Hibiscus Scentless Plant Bug Life Cycle

It is a rare occasion when I am able to document all life stages of an insect species, let alone in the same location, or over a period of a couple of days. That is what happened, though, when I photographed a population of a scentless plant bug, Niesthrea louisianica, sometimes called the Hibiscus Scentless Plant Bug. Indeed, hibiscus and related plants in the family Malvaceae are their hosts. Our saga takes place in Okawville, Illinois, USA, in October of 2023.

While exploring the yard at my sister-in-law's home, I happened to notice adults and nymphs of this insect on buds of what I learned later was the plant known as Rose-of-Sharon, Hibiscus syriacus. Even the adults are not very large, measuring only 6.5-8.5 millimeters in body length. They are noticeable because they are so brilliantly colored in orange and red, with legs annulated (banded) in black and white. Niesthrea louisianica is a mostly southern U.S. species, but ranges from New York to Florida, and west to Iowa, Texas, Arizona, Utah, and California.

Apparently it is not unusual to find all stages in the life cycle at the end of the plant's growing season, and the adult insects overwinter anyway. Females can live about two months, males roughly fifty days. There can be at least three or four generations per year in southern latitudes, fewer farther north. Females deposit eggs in small batches, up to 36 in number, on the underside of leaves, beneath the bracts of the flower buds, or on the seed heads. One female can lay up to seven hundred eggs in her lifetime. I spotted a couple of egg clusters, one being guarded, presumably by the female that laid them.

The first instar nymphs that emerge from the eggs are so tiny! This species goes through five instars, an instar being the interval between molts. Like all true bugs, metamorphosis is "simple," each instar incrementally larger than the last, with the final molt to adulthood resulting, in this case, in a winged, sexually-mature individual. All life stages feed on the flower buds and seeds of the host plant, inserting the stylets of their rostrum to reach the interior fluids and tissues.

The activity period of the Hibiscus Scentless Plant Bug differs with latitude, but the life cycle begins in April or May, when the overwintered females lay eggs. It concludes with the end of the growing season, in October or even later.

One interesting aspect of Niesthrea louisianica is its potential role in controlling a problematic plant called Velvetleaf, Abutilon theophrasti. The bugs can carry pathogenic fungi in the genera Fusarium and Alternaria, which ride on the insects and infect the seeds of the plant, weakened from the feeding activities of the insect.

The "scentless plant bug" moniker may not apply in the case of the Hibiscus Scentless Plant Bug. They possess metathoracic glands, and a single dorsal abdominal gland, that produce copious amounts of exocrine chemicals for self-defense. Not that this deters spiders, one of their chief enemies, nor does it prevent parasitoid tachind flies, genus Leucostoma, from attacking the adult bugs. Scelionid wasps, genus Telenomus, exact a toll as parasitoids of the bug's eggs.

This is one of those species that fits the entomological addage of "Once you see one, you will see them everywhere." They are "locally abundant," like many host-specific phytophagous (plant-feeding) insects. They will not be on every plant because the defensive chemicals of the host plant vary from one individual plant to the next. Be on the lookout for them in Ohio, Indiana, and northern states currently out of their accepted range. Climate change may be driving a northerly range expansion.

A pair of less colorful specimens from Cape May, New Jersey, September, 2017

Sources:Baker, James. 2016. "Hibiscus Scentless Plant Bug," NC State Extension Publications
Kremer, Robert J. 1992. "Integration of a Seed-feeding Insect and Fungi for Management of Velvetleaf (Abutilon theophrasti) Seed Production," Proceedings of the Eighth Annual Symposium on Biological Control of Weeds.
Jones, Walker A., H.E. Walker, P.C. Quimby, and J.D. Ouzts. 1985. "Biology of Niesthrea louisianica (Hemiptera: Rhopalidae) on Selected Plants, and its Potential for Biocontrol of Velvetleaf Abutilon theophrasti (Malvaceae)," Annals of the Entomological Society of America 78(3): 326-330.
Slater, J.A., and R.M. Baranowski.1978. How to Know the True Bugs. Dubuque, Iowa: Wm. C. Brown Company Publishers. 256 pp.
Moorehouse, Angella. 2023. Flower Bugs: A Guide to Flower-associated True Bugs of the Midwest. Minnetonka, Minnesota: Pollination Press, LLC. 360 pp.
Steill, Jennifer, and Jason Meyer. 2003. The Rhopalidae of Florida "Scentless Plant Bugs." Insect Classification Project. 23 pp.

