That's Not an Ant?!

It is always best to avoid making assumptions about insects in the field. I was reminded of that on three seperate occasions this month, all of them involving mimicry of ants by small longhorned beetles in the family Cerambycidae. Early spring is apparently the season for these wood-boring insects, at least here in Kansas. Their resemblance to ants is uncanny, and highly convincing.

Cyrtophorus verrucosus

While exploring our yards and looking for insects on April 2, I noticed what I thought was a carpenter ant climbing on the exterior of our detached garage. I was about to dismiss it, but decided to document it anyway, as it would be new for the year. Imagine my surprise and delight to discover it was instead an adult Cyrtophorus verrucosus. This species has no common name, which is unfortunate given its uniqueness.

The beetle averages only 9 millimeters in body length. Larvae bore in a variety of host trees, including maple, hickory, oak, elm, birch, chestnut, dogwood, Eastern Redbud, American Beech, and even pine. The adult beetles are active from March to July, but are most abundant in early spring. Cyrtophorus verrucosus ranges over most of the eastern U.S., and Canada as far west as Alberta. This was a new species for our property.

I was invited to present the keynote address for a joint meeting of the Kansas Academy of Science, and Central States Entomological Society, in Wichita, Kansas on April 5, and Heidi and I stayed over to go exploring on Sunday, April 6. I reached out to a Facebook and iNaturalist friend, Ryan Philbrick, and we met at the Kansas Wildlife Exhibit in Central Riverside Park. From there we went to Keeper of the Plains, and walked the nice concrete trail along the Arkansas River. At one point, Ryan turned over a small, broken tree limb on the ground. He noticed millipedes and a small "ant" crawling over the bark.

Euderces pini

I trained my camera on the ant and discovered it was another species of longhorned beetle, Euderces pini. At only 7-8 millimeters, and slender, it is even more ant-like than other species. The larval host trees include Flowering Dogwood, Pecan, Winged Elm, and American Beech, but there are several other hardwoods on the menu.

The adult beetles are frequently found on flowers, feeding on pollen and nectar. Even dandelions will suffice until native trees start blooming. Euderces pini occurs in the southern half of the eastern United States, and appears as an adult from March to June.

Currant-tip Borer

Back home, yesterday, April 13, I happened to notice a small ant-like insect on the central air-conditioning unit in the back yard. It was even smaller than the other beetles, but at least it had a common name: the Currant-tip Borer, Psenocerus supernotatus.

Despite its name, this 4-millimeter beetle has been reared from plants other than currant: Green Hawthorn, Tulip Tree (aka Tulip Poplar, Yellow Poplar), and Black Willow. This beetle is widespread in North America, east of the Rocky Mountains, and the adults are found from April to June.

None of these three beetles are considered pests, maybe because they do not affect crops or orchard trees. Their earthtone colors make them rather cryptic, but they are quite active, running rapidly, and flying well.

An actual ant

It is interesting to note the convergence in body shape and coloration between the different genera. They each have white streaks or bars designed to suggest body segmenation where there is none. Ants show marked constrictions between the head, thorax, and abdomen. In these beetles, the thorax may be mistaken for the enlarged head of an ant, and the elytra (wing covers), "divided" into thorax and abdomen by those white markings. The true head of the beetle is relatively small, and in the case of the Currant-tip Borer, directed downward and nearly hidden by the thorax.

There are even more ant-mimicking longhorned beetle species. Give that "ant" a second glance, especially if you see it in isolation, with no other ants nearby. It may turn out to be a beetle instead.

Sources: Lingafelter, Steven W. 2007. Illustrated Key to the Longhorned Woodboring Beetles of the Eastern United States North Potomac, Maryland: Coleopterists Society, Special Publication No. 3. 206 pp.
Yanega, Douglas. 1996. Field Guide to Northeastern Longhorned Beetles (Coleoptera: Cerambycidae). Champaign, Illinois: Illinois Natural History Survey, Manual 6. 174 pp.

