Toxic Bee-Killing Hitchhiker Beetles (I Know, Right?)

I’ve said many times that I’m no entomologist.  I am an invertebrate enthusiast.  I enjoy photographing small things, which means I end up with a lot of images of tiny invertebrates.  Once I have photos, I love to figure out what it is I’ve photographed and how it fits into the incredible complexity of its ecosystem.  The only times I’m ever disappointed by that research is when I can’t find any good information – often because there just isn’t much known about whatever creature I’m looking up.  When I can track down a story, it is always fascinating, and reinforces my sense of wonder about the world.

The latest example of that came last week while I was photographing pasque flowers at the Niobrara Valley Preserve.  I noticed a few bees and other insects hanging around the flowers, but most were too wary to be photographed – with one big exception.  There were several big black beetles with large bulbous abdomens and short wings feeding on pasque flowers.  They were intent enough on feeding that I was able to get a few decent photographs, and promised myself I’d look up the species later.  Before I had a chance to start doing research, former Hubbard Fellow Jasmine Cutter texted me some photos of what looked like the same kind of beetle feeding on pasque flowers up in North Dakota and asked if I knew what they were.  Nope, but I was going to.

An oil beetle feeding on pasque flower at the Niobrara Valley Preserve last week.

After a rare failed attempt to use, I sent photos to a couple friends and James Trager responded quickly with the answer – oil beetle (Meloe sp.), a kind of blister beetle.  Once I started looking for more information, I was shocked that I’d not come across oil beetles before.  Ok, not shocked, exactly, since there are way more great insect stories out there than I’ll ever learn, but still surprised, given the abundance of oil beetle accounts online.  Of those, I particularly recommend Piotr Naskrecki’s The Smaller Majority blog, as well as Adrian Thysse’s Splendour Awaits site.

So, what did I learn? First of all, oil beetles produce the same kind of toxin as all other blister beetles – a compound called cantharidin.  Ingesting only a small amount of cantharidin is toxic to most vertebrates.  While that seems like a great way for an oil beetle to get revenge on anything that eats it, it doesn’t necessarily prevent the big flightless beetle from being attacked and killed in the first place.  Don’t worry – there’s more.  When an oil beetle feels threatened, it can secrete bright yellow hemolymph (the insect equivalent of blood) from its leg joints.  As one does.  That hemolymph contains enough cantharidin that any contact with the skin of potential predators causes painful swelling and blisters.  That, of course, is a pretty good deterrent against predators, as well as any foolhardy humans trying to manhandle an oil beetle.

As a side note, cantharidin has been long recognized by humans as a powerful chemical.  Despite its extreme toxicity, it has actually been used (in very small doses) as an aphrodisiac, starting at least a thousand years ago.  Because of the severe consequences of even a slight overdose, however, there are gruesome stories of hopeful lovers causing very painful deaths to themselves or others.  Cantharidin also has a long and varied history in medicines.  Currently, it is being tested for its effectiveness at treating cancer (as in this recent example).

The wings of oil beetles are much too small carry their weight.

The ability to secrete toxic bright yellow fluid from its leg joints is a pretty good story.  However, that just scratches the surface of the fascinating natural history of oil beetles. Most beetles mature through a process called complete metamorphosis, in which larvae  hatch out of eggs and grow until they pupate and become adults.  The larvae usually look completely different from the adult, and often have a very different lifestyle as well.  Oil beetles, however, go above and beyond by using a process called hypermetamorphosis.

When an oil beetle egg hatches, what crawls out is called a triungulin, a speedy little creature that looks much like a tiny silverfish.  The triungulin cluster together and emit a chemical that mimics the pheromone of female solitary bees (bees that individually make nests and raise young, as opposed to honey bees and other social bee species).  A male bee, upon catching the scent, will descend upon the mass of triungulin and attempt to mate with it (guys are so dumb when they’re horny).  Instead, the triungulin quickly crawl up onto the bee and hold on tight.  They stay with the male bee until it finds a genuine female bee and mates with her, at which time the triungulin scramble aboard the female.

