Participants in the 102nd Ohio Plant Diagnostic Workshop held on Wednesday in the OSU CFAES Secrest Arboretum, Wooster, OH, observed first-hand the wide host range of Hickory Tussock Moth (HTM) (Lophocampa caryae, family Erebidae). In fact, HTM was the most common general defoliating caterpillar found during the diagnostic walkabout portion of the Workshop.
Early-instar HTM were found feeding on birch (Betula spp.), hickory (Carya spp.), oak (Quercus spp.), willow (Salix spp.), and witch-hazel (Hamamelis × intermedia). The literature notes that HTM is also commonly found on black walnut (Juglans nigra), birch (Betula spp.), and maple (Acer spp.), as well as various fruit trees, including apple (Malus spp.) and pear (Pyrus spp.).
HTM is native to North America. The image below shows reports posted to iNaturalist as of today. As shown, HTM is most often encountered in the northeastern U.S., east of the Mississippi River, and in southern Ontario and Quebec, Canada.
HTM has one generation per season in Ohio. Winter is spent as pupae inside hair-covered cocoons located in the duff beneath host trees. Adults appear in late May to early June in Ohio. Females lay eggs in clusters on the underside of leaves.
I could find no recently published reports of the exact number of instars for HTM. A paper published in 1918 reported that the number of instars varies between 8 and 9. The same report notes changes in caterpillar appearances and feeding behavior as they develop through different instar stages.
Early instars have prominent black head capsules and range in color from yellowish-white to yellow. They are covered in short, black hairs arising from obvious black spots.
HTM caterpillars feed gregariously during the first 4 instars. They feed on the upper or lower leaf surfaces, depending on the plant host, removing the epidermis and mesophyll, leaving the leaf veins and opposite epidermis.
Their feeding behavior produces characteristic leaf “skeletonizing” damage. The appearance of "see-through" leaves is a good indicator that the caterpillars are afoot. The damaged tissue turns from green to brown as the season progresses.
The gregarious early instars practice synchronized molting behavior as shown in the image below. The image shows mass-molted skins beneath a thin layer of silk, which presumably prevents the caterpillars from falling from the leaf as they molt into the next instar.
Owing to their gregarious feeding behavior, the early instars produce the most obvious leaf damage. However, the damage is usually highly localized and confined to clusters of leaves within canopies of trees or shrubs. Of course, the impact could be significant on young, newly planted trees.
Beginning in the 5th instar, the caterpillars disperse, transiting from feeding gregariously to becoming solitary feeders and consuming entire leaves. However, they are normally so widely dispersed that their impact on overall plant health is minimal.
The later instars become adorned with prominent, long, stiff white hairs and short black hairs. The color patterns remain variations of a black-on-white motif but shift as the caterpillars molt through the remaining instars. The patterns range from thin black stripes across the back (tiger striping) to a row of black spots down the back. They also develop prominent tufts of long hair, which accounts for why HTM was originally grouped with the true tussock moths.
True tussock moths belong to the subfamily Lymantriinae. Despite “tussock” in the HTM common name, the moth belongs to the subfamily Arctiinae, which includes Tiger and Lichen Moths. Indeed, an alternative and more accurate common name for HTM is “hickory tiger moth.”
The hairs on HTM caterpillars have microscopic barbs; however, they are not attached to venom glands like the hairs and bristles on more dangerous caterpillars. Their defense modus operandi is strictly physical rather than chemical. The hairs can puncture the thin skin of children or older adults to produce localized rashes similar to reactions to the defense chemical, urushiol, found in poison ivy. Even though sensitivity ranges among individuals, it’s best to look, but don’t touch.
Although HTM is a general defoliator, appearing on a wide range of host plants, this native moth is seldom a serious pest in Ohio’s forests or landscapes. Control measures are seldom required to protect overall plant health.
A Bat Crazy Defense Strategy
The moth family name, Erebidae, is derived from the Greek Erebos, or Erebus, who was a deity inhabiting darkness, or gloom, in early Greek mythology. So, moths belonging to the family inhabit the dark; they are night fliers. Of course, this means they must deal with a notorious denizen of Stygian gloom: bats.
Through a convenient gift of evolution, members of the subfamily Arctiinae (tiger moths) have modified cuticular plates on their thorax, called “tympanal organs,” which function like eardrums to detect sound. They also have other modified thoracic plates, called “tymbal organs,” that produce sound. These two types of organs are not unique to tiger moths; however, few other insects combine their function to gain an insanely effective defense strategy against a biosonar-equipped insectivore.
The tympanal organs on tiger moths are “tuned” to receive the sound frequencies emitted by bats. When they hear the sound pulses from a bat’s biosonar, the moths respond using their tymbal organs to send sound frequencies that drive their foe bat-crazy by jamming, disrupting, and otherwise wreaking havoc on echolocation. The moth escapes becoming dinner for a befuddled bat.
I could find no references documenting that HTM practices bioacoustical warfare against bats. However, the defense strategy is so elegant that I had to include a description in this Alert.
Selective References
Dowdy, N. J., & Conner, W. E. (2019). Characteristics of tiger moth (Erebidae: Arctiinae) anti-bat sounds can be predicted from tymbal morphology. Frontiers in zoology, 16(1), 45.
https://link.springer.com/article/10.1186/s12983-019-0345-6
Isely, D. (1918). Orchard injury by the hickory tiger-moth (No. 598). US Department of Agriculture.
Kuspis, D. A., Rawlins, J. E., & Krenzelok, E. P. (2001). Human exposures to stinging caterpillar: Lophocampa caryae exposures. The American journal of emergency medicine, 19(5), 396-398.
https://www.sciencedirect.com/science/article/abs/pii/S0735675701050197?via%3Dihub
Neil, T. R., Shen, Z., Robert, D., Drinkwater, B. W., & Holderied, M. W. (2020). Thoracic scales of moths as a stealth coating against bat biosonar. Journal of the Royal Society Interface, 17(163), 20190692.
Neil, T. R., Shen, Z., Robert, D., Drinkwater, B. W., & Holderied, M. W. (2020). Moth wings are acoustic metamaterials. Proceedings of the National Academy of Sciences, 117(49), 31134-31141.
https://www.pnas.org/doi/abs/10.1073/pnas.2014531117
Stireman III, J. O., & Stetz, L. A. (2025) Notes on the Occurrence of Compsilura concinnata (Meigen) in Southwest Ohio, USA. The Tachinid Times, 38.
Villas-Boas, I. M., Alvarez-Flores, M. P., Chudzinski-Tavassi, A. M., & Tambourgi, D. V. (2016). Envenomation by caterpillars. Clinical Toxinology, 10, 978-94.
https://link.springer.com/rwe/10.1007/978-94-007-6288-6_57-1
