Deer Keds: Blood Thirsty Bugs

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- Hi, Sanford Smith here with Penn State Extension.

Today I'm joined by Michael Skvarla, and if you recall, a year ago, we did a video on Asian jumping worms.

Well, today we're gonna talk about another interesting creature called deer keds.

Michael, what are deer keds and what's interesting about them?

- Deer keds are biting flies.

They mass emerge in the fall and they look for hosts.

Typically, that's a deer, but that can also be something like a human or a dog, and they'll land on that host and bite and blood feed.

So you can think of them kind of like a horse fly or a deer fly, although those are unrelated groups.

- Hunters go out, sometimes they harvest a deer, and all of a sudden they encounter deer keds, don't they?

- [Michael] Yes, so once deer keds land on a host, they'll shed their wings so they can't fly anymore.

And if you go and harvest a deer that is covered in deer keds, you'll find them crawling around, especially if you're in, say, northern Pennsylvania, where they're more common and abundant.

- I remember people saying that they look like ticks.

They were kind of taken aback when they saw all these deer keds running around on a deer.

Tell me about that.

- So, because deer keds shed their wings when they land on a host, they do kind of look like ticks.

They're flattish, they're a little bit bigger than ticks, and they're often much faster.

They scuttle around and can kind of swim through the fur, whereas you think of a tick and they're slow moving.

So you can tell them apart, but they do look similar.

- [Sanford] I've noticed, Michael, that oftentimes you see them in the fall.

Is that when they're most commonly seen?

- [Michael] So deer keds here in Pennsylvania, the species that we have here only comes out in the fall.

They mass emerge over the period of about six weeks, starting in mid-September through about the end of October.

- And they emerge from the forest floor, is that right?

- So adult keds are on deer.

They live on those deer, they blood feed, and they'll live for up to or maybe over a year.

They lay fully grown larvae that immediately pupate, and those pupae then roll off of the deer and just accumulate in the leaf litter until the next fall when all of them hatch out at the same time.

- [Sanford] They hatch out and then go back onto a host.

- [Michael] And then they'll fly back to a host, yes.

- [Sanford] A host deer, okay.

- [Michael] Or people.

- [Sanford] And then they're there for about a year?

- [Michael] Yes, they can live for up to a year at least on host.

- Interesting.

So hunters only encounter them when they get close up and personal with a deer, but otherwise they're not really gonna see too many of them.

- If you're archery hunting, you may encounter flying deer keds in the early fall, but once kind of the end of October rolls around, if you're hunting in November, December, the only place you'll see them is on deer.

- Let's talk about hunters.

Oftentimes they encounter a deer ked and they think, oh, maybe it can have a disease, I can get something from it just like I can from a deer tick or a blacklegged tick.

So can you catch anything from deer keds?

- So there have been a number of studies that have looked at DNA in deer keds and found various tick-borne diseases, particularly Anaplasma and Bartonella.

But there have been no studies that have shown that they can transmit those diseases.

That's not to say that they can't, we just don't know if they can or they cannot because the studies haven't been done.

So for now, we're not sure what the risk is because we just don't know.

- Repellents.

Can you use any kind of repellent to get rid of these deer keds?

- Unfortunately, we did a study a couple years ago and it's just being published now.

None of the repellents, including deet and oil of lemon eucalyptus, none of the common repellents that you can buy at the store were effective against deer keds.

They didn't care at all.

That said, permethrin did kill them quickly.

Deer keds that encountered permethrin treated clothing died within 15 to 30 minutes.

So while it doesn't repel them, it does kill them if they get on you.

- One thing I understand about them is they're attracted to movement, right?

So it's not like they smell a person or can kind of detect a person, but they actually see movement of the deer or a person to fly towards.

- Yes, and that's why we think the repellents don't work.

You think about something like a mosquito or some ticks that you're using, say, deet on, the repellents really mess with their olfaction, their ability to smell, because they're cuing into chemicals that you emit.

Because deer headss are cuing into movement and not smells, that's probably the reason that they don't care about the repellents.

- Yeah, that's interesting.

Okay, well thank you very much, Michael.

- Thanks for having me on. - It's been interesting, and we know a little bit more about deer keds and useful information.

Thank you very much for listening.