15 de septiembre de 2019

A Night of Pentatomid Success Blacklighting at the Texas City Prairie Preserve with some fellow iNaturalists

I joined iNaturalist in April of 2018 and have been keeping an eye on the stink bug section since. It's been fascinating to see all of this crowd-sourced data on stink bugs from all over the US in real time and there have been a couple of spots that have really caught my eye.

Over at the Texas City Prairie Preserve, on the southwest shoreline of Galveston Bay, there has been an effort by @scottbuckel and @atjelmeland to catalog the insect life that is showing up to the lights at night. The preserve is an important project by the Nature Conservancy of Texas to preserve a critically threatened habitat. The preserve's Nature Conservancy Listing notes that while coastal prairie habitats used to span over 9 million miles of coastline between TX and LA, less than 1% of that remains today. So, this preserve is dedicated to keeping that habitat protected for the interesting plants and wildlife that utilize those sorts of niches.

As part of that effort, they have been trying to record which species are found at the preserve. Part of that effort has centered on setting up lights at night and recording the insects that show up. Just looking at the stink bug diversity, I was really intrigued as to what was going on over there. They have recorded about 16 different stink bug species, including some that I found particularly interesting.

During July, they had three records of Andrallus spinidens, a predatory stink bug that has a few historical records from Texas, but it's not clear whether or not the species is established.

They've also had consistent observations of Chlorochroa saucia, a specialist of coastal marshes that typically is seen along the Atlantic coast. There was a 1978 record of the species from Galveston, but between the efforts made to catalog the species here at the TCPP and another observation from an area along the bay a bit north of the preserve, it seems clear that the species is established in the coastal marshes of this area as well.

Anyway, my wife and I took a little trip to New Orleans, so instead of flying back, we scheduled a flight out of Houston and drove the six hours out to the Galveston area. Scott and Aaron were incredibly gracious in allowing me to come out to check the lights at the preserve with them and I was not disappointed.

I got to the preserve around 7 and we immediately found a Green Stink Bug (Chinavia hilaris) that was still on the sheet from the last night of blacklighting. It stayed in the same spot almost the entire night. These guys are common throughout most of the US and a familiar sight at porch lights for a lot of folks.

Chinavia hilaris

Once it got dark, the insects slowly started showing up. Among the first to arrive (and one of the more prevalent Pentatomids of the night) were Euschistus servus, our common brown stink bug. This species can be difficult to differentiate from another common stink bug in the same genus, Euschistus tristigmus. You can tell the difference if you flip them over though. Again, this is a common species throughout the states, though it can be a challenge to nail down the ID.

Euschistus servus

Another species that showed up early on and stayed around for a good bit of the evening was Thyanta custator accerra. Like the two previous ones, this Pentatomid has a wide range and can be found throughout the country. These guys are highly variable though and can come in a variety of colors. You can see them from bright green to tan and nearly white. Some have humeral spines and some have fairly smooth shoulders. We had a couple show up that can show off some of the variety of the species.

Thyanta custator accerra

These species were all repeats for me (but still always fun to see) but I was pretty excited when Euschistus ictericus showed up a short time later. This one is a little bit easier to tell from the other members of its genus and has these impressive humeral spines and a ridge that rides across the pronotum between them. It can be found throughout most of the Eastern US and can occasionally make it out as far west as UT. They like damp habitats, so the marshes out here were a good environment for them.

Euschistus ictericus

As things stalled at the lights for a bit, I started checking some of the vegetation nearby and found another Euschistus species that was new to me. Euschistus obscurus can be fairly easy to tell from most of its congeners based on the light bar that runs across the pronotum where the insect almost looks "worn". They're a reasonably common sight in the SE US, especially around parts of TX, but I was happy to get to see one.

Euschistus obscurus

Next to show was Piezodorus guildinii, the Red-Banded Stink Bug. These guys can make it from the SE US into NM but are especially common in the West Indies and Central/South America. This one is of some economic importance as well, as it's a major pest of soybean in Brazil. Still a new one for me though!

Piezodorus guildinii

While I was looking at the first Red-Banded Stink Bug, one of the most aesthetically-pleasing (in my opinion) members of the family showed up. The Black Stink Bug (Proxys punctulatus) is found throughout the Eastern US, as well as in CA. This is one that I had seen once during my undergrad years in Missouri, but I was glad to see it a second time. They're reasonably common, but still always fun to see.

Proxys punctulatus

The first moment of real excitement came when I checked some of the plants near the lights again and noticed a small, dusty bug hanging out on the tip of one of the plants. This one was a member of the genus Amaurochrous, which are part of the subfamily Podopinae and are affectionately referred to as the "Turtle Bugs". They are found in marshy areas and are one of the stranger groups in the Pentatomidae. At times, they've even had their group elevated to family status- they differ from most other Pentatomids in that their scutellum is elongated to the point that you can't see their wing membranes, much like the Scutellerids.

Amaurochrous sp.

As the night went on most of the rest of the bugs were repeats, or the ever-present Oebalus pugnax, the Rice Stink Bug a small Pentatomid that is common throughout the Eastern US and present down into Brazil and the West Indies. They feed on grasses, and as the name suggests can cause issues in rice fields.

Oebalus pugnax

At this point, it was about 1:30, so I was getting tired. I had stuck it out for a while hoping to see Chlorochroa saucia, Chlorochroa senilis, or Euschistus crassus but it seemed like they weren't showing up. I decided to do one last walk through for the lights before calling it a night. When I got back to the sheet, I noticed a large, elongated bug hanging out and knew it had to be Chlorochroa senilis. This one is part of the subgenus Rhytidolomia, which are all fascinating bugs with specialized habitat requirements. Like saucia, senilis is a specialist of coastal marshes and just a super cool, bizarre stink bug.

Chlorochroa senilis

The excitement from that find gave me a little bit of an adrenaline push, so I decided to stick it out for another half-hour or so. I was rewarded when Chlorochroa saucia showed up to almost the exact same spot as its congener. It's interesting to compare the two- when you look at senilis it really almost seems as though someone has just taken saucia and tugged on it until it nearly doubled in length.

Chlorochroa saucia

At this point, I was quite happy with the night and was feeling pretty lucky, so I did one more walkthrough just in case Euschistus crassus had shown up somewhere. The species has been popping up pretty frequently at the preserve and around TX at the time, so I was kind of surprised that it hadn't shown up yet. Luckily, it chose to show up right around 2:30, so I was able to snap some shots of the species (maybe my favorite of the Euschistus) and call it a night.

Euschistus crassus

In all, I counted 12 different species of stink bug. 7 of these were new for me, so that's going to be a tough night to top. A huge, huge thanks to @atjelmeland and @scottbuckel for letting me come out and for showing my wife and me around the preserve the next day (also a huge thanks to my wife for letting me drive us six hours to go look at stink bugs). What a cool little area, I'll definitely be keeping an eye on the stink bug wildlife that pops up around there and encourage other iNaturalists to keep an eye on their Project here on iNaturalist. They have some really impressive species showing up here and are putting in a lot of hard work to maintain this important piece of habitat.

Ingresado el 15 de septiembre de 2019 por ameeds ameeds | 23 observaciones | 3 comentarios | Deja un comentario

27 de agosto de 2019

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. Remove food when it starts to get moldy- 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.

2. 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.

Ingresado el 27 de agosto de 2019 por ameeds ameeds | 6 comentarios | Deja un comentario

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