Mate Guarding and Oviposition in the White-spotted Sawyer, Monochamus scutellatus (Coleoptera: Cerambycidae)

Please do not let the title of this post intimidate you. This would be a typical title for a paper in a scientific journal, but I promise to keep the language understandable, lively, and captivating. I also hope that you will be more likely to visit scholarly publications to learn more about the insect or arachnid subjects that interest you.

An impressive male M. scutellatus

I had the good fortune of stumbling upon a small sawmill in Black Forest, northeast of Colorado Springs, in June of 2016. The property owners, perhaps begrudgingly, gave me permission to look for insects in the stacks of Ponderosa Pine logs there, and it proved to be a "Beetle Bonanza." I visited on several occasions and found scores of jewel beetles (Buprestidae), longhorned beetle (Cerambycidae), checkered beetles (Cleridae), and a few bark beetles (Curculionidae: Scolytinae).

Among the more abundant species among the logs was the White-spotted Sawyer, Monochamus scutellatus. These are fairly large insects, 15-27 millimeters in body length, and members of the longhorned woodborer beetle family. The long "horns" refer to the antennae of these beetles. Males have antennae that may be twice the length of their bodies or even longer. The front pair of legs is also longer than in the females, and the front tarsi ("feet") are expanded to better grip the female during mating.

Male guarding a female

What I observed in one pair of sawyers prompted me to read about the mating behavior of the species, if only to confirm my hypothesis that the male guards the female he has mated with to prevent rival males from usurping his genetic investment in her offspring. It turns out there is even more to the story than I imagined, and I hope to observe those other behaviors at some point, too.

White-spotted Sawyers breed in dead, dying, injured, fire-scorched, or recently-felled pines, true firs, and Douglas fir, and spruce. Such resources are rather scarce in a forested landscape, so it pays males to stake them out with the understanding that eventually females will visit in order to lay their eggs (oviposit). Surprisingly, the males emit a pheromone that draws additional males to an oviposition site. The airborne chemical cue is called an "aggregation pheromone." Despite their size and ungainly antennae and legs, sawyers are accomplished fliers and easily make their way to the source of the pheromone.

Jaws of female Whitespotted Sawyer

Once there, the largest males with the longest antennae may square off in one-on-one duels for possession of the oviposition resource, which is the area of the tree trunk with greatest circumference. They lash at each other with their oversized antennae, and may grapple by locking their jaws and biting. Smaller males generally back off, giving way to larger rivals based on antenna-length alone. The dominant male mates with incoming females that may then disperse to lay their eggs. This is not what I observed, but the reference I am reading goes on to describe what I did record.

Mating, while female chews oviposition hole

I witnessed copulation between a male and female M. scutellatus, during which time the female was "multi-tasking," chewing a small cavity in the bark. At the conclusion of mating, the female turned around to deposit at least one egg in that cavity while the male continued to grasp her in a loose but protective embrace. She then turned again and appeared to resume chewing the bark cavity, but perhaps she was grinding sawdust to cover her egg.

Female ovipositing while male guards her

Fret not about the smaller male beetles, they may achieve mating success by protecting a less optimal tree bole; and they may profit from the expensive production of aggregation pheromone by other males. Smaller males are usually more agile and vigorous than their larger conspecifics.

The entire life cycle of the White-spotted Sawyer takes from one to two years as the larva that hatches from the egg bores first under the bark, then tunnels deep into the wood, sometimes reaching the heartwood. It eventually pupates in a cell near the surface, metamorphosing from a larva into an adult beetle. Once it leaves the pupa, it remains in the pupal cavity while its new exoskeleton hardens. It then chews its way to freedom, a journey that is clearly audible to the human ear.

Female resumes gnawing, covering her egg?

It is important to note that this species, like the overwhelming majority of other longhorned beetles, is not a forest pest. Yes, it can negatively impact logs in situations like the sawmill, before they are cut, but they do not kill living trees outright like the invasive Asian Longhorned Beetle, Anoplophora glabripennis. Sawyers are an important and charismatic part of the invertebrate fauna in coniferous forests across Canada and the northern U.S., and major mountain ranges farther south.

