools for others!

As far as posting the photos on iNaturalist goes, because each observation can only relate to a single date, the best thing I have found is to post the different stages as separate observations with links to the related observations in the description section. On ones that have been reared in captivity, I would note in the description as well this since development could be somewhat altered from insects in the wild based on temperature/climatic differences. It's a little bit easier on Bugguide where you can simply add each of the photos together and change the date for each photo.

Thanks for reading, and please feel more than free to share your own thoughts!

Questions/Answers

  1. If you find multiple instar stages, do you only take the youngest (smallest), or do you take one of each different instar to ensure they are the same species?

I would say that's kind of up to each individual. If you can be fairly sure that they are the same species, at least photograph as many stages as possible. Personally, I usually collect most of them (more chances for successful rearing if something does go wrong), but if I were to only collect one (while photographing the others), I would take the most developed. It's going to take less time to get it to adulthood, so there's less chance of something going wrong.

  1. What to do with the resulting adults:

I think everyone also has their own personal moral code. Personally, I'm working on building a Pentatomid reference collection, so I often pin and preserve the specimens that I rear out. I suppose the ideal thing would be to release insects back in the location where you found them or areas where you know that species is already present, but I would be careful about releasing insects into other areas. Ecosystems are complicated.

Posted by ameeds ameeds, August 27, 2019 16:02

Comments

Thanks, I have found many Pentatomids nymphs and have had no idea what to do with them! Now I know!

Posted by tuftedparidae about 2 years ago (Flag)

Definitely! I've reared a decent number of the ones around Cruces too, so if you find any and want to know some specifics about them, I'm happy to share! And I would think Dr. Bundy would know quite a bit about rearing out the ones around here too.

Posted by ameeds about 2 years ago (Flag)

Awesome post! Thanks so much for sharing these tips, very helpful.

Posted by kschnei about 2 years ago (Flag)

Great tutorial! Many of the steps/suggestions I never would have known. Some might be learned by trial-and-error after losing several/many subjects, but others likely would have required a better understanding of these little critters. Hardly any need for a Youtube DIY video.

Posted by natureguy about 2 years ago (Flag)

Awesome!

Posted by aispinsects about 2 years ago (Flag)

I've been contemplating rearing nymphs to adulthood and this guide is great! Thanks so much!

Posted by koaw about 2 years ago (Flag)

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