Poisonous Caterpillars in New York?!

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Written By Peter Morris

Moth adult

Description

Fall is caterpillar season. It's common to see them crawling around prior to spinning their cocoons for the winter, where they'll spend the cold months and emerge as adult moths and butterflies in the spring. Some species of moth caterpillars in New York, although attractive to look at, can sting. They possess hollow, quill-like hairs connected to venom sacs in their body which are used as defensive weapons to discourage birds and other predators from feeding on them. When these hairs or spines are touched or broken, the venom is released. Some hairy or spiny butterfly caterpillars are also out there, but they lack the venom possessed by the five moth caterpillars noted below. The ability to sting, though, only exists in the critter's caterpillar state and not during their adult moth or butterfly stages of life. At least they are not aggressive the way yellow jackets can be! 

 Stinging Hairs

These are strictly for defense - the hollow hairs are connected to poison glands that secrete toxins. The chemical cocktail is species-specific, and often involves serotonin, histamine, formic acid and various amino acids. 

beware those stinging hairs !

 The hairs inject their charge only when the critter is roughly handled. Unfortunately, their stings cause a painful rash which may persist for a week or more. Some people have more severe reactions, requiring medical treatment. 

Toxin response

 Reactions to certain stinging moth caterpillars depend on the person, their skin sensitivity, and allergies.Some people will range from nothing to mild itching, or maybe something comparable to a bee sting. Others can have a great deal of swelling, severe rashes, and even intestinal disturbances.Most important is to note that hairs can induce asthma as they are very fragile, and they readily become airborne when broken off. Eastern and Forest tent caterpillars, as well as gypsy moths, and even the beloved woolly bears can also trigger asthma attacks in some people. 

adorable woolly bear

First aid

 The best thing to do in case of a sting is to use Scotch or packing tape on the skin to pull out any embedded caterpillar hairs. Wash the affected area and isolate any clothing you suspect may harbor stray hairs.Monitor the affected person for several hours for signs of a serious reaction, and otherwise treat the rash the way you would any sting. Use calamine lotion, antihistamines, or hydrocortisone lotion as directed by your doctor. 

rash !!!

The following are moth caterpillars to avoid:

Saddleback Caterpillar (Archaria stimulea)

 The saddleback caterpillar is typically found on deciduous trees such as basswood, chestnut, cherry, oak, and plum.The pompoms bear urticating hairs that secrete irritating venom. The stings are very painful, and they can cause swelling, nausea, and leave a rash that can last for days. 

Saddleback

Spiny Oak Slug Caterpillar (Euchlea delphinii)

 This one is pale yellow/green colored with four dark patches of spines toward the rear and numerous spiny, yellow or red fleshy lobes.They feed on oak, beech, chestnut, willow, pear, bayberry, sour wood, and other trees.Touching them can result in a bee-like sting, but not as intense as a saddleback caterpillar. 

slug indeed !

Io Moth Caterpillar (Automerios io)

 Io moth caterpillars feed on a wide variety of plants including roses, willow, linden, elm, oak, locust, apple, beech, ash, currant, and clover.The frond-like spines have a painful venom that is released with the slightest touch. Some people experience severe reactions and require medical attention, while some only itch or have a burning sensation. 

fuzzy green !

Hag (Monkey Slug) Caterpillar (Phobetron pityhecium)

 It looks like a dried leaf !It is found on lower branches of assorted trees and shrubs, including oak, chestnut, dogwood, sassafras and ash. The caterpillars are usually seen feeding on the undersides of leaves.It has six pairs of curly projections densely covered in hairs. These can fall off without harming the larvae and will cause some fierce irritation. 

strange and hairy

Hickory Tussock Caterpillar (Lophocampa caryae)

 Pretty. Velvety back and sweeping bristles, this caterpillar looks more like a vintage feather boa than larva.Although some people have little to no reaction to this caterpillar, others have a reaction that ranges from a mild to a severe rash comparable to poison ivy. 

Tussock moth caterpillar

 Speaking of moths ….. Millions of Spongy Moths Threaten New York landscapes (at least they are not poisonous).2024 was an especially bad year for spongy moths. Formerly known by the insensitive name "gypsy moth", the invasive species was brought to America from France over 100 years ago in an attempt to breed them with silkworms to create stronger fabric. 

spongy moth

Check your garden for hairy caterpillars !!!!!

Call us if you need help ! 

PLANT SPECIALISTSGREENING NEW YORK FOR OVER 53 YEARS !

   Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBAAll photographs used with permission @SHUTTERSTOCK

Peter Morris

Peter was born and raised on a beautiful green island in the midst of a tropical rainforest. He was introduced into the world of plants at the age of six when his grandmother, an avid Spanish gardener herself, asked him to help her grow seeds for her pepper garden. He was hooked! By the time he was a teen, he had his own rose and orchid collection numbering in the hundreds. Botany was in his blood, and that is what he set out to study.

His passion brought him to NY in the late seventies to further his education. His tenacity allowed him to work full time at Plant Specialists while he completed a MS in Plant Biology. As a manager at the time he felt unsatisfied with his knowledge of business and business processes. Peter felt compelled to learn, so he then pursued and completed an MBA in Quality Management within a few short years.

Peter’s other passion is teaching. His natural ability is quickly consumed by our staff in all subjects in Botany, Horticulture, and Landscaping. He created an immense reference library of more than 3,500 plants providing an invaluable resource for our staff.

Peter’s breadth of knowledge and wisdom allows him to effectively diagnose the needs of plants. Sometimes just by walking into a garden he can create a prescription that fixes even the hardest issue. He is our Staff Botanist, Diagnostician, and all around Mentor. Recently, he has put his immense knowledge and skills into developing a new department that focuses on Plant Healthcare. As he puts it, “Magic through Science”. The PHC staff that surround him have avidly consumed his teachings. Substantially developing their own plant wisdom, many have taken on difficult plant health issues with spectacular results.

Plant Healthcare has been an instant success with customers! The proper treatment of insects and diseases including Organic methods has made pest control a necessity for every plant. Correcting hormonal imbalances caused by planting in containers or refurbishing soils leached of nutrients by irrigation systems are big challenges PHC has become quite comfortable addressing. The scientific approach to the complex demands of keeping plants healthy in our harsh city environment has made many a customer say WOW!

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