A group of juveniles on an unidentified host plant, New Jersey

Red-shouldered Bug

Today’s edition of “True Bug Tuesday” is all about the Red-shouldered Bug, Jadera haematoloma, family Rhopalidae. Last week, my wife and I happened upon a large number of this species in various life stages here in Colorado Springs. I went back a couple of times to get more and better images.

At first glance, it is easy to mistake Red-shouldered Bugs with boxelder bugs in the genus Boisea. Indeed, they both fall under the more general category of “soapberry bugs,” named for the affinity of these insects for the fruits of certain trees in the family Sapindaceae. Their appetite extends far beyond the berries and seeds of those and other trees and plants, though. They have been observed feeding on flower buds, oozing sap, and even dead insects.

Adults of Jadera haematoloma are overall slate gray with fewer red markings than boxelder bugs. They measure 9.5-13.5 millimeters in body length. Some specimens are brachypterous, meaning they have shorter wings than normal, revealing a bright red abdomen with a black bar or two on those exposed segments.

Nymphs lack wings, so the front half is gray while the back half is red. The nymphs can get very bloated while feeding, as demonstrated by the one imaged below. The nymphs pass through five instars (an instar is the interval between molts) before reaching adulthood. Freshly-molted adults are bright pink or orange.

There are usually at least two generations per year, more in the southernmost states. The bugs mate “tail-to-tail” and are thus easily distinguished from solitary individuals. Females unreceptive to mating signal that fact to approaching males by making noise. They stridulate by rapidly rubbing lateral edges of the abdomen against the adjoining thoracic segments.

A mated female digs a hole about one centimeter in depth in dry soil. There, guarded by the male, she lays a batch of up to twenty eggs. The ova hatch in about two weeks. One female, which usually mates multiple times with different males, can produce between 400 and 800 eggs in her adult lifetime.

Both nymphs and adults can overwinter in cracks, crevices, and other cozy niches. They occasionally take shelter inside homes and other buildings like boxelder bugs, rendering them a “nuisance pest” in some places.

The Red-shouldered bug is also known as the Goldenrain Tree Bug. It is native to the U.S. from Virginia south to Florida and west to Wisconsin, Kansas, Colorado, Arizona, and southern California. South of the border the species occurs from Mexico and the Caribbean to Colombia and Venezuela. It has also been accidentally exported overseas, at least to Asia.

This insect is easily confused with boxelder bugs, and any number of seed bugs in the family Lygaeidae which can be of similar size, coloration, and abundance. One must look at various subtle structural characters, rather than color and pattern, to distinguish them with any degree of certainty. With practice, however, one can render a confident ID in the field.

Sources: Carroll, Scott P. 2013. “Jadera haematoloma,” Soapberry Bugs of the World.”
Eaton, Eric R. and Kenn Kaufman. 2007. Kaufman Field Guide to Insects of North America. Boston: Houghton Mifflin Company. 392 pp.
Jing-Fu Tsai, et al. 2013. “The soapberry bug, Jadera haematoloma (Insecta, Hemiptera, Rhopalidae): First Asian record, with a review of bionomics,” Zookeys 297: 1-41.
Slater, J.A. and R.M. Baranowski. 1978. How to Know the True Bugs. Dubuque, Iowa: Wm. C. Brown Company Publishers. 256 pp.

Boxelder Bugs Revisited

It is that time of year again! No, not Halloween. No, not elections (and which of those two is more scary, anyway?). It is Boxelder Bug season. I imaged this one a couple of weeks ago at the Rea Farm in Cape May, New Jersey:

Rather than repeat myself, I’ll kindly refer you to the blog I did last year as part of my ”Indoor Insects of Autumn” series. The other three parts covered the Western Conifer Seed Bug, Brown Marmorated Stink Bug, and Multicolored Asian Lady Beetle. See if you can’t find some of these in your own neck of the woods this week.