Once onboard the female bee, the triungulin hitchhike back to her nest burrow.  When they arrive, they detach themselves and start eating everything then can find in the nest, including the bee eggs and larvae, along with the food the mother bee provisioned for them.  You can watch an incredible short video of oil beetle triungulin here.  During their time in the host bee’s nest, the triungulin molt into much more traditional grub-like larvae, and eventually pupate and turn into adults.  As adults, oil beetles feed on vegetation – including, apparently, pasque flower blossoms.

You’d never know by looking at its cute face that this oil beetle spent its childhood eating baby bees.

Do you see what I mean about the fascinating lives of invertebrates?  Who would’ve guessed that a bulbous-butt flightless beetle would have such a great story?  Answer: anyone who knows much about invertebrates.  As I write this, I have my booted broken ankle propped up awkwardly on the couch, but I’m already formulating plans for how I’m soon going to (carefully) drag myself out into the prairie to collect more images and stories of tiny little creatures.  Stay tuned.

Photo of the Week – July 1, 2016

I often tell people, “I’m not an insect expert, I’m an insect enthusiast.”  I don’t spend nearly enough time immersed in the vagaries of invertebrate taxonomy and biology to know much more than some interesting trivia about most species.  This week provided a couple great examples of my lack of expertise.

Early in the week, I was at the Niobrara Valley Preserve.  While walking one morning, I noticed a longhorn beetle on a white prairie clover flower.  I felt pretty good about recognizing it as a longhorn beetle, and was even able to remember part of the genus (“Typo something, I think”).  I also noticed a small weevil on the same flower.   “Cool!”

Longhorn beetle (Typocerus confluens or Typocerus octonotatus) and a weevil on white prairie clover (Dalea candida) at The Nature Conservancy’s Niobrara Valley Preserve.

A few steps away, I saw another white prairie clover flower, and sure enough, there was a longhorn beetle on that one too.  And another weevil.  This second longhorn beetle had a different pattern on its back from the first one, so I assumed it was a second species.  “Nice,” I thought, there’s a good example of insect diversity – two different beetle species feeding on the same flower.

Another longhorn beetle on another white prairie clover flower.

A few steps away from that second flower was a third one, and it had a longhorn beetle on it as well.  The third beetle looked different than both the first and the second ones.  (Oh, and there was a weevil on the third flower too.)

A third longhorn beetle.

As I walked away from the white prairie clover patch, I started composing a blog post in my head about insect diversity.  Something about how important it is to have lots of different species within each group of animals so that if one species suffers from a disease or some other malady, there are others that can cover the role it plays in the natural world.  Blah blah blah.

When I got back to WiFi, I emailed my longhorn beetle photos to Ted MacRae (an ACTUAL insect expert) who is generous enough to help me with identification of beetle photos.  (Check out his fantastic blog here.)  I asked him what species these three beetles were so I could name them in my upcoming blog post.  When I got his reply, my blog post idea went out the window.  They weren’t three different species at all – they were all the same one!  (By the way, Ted couldn’t tell for sure from my photos which of two possible species they were.  He said he’d need to see the “last ventral abdominal segment” of each to be sure.)

Now, how is an insect enthusiast supposed to keep up when three beetles of the same species don’t even have the common courtesy to look like each other??   I’m ok with the occasional oddball.  With flowers, for example, it’s not uncommon to see one white flower out of a big patch of purple spiderwort or vervain flowers.  Fine.  Genetics provides a few quirks now and then.  But I only saw three longhorn beetles, and none of them had the same color pattern on their back??  I give up.

Oh, and the weevils?  Don’t even ask.  I don’t know.  They all look the same to my eye, but what does that mean?  They’re probably three different species that just happen to be feeding on the same flower.  That would be about right.  Geesh.

So then yesterday, I was in our Platte River Prairies and noticed a crab spider on a black-eyed Susan flower.  It was a pretty spider (you have to admit that) so I stopped and photographed it.

crab spider
Crab spider on black-eyed Susan flower.  The Nature Conservancy’s Platte River Prairies.

