An Introduction to Chiggers

Chiggers and Chigger Bites

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Scanning Electron Microscope image of a yellow mite (Photo: USDA.gov)

What Exactly Are Chiggers?

I have a lot of requests to cover topics about biting and stinging things, mostly because these are the critters that make people's experiences outdoors unpleasant. One such creature is the dreaded chigger. Now most of us have heard of them, and many of us have had their bites, but what are they really? What do chigger bites look like? Should you be worried? Let's start with chigger 101:

What is a chigger?

Chiggers are not insects. They area a member of the mite family (Trombiculidae), closely akin to spiders or ticks (but they are not actually ticks). The term chigger is somewhat misleading because in common language it means a biting mite of any kind. However, biologically the term chigger is used to name the types of mites that bite and cause skin irritations in their larval stage. There are many mites in the Trombiculidae family and not all have larval chigger stages.  In this article I'm going to reference the most common type of mites in our area, harvest mites, and "chiggers" as their biting larvae. Chigger larvae are found as parasites on mammals, snakes, birds, lizards, turtles, frogs, and some types of grasshoppers.

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Adult dermanyssus mite, notice the 8 legs (Photo: Wiki Commons).

 What do chiggers look like? 

Think of something that looks like a pin cushion with legs, and a pointy snout, then make it really small. In fact, most are so small you can barely see them, nearly 1/4-1/2 a millimeter in size.

michael wonduerli flicker

These are a type of chigger mite that prefer birds (Photo: Michael Wonderli, Flicker Sharing). Notice I'm using the term "chigger" here because these are larval mites (6 legs).

They can be orange, light yellow, dark yellow, or red. The most common type, the harvest chiggers, are bright red. Adults are eight legged, like a spider, and juveniles are 6 legged.

A chigger has four developmental stages: egg, larva, nymph, and adult. Like other insects they molt, or shed their skin, as they grow. Fortunately, mites that turn into chiggers only have ONE larval chigger stage. When they turn into nymphs they enter a quiescent stage called an imagochrysalis (pre-adult...but totally sounds like a Harry Potter spell) before they molt into their harmless adult stage. In the nymph stage they eat small soft-bodied soil organisms and the eggs of those creatures. As adults the mites' only purpose is to reproduce, lay eggs, and expire.

Where do you find chiggers?

Harvest mite females lay their eggs in moist leaf litter, damp soil, and weedy patches. They especially like moist rotting logs and areas with berry briars. The females can lay between 3-8 eggs in a clutch per day, and their round moist eggs are buried close to the ground on wet leaf blades or leaf litter. The larvae hatch in about 7 days and they they crawl around until they find the top of a leaf blade, blade of grass, or fallen log to wait. This is the "chigger" stage, and they are hungry for their first meal. They wait for an animal to pass and then crawl onto the skin of the host. You have to brush by them on vegetation. They can't jump like fleas or spring up to get you (this is why you should always wear protective clothing outdoors).

How do chiggers find you?

Much like mosquitoes, chiggers find you by the carbon dioxide you release. Unless you plan on holding your breath outdoors it's best to stay covered up and avoid brushing up against vegetation where chiggers like to live.

Chigger bites & what causes the welts

First, remember that mites are not spiders and they are not ticks. They have their own unique feeding methods. Unlike ticks that have viciously hooked mouth parts, or mosquitoes that have long piercing straws that stab and jab, chiggers have specialized chelicerae (fancy name for insect mouth parts) that make a tiny hole in the host's skin. Compare the images below and you can see the tick has serrated piercing mouth parts while the mite has a simple snout.

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Juvenile tick proboscis (Photo: dartmoorcam.co.uk)

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Mite mouth parts (Photo: USDA)

The mite's chelicerae are actually pretty weak, this is why they tend to find areas of skin that are thin, like armpits, ankles, crotch, groin, belt area, and the back of knees. They also need something to help "push" against so they can get their mouth parts to pierce the skin (this is also why they're often at waist bands of clothing, cuffs, underwear lines, sock lines, etc).

