These Black and Red bugs just appeared, have been here over 20 years and have never noticed anything that looked like these. They were swarming all over the myrtle (ground cover – not the Crepe Myrtle) also looks like they are mating. They were not damaging the plants. And we have lots of it around the yard but just seems to be on two clumps. At least 600 on top of leaves.
I think it is in the same family Rhopalidae. But I think it is the Red shouldered bug.
They are known to feed on the seeds of several trees. They, much like the boxelder bugs, do show up in clusters.
This is a bug found in the southern United States.
These bugs are known to feed on a variety of plants but prefers balloonvine which grows in southern Florida. Additional hosts include other plants in the soapberry family, Ficus spp. and hollyhock family. In some areas the bugs are observed feeding so often on goldenrain tree seeds, that they are referred to as ‘goldenrain tree bugs’. Your crape myrtle is in the loosestrife family. Nymphs and adults suck juices primarily from seeds but also suck juices from fruits of many trees. This can deform fruit.
This insect seems to be much like the boxelder bug as it is considered a nuisance rather than economically damaging. So there is no need to spray.
When we in the MidWest get lots of boxelder bugs on the outside of the house in the fall, we sometimes vacuum them with a shop vac, put them in a sealed bag and throw them away or in a bucket of soapy water. Doing that prevents so many from getting in the house.
If you only have a few I would not worry about them right now. They do not do any real damage.