1. The Bag Shelter Caterpiller
Bag shelter caterpillars, members of the ‘processionary’ caterpillar family, are among the worst, and should on no account be touched. The larvae live inside a brown bag, made of silk, after which they are named, coming out in nighttime hours to feed on host plants such as beefwood.
When moving between plants and trees, bag shelter caterpillars go head to tail, forming the typical procession that gives rise to the naming of the family. The poison these creatures employ is nasty, and in Southern Brazil and Venezuela is considered a public health problem.
People who are unfortunate enough to touch one of these bag shelter caterpillars can suffer bleeding both external and internal because the venom is highly anti-coagulant. The caterpillars defend themselves with bristles attached to venom glands. The chemicals within the poison produced by the South American Silk Moth are potent enough that a human can easily bleed to death if affected by them.
2. The Saddleback Caterpillar
Saddleback caterpillars are truly obnoxious to the touch. Covered in stiff spines that are housed in potent poison glands, they are aggressive and sting when touched, however unintentional the contact. This can result in immediate swelling of the affected area, severe nausea and a nasty rash that takes days to clear up. These nasty creatures love hibiscus and palm plants, so be very aware.
3. The Puss Caterpillar
The Puss Caterpillar or woolly slug is the most poisonous caterpillar in the USA. This little monster will spit acid at any ‘attacker’ and is loaded with poisonous spines all over its body that cause extreme reactions on contact with human skin. Because these creatures can be mistaken for cotton balls as they are quite striking in appearance, people rashly pick them up and really suffer for it. This creepy crawler likes citrus trees, elms, oaks and many different garden plants, so do keep your eyes peeled.
4. The Cinnibar Moth Caterpillar
Cinnibar moth young have a taste for bitter tasting chemicals that render them inedible to predators and also use extremely colorful markings as a way of warding off the hunters. They are all covered in short hairs that cause irritation on contact with skin, and chemicals within the hairs can also lead to serious health problems in humans, though skin rashes are far more common. Nonetheless, problems such as atopic asthma, osteochondritis, renal failure, dermatitis and haemorrage have all been caused by these caterpillars in the past, so one needs to be very careful around them.
5. The Stinging Rose Caterpillar
The stinging rose caterpillar is one of the most colorful and attractive to be found anywhere on the planet. Pairs of long, horn-like, bristly spines can be located along the body length, along with groups of smaller spines that are characteristic of this species. The caterpillar does, as the name suggests, sting, but the effects are fairly minor, though initially painful. This lovely little beast can be found in apple, oak, sycamore, dogwood trees and also on rose bushes, so keep your eyes open.
6. The Monarch Caterpillar
One of the most gorgeous of butterflies is the Monarch and its caterpillar in equally good-looking. Monarch caterpillars are very brightly colored, in those shades that most effectively warn of danger, namely black, red and yellow. Though these splendidly beautiful creatures are not harmful to the touch for humans, they are extremely poisonous because of the plants they eat.
7. The Hickory Tussock Caterpillar
An extremely attractive species of caterpillar, the hickory tussock moth is also one that is best avoided. Absorbing nasty chemicals for use as defences from the plants on which it feeds, these are secreted from the hairs on its body. On contact with human skin, severe itching usually ensues, accompanied by very painful burning sensations. Itchy rashes can persist for several days and are thoroughly unpleasant.
8. The Gypsy Moth Caterpillar
The gypsy moth caterpillar is a long-haired, highly colored specimen. Once found only in Europe and Asia, it was introduced to North America in the 19th century, since when it has greatly extended its range. Though not actually listed as one of the more potent of the ‘stinging hair caterpillar’ types, the hairs can still cause pain on contact and lead to dermatitis among more sensitive people in health terms.
9.The lo Moth Caterpillar
A superbly colored North American moth, the Io, has a truly lovely caterpillar that, as it develops, turns from orange to bright green, gaining hairy spines in the process. Looks, once again are deceiving, because the spines, on being touched, release a poison that causes a great deal of pain. It has a favourite food in the rose, so be aware if you have roses in your garden.
10. The Spiny Oak Slug Caterpillar
The spiny oak slug caterpillar is very attractive and colorful, but once again is not a creature you want to have crawling over your hand. It goes through several stages of development, all characterized by spiny tubercules along the back and sides that are attached to poison glands. These spines are known as ‘calltrop’ spines, as they supposedly resemble Roman defensive weapons, and they are painful to the touch, often causing a rash. Usually found in oak and willow trees, as well as other deciduous plants.