When a chigger lands on you, it makes for the nearest thin skin and hair follicle (also a thin skin area). Once there it uses its chelicerae to piece the skin. It's not this piercing that causes skin irritation, it's the mite's predilection for human skin soup that makes you itch......cause that's what it makes. The mite injects saliva into the bite/pore, and this saliva has enzymes that break down skin cells and turns them into a soup that the mite can slurp up. Because the mite doesn't have a long drinking straw to suck this slurry up with, it relies on those salivary secretions to do double duty. When the enzymes are breaking down the skin cells they also cause the surrounding skin cells and tissue to harden into a tube of hardened cells called a stylostome (how creepy-cool is that?).

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A chigger feeding on human skin. Note the tube like stylostome (Photo: Wiki Commons).

A chigger can feed for up to 3 days, and the longer it feeds the deeper the chigger's stylosome slurpy straw gets. The puritus (great name for intense skin itching) you feel is because of your body's reaction to the chigger's saliva and the stylostome. Your body's immune system will break down the stylostomes, but depending on how deep they are you may itch for a while.

What do chigger bites look like?

Chigger bites look different on different people, mainly because we all react differently. I know I don't swell much with mosquito bites but my friends swell up like balloons. Here's a pretty common picture of bites:

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Picture of chigger bites (Photo; Webmd.com)

Chigger bites can resemble mosquito bites but they're usually in larger clumps and in places mosquitoes don't frequent as often. They may look like blisters or pimples too. For more information check out Emedicinehealth's website.

Getting rid of chiggers

Now repeat after me, CHIGGERS DO NOT BURROW INTO THE SKIN THEY ONLY SIT ON TOP AND THEN FALL OFF. One of the greatest misconceptions about chiggers is that they burrow in the skin and that you have to somehow suffocate them to get rid of them. Nope, that's not going to help. The best thing you can do if you have chiggers, is to take a nice long warm shower and scrub your skin. Chiggers are very weak invertebrates and will fall off fairly quickly. You can also wash off their human slurpy enzymes in the shower too. Nail polish (an often suggest cure) does nothing to suffocate or kill a chigger that isn't there!

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A common Trombicula mite (Photo: Wiki commons)

If you've gotten into a batch of chiggers be sure to wash your clothes in the hottest water possible as soon as possible. If you bring your clothing into the house you risk the spread of the mites in your home or on your pets. Strip off outside if you can, or in a laundry room, and head straight up for a shower.

To keep chiggers under control you should weed frequently, keep grasses low, and discourage rodents from living in or around your home. Avoid sitting on damp logs and in leaf litter when you're in the woods too.

I'm not a doctor, and there are much more qualified individuals to advise you what to do if you have severe itching and chigger bites. Check out the link above for E-medicine or other online resources. Mostly they suggest over the counter steroid creams, analgesics, and time. Just remember, don't scratch! You can cause major secondary infections if you do.

For an herbal assist you can make a combination of lavender oil and witch hazel to soothe the skin.  Get a small spray bottle, put about 1/2" of lavender oil in it, add witch hazel to fill the bottle and shake.  Spray it on mosquito, wasp and other insect bites. Witch hazel soothes the skin (and is antiseptic), the lavender also soothes but repels bugs too.  A small bottle will fit in your pocket easily.  Washing with pennyroyal soap will help repel insects too.

Chiggers and Pets

Remember I mentioned that chiggers like mammals? Dogs and cats are not immune to chiggers either. This is why you need a good flea and tick preventative if they go outdoors. A good bath is called for if you suspect chiggers, and then get them to the vet just to be sure.

Chiggers can seem like gross and scary wee beasties, but they're an important part of the ecosystem, and during the majority of their life stages they eat soil invertebrates that might otherwise have an impact on our food and forest ecosystems. Take care when you go outside, cover up, wear long pants tucked into socks, long sleeve shirts, and spray down with insect repellent. A little caution goes a long way.

 
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About Infinite Spider

I am currently the Education Program Coordinator at the Smithsonian Environmental Research Center. I have also been a curriculum developer for the Smithsonian Science Education Center and a contract curriculum writer for the Discovery Channel. In my spare time I am a blogger here at "The Infinite Spider" (Infinitespider.com), a science and nature blog for naturalists and outdoor educators. I love rowing crew, birding, hiking, kayaking, and being outdoors. My undergraduate degrees are in Environmental Science and Philosophy, and my graduate degree is in Biology. Currently I live in Annapolis, MD.