Sources: Coin, Patrick. 2004. "Species Monochamus scutellatus, Whitespotted Sawyer," Bugguide.net
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. Washington, DC: U.S. Department of Agriculture Miscellaneous Publication No. 1339. 654 pp.
Wang, Qiao (editor). 2017. Cerambycidae of the World: Biology and Pest Management. Boca Raton, Florida: CRC Press. 628 pp.

Beetle Bonanza

Back on June 13, while my wife and I were headed to a different destination, we passed by a logging mill operation in Black Forest, northeast of Colorado Springs. I wanted to go back another time, and did so on my own this past Thursday, June23, but not without much trial and error. It was a rewarding outing once I got there, with beetles of all kinds flocking to the freshly-cut Ponderosa Pine logs.

Jewel beetle, Chrysobothris dentipes

It turns out I had not been paying enough attention to the route we had taken the first time, and so on Thursday I became hopelessly lost. I phoned my wife and she informed me I was nowhere near the right road. Consequently, I got to the site in the late morning. When I arrived, there was no one to be seen. I looked around anyway, as there were also no postings against trespassing.

The first insects I saw were what I expected: medium-sized jewel beetles, Chrysobothris dentipes, as depicted above. These members of the family Buprestidae look exactly like little shards of pine bark, but they move often enough to be easily seen. Several males were engaging in "butt-thumping" displays to nearby females. Below is a very brief video depicting this. It is surprisingly audible, and also hilarious. I hope to go back again and get a longer video segment.

Also present were a fair number of the magnificent metallic green Phaenops gentilis. Though they are only about 8 millimeters in length, these buprestids are still conspicuous. Like most jewel beetles they are quick to fly when disturbed, though they usually simply run so erratically as to be nearly impossible to get an image of. Females pause often to lay eggs, though, so that is your one opportunity. The one below took time to groom itself and luckily I was in the right place at the right time.

Jewel beetle, Phaenops gentilis

While I was photographing another insect, I glanced down to see a very large buprestid that had landed on my shoulder. I grabbed it, and it turned out to be a Western Sculptured Pine Borer, Chalcophora angusticollis. Measuring 20-33 millimeters, they are among our largest jewel beetles. When they fly, the lifted elytra (wing covers) expose a bright blue, green, or violet abdomen. I brought it, and another specimen, home to photograph.

Western Sculptured Pine Borer

What surprised me most were the large numbers of predatory checkered beetles, family Cleridae, active hunters of bark beetles and other small insects. I thought that I was seeing one species, with individuals of varying sizes, but upon looking at my images it became apparent there were three species.

Checkered beetle, Enoclerus moestus

Enoclerus moestus was the first one I came across. E. lecontei was likewise common.

Checkered beetle, Enoclerus lecontei

Lastly, the largest species was the "Red-bellied Clerid," E. sphegeus. While the adult beetles will kill and consume a variety of other insects, the larvae appear to prey exclusively on bark beetle larvae. You know, like the Mountain Pine Beetle and its relatives that are often blamed for killing entire forests.

Red-bellied Clerid, Enoclerus sphegeus

Longhorned beetles were present on the log stacks as well. I expected the White-spotted Sawyer, Monochamus scutellatus, and indeed I found a couple of females, one of them ovipositing, and a single male. These are large beetles that live up to the longhorn name. Their antennae are exceptionally long, especially in the males.

Female White-spotted Sawyer laying eggs

The most abundant of the longhorns, though, were flower longhorns in the genus Grammoptera. I even found a pair mating.

Flower longhorned beetles, Grammoptera sp., mating

The freak of the longhorn show was the Ribbed Pine Borer, Rhagium inquisitor. The adults look very little like a typical longhorned beetle, having quite short antennae. Two specimens landed on me or in my vicinity.

Ribbed Pine Borer

They are medium-sized at 12-15 millimeters in body length. They get their name from the woven wreath-like ring consisting of coarse wood fibers that the larva creates for its pupal chamber.

I also found a few oddball beetles including a very tiny weevil, Lechriops californica. At least that is what I think it is. They bore, in the larval stage, under the bark on the trunk and larger branches of various pines.

