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Garden Insects That Can Be Dangerous
In any wild or semi-wild environment, there will be insects and other creatures who have evolved self-defense mechanisms that predate humans by literally millions of years. When we encounter these creatures they may, understandably, deploy the self-protection techniques that have kept them on this planet for millennia, and that may result in you or me being stung or bitten.
This guide helps gardeners like me avoid being hurt by an insect in our garden. If you are stung or bitten by a garden insect, this article may help you understand exactly who it was that bit you, if not why.
Identification Chart for Dangerous Garden Insects
Puss moth/southern flannel moth caterpillar
Very furry, small, slug-like
Live in trees; sometimes drop out onto people
Bright green "saddle" on back; spines
Eat apple, rose, and other plants
Stinging rose caterpillar
Found on roses
Buck moth caterpillar
Large, brown, with dense spines in rosette form
Feed on oak trees, often in groups
Bright red and black; large
Fast, found on the ground
Large brown spiders with long legs
Quick spiders, not aggressive
Shining black with red "hour glass" marking
Hide in dark places like garden sheds
Very small, nearly invisible
Live in grass and wait for passing mammals
Small, brown or black, oval or round
Like chiggers, wait to grab onto passing hosts
Many legs, pincers, sting on tail
Shy but will sting if threatened
Shining brown, large, prominent pincers
Seldom seen; come out at night
Large, long legs, toothed "wheel" on back
Found on plants, searching for prey
Very small, fast, dark ants
Live in nests in flat grassy areas
Yellow and black, medium sized
Construct nests in the ground
Puss Moth or Southern Flannel Moth Caterpillar
The puss moth caterpillar has several names, including southern flannel moth and the "Elvis caterpillar," thanks to its swooping, luxurious pompadour. But all that hair covers up rows of sharp, highly toxic spines. Coming into contact with those spines cause intense pain that gets worse as the hours go on; a severe sting can send an adult to the emergency room. And if you are allergic to bee stings, the puss moth caterpillar can pose a serious health risk.
You can avoid this menace by being aware of the insect's appearance, and avoid the temptation to touch the luxurious "fur." However, this may not help you when one of these caterpillars drops out of a tree, as they tend to do later in the summer; many people are stung just standing under the wrong tree at the wrong time.
The instantly-recognizable saddleback caterpillar should be familiar to gardeners in across the southeast. These small, brightly colored caterpillars occur in small colonies and feed on apple, cherry, and rose, among other plants. Gardeners often come into contact with this species when pruning fruit trees or rose bushes.
The sting of the saddleback caterpillar is not severe, but it can be unpleasant, especially if several of them are involved, which is often the case. The sting is comparable to nettles.
Prevent caterpillar stings simply by wearing gloves, but be aware that they often cling to gloves, and people have been stung that way.
Stinging Rose Caterpillar
This species is related to the saddleback caterpillar, and shares many of the same characteristics, including food plant (roses). Like the saddleback, the sting is unpleasant but not serious, and can be avoided by wearing gloves when gardening (which you probably will be, since roses are known to have thorns...).
Buck Moth Caterpillar
This is another stinging caterpillar that you might encounter while gardening, although they typically feed on oak trees and not garden plants. Still, they often leave the plant to find a place to pupate, and this is when you can put your hand on one without noticing it.
Buck moth caterpillars pack a very potent sting, comparable to a bee. They can also cause an allergic reaction, so if you're allergic to bee tings you should call the ER if you get stung by this, or any, caterpillar.
For such a menacing caterpillar, the adult buck moth is beautiful, especially some western species.
Cow Killer or Velvet Ant
Cow killers look like gigantic ants – in fact they are also known as "velvet ants." However these fearsome insects are actually a kind of wingless wasp. There are many species, but the most common one are large with red and black bands. They pack a very painful sting, so painful that it gives them their common name – bad enough to kill a cow.
These dangerous insects crawl quickly over the ground in search of prey; I have also seen them on walls. The cannot jump or fly but they can run quickly and will not back down from a fight, if you had it in mind to try to corner one.
It's my sincere hope that you never tangle with one of these intimidating insects, but if you do, call the ER to make sure you do everything you can to off-set the effects of the sting.
These big, active spiders are not truly dangerous to gardeners, or humans in general, but they are capable of inflicting a bite in self-defense. Wolf spiders are a part of the essential ecology of any yard or garden, so like all of the insects in this guide they should be preserved as best as possible.
Wolf spiders capture and eat flies, bees, wasps, and many other insects.
