I came across a small population of Goldenrain Tree Bugs (Jadera haematoloma) this week cavorting beneath their namesake host in a southwest Ohio landscape. The bugs do not have a common name that's been approved by the Entomological Society of America.
They are called "goldenrain tree bugs" in reference to a favored host, the non-native goldenrain tree (Koelreuteria paniculata) which belongs to the soapberry family, Sapindaceae. The native bugs have also feed on native members of the soapberry family which earned them the common name "soapberry bugs." The common names "Jadera bugs" references the bug's genus and "red-shouldered bugs" point to a clear morphological feature.
I first saw goldenrain tree bugs in Ohio in 2012. They were unexpected because historically, the bugs were relegated to the southeastern U.S. from Florida to Texas but no farther north than the range of its various native soapberry plant hosts.
The bugs are commonly mistaken for Boxelder Bugs (Boisea trivittata). The misidentification is understandable given that both are "true bugs" meaning they belong taxonomic suborder Heteroptera within the order Hemiptera. True bugs have front wings with both membranous and hardened areas.
Boxelder and goldenrain tree bugs also belong to the same family Rhopalidae (Scentless Plant Bugs) and they share many family traits. Both bugs have the same elongated body shape and are about the same size.
Both bugs use their piercing/sucking mouthparts (beaks) to penetrate plant seeds, inject enzymes that dissolve the proteins and fats, then suck up the seed slurry. So, the bugs tend to appear in large numbers as seeds are ripening. They both can become a serious nuisance by appearing en mass around and on homes in the fall with the intention of entering to find a protected spot for the winter.
However, the bugs differ in some obvious ways that are referenced in their scientific names. The specific epithet for boxelder bugs, trivittata, is Latin for "three-striped" which references the three reddish-orange lines on the pronotum. The specific epithet, haematoloma, is Greek for "blood-fringed," and describes the deep red "shoulders" on the goldenrain tree bugs. Indeed, another common name for the bug is "red-shouldered bug."
Boxelder bugs focus most of their feeding attention on the seeds of their namesake host, Acer negundo (family Sapindaceae). Goldenrain tree bugs are most commonly found in Ohio tapping goldenrain tree seeds. I've never seen boxelder bugs on goldenrain tree or goldenrain tree bugs on boxelder. But that's only in Ohio.
However, these bugs may be found on hosts. Both may also feed on the seeds of several types of maples. One of the highest populations of boxelder bugs that I've ever observed were on a silver maple (A. saccharinum). I've never found goldenrain tree bugs feeding on maples in Ohio, but they are reported to infest maples in the southern U.S. This shouldn't be surprising given that maples also belong to the soapberry family, Sapindaceae.
Both bugs may also feed on the fruit of plums, cherry, peach, and grapes. As seed-feeders, the bugs cause no harm to the health of fruit trees. However, their feeding activity on tree fruit has been known to reduce fruit quality.
Goldenrain tree (K. paniculata) and Chinese flametree (K. elegans) were commonly planted in the southeastern U.S. as ornamentals. These Asian natives eventually escaped captivity to become widely naturalized. The widespread availability of these non-native soapberry trees produced a windfall of new food for the native Jadera bugs.
The bugs that have taken full advantage of Asian soapberries are showing several new and consistent features compared to bugs that remained feeding on native soapberries. The different Jadera bugs have not been separated taxonomically, but are referred to as "host races" based on morphological and developmental differences tied to the native and non-native hosts. Research has shown the evolutionary changes to the bugs occurred rapidly; it only took 20 – 50 years.
The most recent research has focused on comparing Jadera bugs that remained loyal to the native balloon vine (Cardiospermum corindum) with bugs that have been lured away by Asian cuisine to feed on the non-native Koelreuteria. On a side note, all Cardiospermum aren't equal. C. halicacabum is considered a non-native invasive that is gradually spreading from Florida northward, but that's another story.
The native balloon vine produces large seed pods with the seeds buried deep within. The Jadera bugs that evolved to feed on these seeds have very long mouthparts (beaks); about 70% of their body length. Koelreuteria seed pods are smaller in diameter with the seed closer to the surface and they mature rapidly to split and expose the seeds. Bugs that specialize in feeding on the non-natives have much shorter beaks.
Balloon vine produces seed over an extended period, so the bugs can take longer to develop. They are also rewarded for expending energy on developing strong flight muscles which allow them to find the native balloon vine which is not nearly as widespread as Koelreuteria.
Koelreuteria develops fruit over a much shorter period and fruit production is synchronized; there's a lot of food, but it's only available for a short time. Jadera bugs that have become specialists on the non-native Koelreuteria have much shorter developmental times; they need to reproduce quickly.
Also, these specialists don't waste energy developing strong flight muscles. They are rewarded with a lot of food if they stay with their host tree. I've noticed that these bugs don't fly off if handled. A peculiarity with these specialists is that adults develop shorter wings under high population densities. This is something that I observed in 2012-13.
You Can Never Go Back
The evolutionary changes have come at a cost. Jadera bugs that have become specialists on Koelreuteria can't go back to balloon vine. This has potential ramifications for the ecosystems in which this bug species originally evolved. In effect, the overall influence of the non-native food source is driving a change in an insect that was part of the ecosystem for tens of thousands of years. Thus far, the impact has not been fully determined.
Goldenrain Tree Bugs in Ohio
Goldenrain tree bugs were commonly found feeding on Koelreuteria in southern and central Ohio in 2012 and again in 2013 with their range extending to Wooster. They were also reported in Maryland and New Jersey. However, the bugs virtually disappeared from Ohio in 2014 perhaps due to harsh winters putting the kibosh to this southern insect's forays into the north.
I've been seeing a gradual return of these bugs to Ohio starting in 2017. However, the numbers have not yet been nearly as dramatic as in 2012-13. If you're finding goldenrain tree bugs on its namesake host, I'd like to hear from you with what you're observing and your location. Just click on my name at the top of this Alert to get my e-mail address.