Tiny weevil, Lechriops californica maybe

Another predatory beetle was a very small clown beetle, family Histeridae. It may belong to the genus Platysoma, which live under bark and hunt the larvae of flies and beetles.

Clown beetle, Platysoma sp.

There were non-beetle insects, too, of course. The most common were the syrphid fly Chalcosyrphus piger. Females were alighting on the logs, presumably to oviposit (lay eggs) there. The larvae of these flies feed on decaying wood, and perhaps fermenting sap.

Syrphid fly, Chalcosyrphus piger

The most exciting find was a female aulacid wasp, family Aulacidae, in the genus Pristaulacus. They are easily mistaken for ichneumon wasps at first glance, but the ovipositor is downcurved at the tip; and the abdomen is connected high on the back of the thorax. These wasps are more closely allied to ensign wasps (Evaniidae) and carrot wasps (Gasteruptiidae). They are parasites of wood-boring beetles, surprise, surprise.

Aulacid wasp, Pristaulacus sp.

I am looking forward to returning to this site, as long as I am welcome. Those towering stacks of big pine logs are a bit intimidating, I have to admit, but worth braving for the bounty of beetles.

Male longhorned beetle, Acanthocinus obliquus

Sources: Cowan, B.D. and W.P. Nagel. 1965. "Predators of the Douglas-Fir Beetle in Western Oregon," Technical Bulletin 86, Agricultural Experiment Station, Oregon State University, Corvallis, Oregon. 32 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. Miscellaneous Publication No. 1339, U.S. Department of Agriculture, Forest Service, Washington, DC. 654 pp.
Smith, David R. 1996. "Aulacidae (Hymenoptera) in the Mid-Atlantic States, with a Key to Species of Eastern North America," Proc. Entomol. Soc. Wash.. 98(2): 274-291.

Wasp Wednesday: Not Wasp IX

I have recently begun participating in “Project Noah,” and as a result find yet another demand for identification of mystery bugs, like this one posted just yesterday. The subject of the image is a Red-necked Ash Borer, Neoclytus acuminatus, a type of longhorned beetle in the family Cerambycidae.

The person who posted the image says he calls them “crickabees” because they have “legs like a cricket….and stripes like a bee.” Most folks mistake these beetles for wasps, though. They can be fast-moving insects, a trait not always associated with beetles. Couple that with their bold markings, and it would be easy to assume they are a stinging insect.

Despite its name, this beetle bores in virtually any hardwood tree during its larval stage, though it does seem to favor ash. It has also been recorded from woody vines and shrubs. I have noticed the adults on freshly-cut trees, but also on older logs. While dead, dying, or weakened trees are most commonly exploited by the Red-headed Ash Borer, it is also a serious pest of healthy black locust trees planted as windbreaks or on farm woodlots. It may also attack recently-planted trees. So, trees stressed in some way are going to be vulnerable to this beetle.

References indicate that the normal flight period for Neoclytus acuminatus is between May and August in the northeast U.S., and from February to November in the southeast. There may be up to three generations each year in the south, usually only one in the north. Firewood brought indoors in late winter or early spring may yield adult beetles emerging inside your home.

This species is widespread, found almost everywhere east of the Rocky Mountains (and into Idaho). It is not one of the larger longhorned beetles, adults measuring only 4-18 millimeters in length.

Sources: Shour, Mark. 2008. “Red-headed Ash Borer Also a Threat to Ash Trees,” Extension News.
Solomon, J.D. 1995. Guide to Insect Borers of North American Broadleaf Trees and Shrubs. Agric. Handbk. 706. Washington, DC: U.S. Department of Agriculture, Forest Service. 735 pp.
Yanega, Douglas. 1996. Field Guide to Northeastern Longhorned Beetles (Coleoptera: Cerambycidae). Illinois Natural History Survey Manual 6. 184 pp.

Wasp Wednesday: Not Wasp VII

Imagine one’s surprise at finding wasps suddenly appearing inside their home in the middle of winter. It is not impossible, as queen yellowjackets and some female paper wasps hibernate, overwintering inside houses and other human structures. They may stir if they find their way inside to heated rooms. However, other kinds of insects can be mistaken for wasps. I recently had occasion to identify one such masquerader.