Black widows and their relatives (some of whom are truly gorgeous creatures) have evolved a venomous bite that protects their species from being preyed upon by other insects and animals. If you or I appear to be a threatening presence to a black widow, she will spend a considerable amount of survival resources to bite the perceived aggressor.
Black widow bites are sometimes very serious, and once in a long while fatal. For the most part, though, these big black spiders with bright red hour-glass markings just want to be left alone. You will find them in a tangled web in a dark corner of your garage or basement, and sometimes outside in sheltered places like stumps.
These tiny little monsters are the immature form of spider mites, which are related to ticks. When you or I walk by their hiding place and brush against the plants they're on, they let go and hop onto our pants leg or socks. After a little crawling around, they find bare skin and bite into the upper layer of skin. Their saliva dissolves the upper layers, and they suck up the fluid. This is their source of food; for us, it creates an intensely itchy spot where the skin has been dissolved.
Ticks have come to be seen as a serious public health issue, thanks to the spread of tick-borne Lyme disease. Deer ticks, the kind of tick that carries the pathogen, are generally only found in forested and weedy areas, the same places hwere you would expect to find deer, the animal that deer ticks are trying to find.
In gardens, deer ticks are less of a concern. However they can be found in any overgrown green area, so it's worth taking precautions. Check yourself for ticks after time in your garden; this means checking yourself for dark brown bugs the size of a pin head on your skin.
If you are outside very much in the South and Southwest, you have almost certainly been in the vicinity of at least one scorpion. They hide under rocks and in crevices – they have a very flat, "collapsible" body – and most species come out at night to prowl around for prey. If you encounter one, it's probably because you lifted a rock or otherwise disturbed their daytime hangout.
Scorpions can really sting, although there is only one kind, the bark scorpion, whose sting can be a medical emergency. They are not particularly fast or aggressive, but will sting in self-defense, like a bee or wasp. If you are stung and you feel anything more than localized pain and numbness, call 911. If a child is stung by any kind of scorpion, call 911 immediately!
This video has more information about the risk of scorpion stings:
These big, handsome beetles are not poisonous and cannot sting (no beetles have stingers). The male stag beetles often have huge mandibles (pincers), which look a little like the horns on a stag deer, hence the common name. These big pincers on the males are all show, though, and used in courtship. The short, strong pincers on the female, however, can deliver a very nasty pinch and sometimes even draw blood. If you come across one of these very cool insects, don't mess with it. These beetles are shy and will not bite unless really provoked into it.
Wheel bugs are large, predacious true bugs in the family Hemiptera. They search for caterpillars and other insects, grab them, and insert their long, sharp "beak" into their victim. Venom flows into the prey, liquifying the insides, and the bug then sucks everything up through its beak.
It's not a pretty process, but insects like the wheel bug help keep a lid on the populations of other insects and caterpillars that might harm your garden. The way that these big bugs might possibly be dangerous to you is if they feel threatened enough to bite you with that long, sharp beak. The result would be akin to a bee sting and not likely too serious, but people have been stung by these insects due to careless handling.
Fire ants, especially the Red Imported Fire Ant (RIFA), have become established throughout the American South. They can be a serious and threatening pest, especially if they build multiple nests in your yard or garden. Anyone who has encountered these fast, aggressive little ants knows that they are not to be messed with. Their nests are often low and inconspicuous and right in the middle of your yard, so stepping or standing on them can happen without you even knowing it. Within a few seconds, though, a swarm of defenders will be on your foot and up your leg, biting as they go.
The bite of these and many other ants involves two steps: a bite to pierce the skin, and a spray of formic acid into the wound. While small, these bites burn like fire, thanks to the acid; eventually a small, itchy blister forms.
If you have fire ants, do not mess around. Call a pest control company and do what you can to get rid of this invasive species – they are not a natural part of your yard's ecosystem, and do damage to other, native species in your garden.
Yellow jackets and other wasps are an ever-present hazard for anyone gardening or working outdoors. Especially in the late summer and early fall, yellow jackets and other wasps become more aggressive as they stock up on food to get the hive through the winter. At this time they may wind up inside your shirt sleeve or trouser leg (this is how I myself have been stung).
There is an interesting way to get rid of a yellow jacket nest in the ground that I used with success. This Youtube video describes the method:
- Scorpions l National Geographic
Meet one of history's great survivors, with ancestors going back hundreds of millions of years. Learn how a scorpion manipulates its metabolism in harsh climes.
- Ticks | CDC
Information on ticks and tickborne disease. Provided by the U.S. Centers for Disease Control and Prevention.
The following resources were used for this guide:
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.