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.
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.
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.
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.
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.