One of the keepers at the Cheyenne Mountain Zoo here in Colorado Springs discovered wasp-like insects emerging from woody “perching material” used for birds in the African Rift Valley exhibit. To her credit she recognized them for what they really were: beetles.

These insects are black with yellow stripes, superficially resembling the markings of yellowjackets. They also run very rapidly, which enhances their resemblance to stinging insects. Many species of longhorned wood-boring beetles in the family Cerambycidae are convincing wasp mimics, and indeed that is what these specimens turned out to be. It was a bit more challenging to determine exactly which genus and species.

It helps to know what a beetle’s “host plant” is when trying to identify it. This only applies to herbivorous species, of course, but it is surprising how many vegetarian beetles feed on only a handful of different plant species. A variety of dead limbs from native hardwoods and conifers are used by zoo personnel for structural objects in exhibits, or as enrichment items to make life in captivity more humane and enjoyable for the animals. So, I knew the beetles were of local origin rather than something imported accidentally from overseas.

From my experiences in Oregon, I had my suspicions as to what genus this beetle belonged to: Neoclytus. There are 25 species in North America, so the next step was determining which ones are found in Colorado. Using a publication on Colorado Cerambycidae (Heffern, 1998), I learned that there are five, maybe six species of Neoclytus known from the Centennial State.

I was able to go online and look up images of the common Colorado Neoclytus species, and the only one to match the specimens given to me by the zookeeper was the Banded Ash Borer, Neoclytus caprea.

Although ash (Fraxinus spp.) is the favored host, the Banded Ash Borer is known to bore in a variety of dead and dying trees. Netleaf Hackberry (Celtis reticulara), hickory (Carya spp.), elm (Ulmnus spp.), oak (Quercus spp.), mesquite (Prosopis spp.), walnut (Juglans spp.), eucalyptus (Eucalyptus spp.), and grape (Vitis spp.) are all hosts to the wood-boring larval stage of this beetle. Trees weakened by drought, disease, fire, and attacks from other insects are especially vulnerable. Rarely are healthy trees attacked.

Adult beetles normally emerge in early spring. After mating, females lay eggs in bark crevices of the host tree. The larvae that hatch from the eggs tunnel just beneath the bark before boring into the sapwood where they feed for most of the summer. The larvae pupate in autumn and overwinter in that stage.

The adult beetles measure 8-17 millimeters, size being a function of the amount of nutrition received in the larval stage. This is a widespread species, found throughout the U.S. except for the Pacific coast. It also ranges into eastern Canada. Look for adults outdoors from March to June. They emerge on the early end of that spectrum in more southerly latitudes.

Ash logs felled in winter are especially prone to attack by the beetles in the following spring. Infested logs brought indoors for firewood may spawn an early emergence of the beetles due to the artificial warmth and extended “daylight” presented by indoor stimuli.

Milling of infested timber may actually prolong the life cycle of wood-boring beetle larvae that survive the process. Dry wood may offer less nutritional value to the grubs trapped within it, meaning that a normal yearly life cycle may be extended to several years in the case of the Banded Ash Borer.

The next time you find a swarm of “wasps” in your home, check the firewood first, and see if it might not be beetles like the Banded Ash Borer, the Hickory Borer, or a related species. Relax, they are at most a nuisance.

Sources: Heffern, D. J. 1998. “A survey of the Cerambycidae (Coleoptera), or longhorned beetles of Colorado,” Contributions of the C. P. Gillette Museum of Arthropod Diversity. Colorado State University: Department of Bioagricultural Sciences and Pest Management. 32 pp.
Karren, J. B. and Alan H. Roe. 2000. “Banded Ash Borer,” Fact Sheet 11, Utah State University Extension.
Yanega, Douglas. 1996. Field Guide to Northeastern Longhorned Beetles (Coleoptera: Cerambycidae). Champaign, Illinois: Illinois Natural History Survey Manual 6. 174 pp.