As I write this, Leavenworth, Kansas, USA, is under an (checks notes) “extreme heat warning,” expected to last for another two days at least. It has been an excessively hot summer, and I am recounting memories from spring more than I am making new discoveries. One thing that stands out was the diversity of jewel beetles, family Buprestidae, that I found during the month of May this year.
Jewel beetles are also known as metallic woodborers for their often brilliant, iridescent colors; and called flathead borers for the flattened larval stage. The adult beetles are frequently alert, dashing or flying away at the first hint of potential danger, making them a challenge to photograph. Others are exceptionally cryptic, relying on camouflage and stillness to avoid detection in the first place. Some species exhibit all of these characteristics and behaviors.
Yes, some species can be pests, namely the Emerald Ash Borer, Agrilus planipennis, but that is a species native to east Asia. It is extremely problematic where it has been introduced. Most jewel beetle species are kept in check by parasitoid wasps, predatory beetles, and other natural controls.
On May 4, Heidi and I went across the river to Weston Bend State Park in Missouri, one of our favorite haunts during spring bird migration. It turned out to be pretty good for insects, too, including some jewel beetles. I spotted one of the many species of the genus Agrilus that can be found in our neck of the woods. These are small, usually well under ten millimeters, very narrow and elongate, and more often than not have muted colors. They are most often seen on foliage in sunny spots in the forest understory, or along forest edges.
Heidi, while taking pictures of moss or mushrooms on a stump, suddenly exclaimed that she saw a huge buprestid. Indeed, she found a big specimen of the Hardwood Heartwood Buprestid, Texania campestris. It is very likely the largest species of jewel beetle in our immediate area, ranging from 20-30 millimeters. It can be confused with the pine-boring genus Chalcophora that is found elsewhere in Missouri.
T. campestris occurs east of the Great Plains, but is more common in the southern U.S. than elsewhere. Known host plants for the larvae include American Beech, American Sycamore, maples, and Black Willow.
Closer to home, I visited Havens Park here in Leavenworth, on May 13. It is the closest thing to a “wild” park within walking distance. It is a hilly park, at the top of which is something of a plateau. There, at the summit, more or less, is a degraded glade habitat, more xeric than the surrounding forest, dominated by Eastern Redcedar, and some of the hardier oaks.
I found a handful of jewel beetles flying around, and landing on, some oak saplings in one sunny spot. They turned out to be the Blue Spotwood Borer, Agrilus acutipennis, infrequently to rarely collected, according to one recent source. This is a spectacular species for the genus, at 7-10 millimeters in length, and vivid metallic blue with white scales highlighting the edges of the pronotum (top of thorax), and the sides and venter of the abdomen.
The Blue Spotwood Borer is found east of the Great Plains, well into Canada. Larvae are known to bore in Eastern White Oak, and Overcup Oak, but the adult beetles alight on all kinds of other oaks, hickories, and walnut.
In contrast to that showy species, I also noticed a Brachys ovatus, doing its best impression of a dried-up leaf edge. At only 4-7 millimeters, it is easily overlooked despite how relatively common it is, throughout eastern North America. Oddly, males of this species are rarely seen, and it may reproduce by parthenogenesis. Larvae bore in Northern Red Oak.
I also found an unusually lethargic Common Hackberry Agrilus, Agrilus lecontei, also on an oak leaf. I thought it might even be dead, a victim of a robber fly or other predator. I collected it into a vial, and by the time I got home it was apparent it was very much alive.
This is another small (4-7 mm) species that is supposedly uncommon, despite its widespread distribution east of the Great Plains.
We have several Eastern Redbud trees “volunteering” in our yards, so it was not surprising to discover a Redbud Borer, Ptosima gibbicollis, on one of them on May 18.These little beetles are only 4-7 millimeters, but black with bright yellow markings, so they are easy to see.
On May 20, I was surprised and delighted to spot a Two-lined Chestnut Borer, Agrilus bilineatus, on a leaf near our front steps.
Despite the name, this beetle uses a variety of oak species as host trees. It is a widespread and common species east of the Great Plains, but this is the first time I have seen one. It is 4-10 millimeters long.
I walk our neighborhood regularly, weather permitting, but on May 22 I took only my phone with me. Naturally, I found a lovely specimen of Anthaxia cyanella on a leaf in a hedge adjacent to an open field.
This brilliant blue beetle is only 4-5 millimeters long, and is apparently infrequently encountered. Larvae are known to bore in Eastern Redbud, Honeylocust, Downy Serviceberry, and River Birch. Adult Anthaxia species in general are usually seen on flowers, especially composites.
On May 26, once again with only my phone at hand, I noticed a Beech Borer, Agrilus obsoletoguttatus, in the little butterfly garden along one exterior wall of our local library.
This beetle, 4-8 millimeters in length, is quite common east of the Great Plains. Larval host trees include Dwarf Chinkapin Oak, Northern Red Oak, Ohio Buckeye, Eastern Hophornbeam, and Honeylocust, among others.
Heidi and I hiked the VA Trails, another mostly wild park along the Missouri River on the Kansas side here in Leavenworth, on May 27. I didn’t see any jewel beetles until we came back to the parking lot and I noticed a large, recently-downed limb of an oak tree about fifty yards away.
Storm damage provides woodboring beetles of all sorts with fresh resources that they quickly locate and oviposit into. Among the more reliable arrivals will be jewel beetles in the genus Chrysobothris. The bad news is that they all look very similar and are extremely challenging to identify.
Sure enough, I found several of these cryptic gems running over the bark of the tree limb. The Chrysobothris femorata species complex is probably what this one falls under. The species is named the Flatheaded Appletree Borer, but there is a wide range of deciduous trees used as hosts. These are probably opportunistic generalists that take advantage of storm damage and logging operations. Chrysobothris are midsize jewel beetles, ranging from 7-16 millimeters in this particular instance.
Jewel beetles can be found during most of the warmer months, but spring, even early spring, is perhaps the best time to be looking for them. They are well worth pursuing, and you can help add to our collective scientific knowledge by sharing your observations on iNaturalist, Bugguide, and elsewhere. Happy Hunting!
Sources: Paiero, Sten M., et al. 2012. Field Guide to the Jewel Beetles (Coleoptera: Buprestidae) of Northeastern North America. Canadian Food Inspection Agency. 411 pp.
Solomon, J.D. 1995. Guide to Insect Borers of North American Broadleaf Trees and Shrubs. Agriculture Handbook 706. Washington, DC: U.S. Department of Agriculture, Forest Service. 735 pp.