After I photographed the spider, I gave the other flowers nearby a quick look, and sure enough – there were crab spiders on several of those too.  Now, here’s the thing: the other crab spiders might have been different species, or they might not.  I’m not even going to guess.  They had different patterns on their abdomens but were generally the same color.  The first one was much broader, but that’s likely because she’s a female, and that’s how it works with spiders.  The other two might be different species or they could be from different growth stages and the patterns might be different for that reason.  Or, apparently, THEY COULD JUST LOOK DIFFERENT FROM EACH OTHER FOR NO PARTICULAR REASON OTHER THAN TO BE CONFUSING.

crab spider
Another crab spider.  
One more crab spider

I could email photos of the crab spiders to a friend who occasionally identifies them for me, but I’m not going to.  I’m choosing instead to simply admire the aesthetics of these fascinating little creatures, and appreciate some general trivia about crab spiders (for example, their front two sets of legs are extra long for capturing ambushed prey, and some species of crab spiders can change color to match the flower they sit on).  After all, I’m an insect enthusiast, not an insect expert (or a spider expert).  So there.

Photo of the Week – July 30, 2015

During our trip to the Grassland Restoration Network workshop in Minnesota last week, several of us got up early enough to catch sunrise at The Nature Conservancy’s Bluestem Prairie on two beautiful mornings.  I shared a few photos from those outings last week, but thought I’d post a few more today.  I’ve got lots more…it wasn’t hard to find subject matter to photograph!

Leadplant and wildflowers.  TNC Bluestem Prairie, Minnesota.
Leadplant (Amorpha canescens) and other wildflowers abound on The Nature Conservancy’s Bluestem Prairie near Glyndon, Minnesota.
Woundwort (Stachys palustris).
Marsh hedge nettle, aka woundwort (Stachys palustris).
The cool dewy morning allowed me to get pretty close to this resting monarch butterfly...
The cool dewy morning allowed me to get pretty close to this roosting monarch butterfly…
Beetle on Flodman's thistle.  TNC Bluestem Prairie, Minnesota.
This beetle was feeding its way across the top of this Flodman’s thistle (Cirsium flodmanii) – at least I think that’s what I think the thistle species was… it’s always dangerous to guess when I’m far from home.
Common milkweed.  The Nature Conservancy's Bluestem Prairie - Minnesota.
Common milkweed flower buds can be just as attractive as the open flowers…
Bee on milkweed.  TNC Bluestem Prairie, Minnesota.
This bee spent the night on a milkweed leaf and wasn’t quite warm and dry enough to fly off when I spotted it.  If you look carefully, you can see pollinia stuck on two (maybe three?) of its feet.  If you’re not familiar with the fascinating (and unlikely) story of how milkweed is pollinated, you can learn more here.
Purple coneflower (Echinacea angustifolia).  The Nature Conservancy's Bluestem Prairie - Minnesota.
Purple coneflower (Echinacea angustifolia).  This is a species we don’t find very often in the Platte River Prairies (though it’s fairly common nearby) so I always enjoy seeing and photographing it when I can.  As with other “composite” flowers, coneflowers are actually collections (composites) of two kinds of flowers – the ray flowers that look like petals and the disk flowers in the center.  Occasionally, as in this case, a genetic signal gets crossed and ray flower pops up where a disk flower should be.

If you find yourself traveling to or through northwestern Minnesota (just east of Fargo, ND), I encourage you to make the time to visit Bluestem Prairie Scientific and Natural Area.  You can find directions and more information on the site here.  The Nature Conservancy owns about 6,000 acres of prairie there, and their ownership is bolstered by several other tracts of conservation land right next door.  The prairie hosts nesting prairie chickens and beautiful tracts of northern tallgrass prairie.  It’s worth the trip to see it.

A Hole New Mystery to Consider

On my last trip to the Niobrara Valley Preserve, I photographed the bark of wildfire-killed pine trees in warm late day light.  I liked both the patterns and the color and was just trying to make some visually-interesting images.  As I was taking the photos, I saw numerous small holes in the trees but didn’t think much about them.  Holes in dead trees are not really unusual, after all.  Upon looking at the photos later, however, I noticed something intriguing – many of the holes seemed to have a funnel shape, or beveled edge, at the surface of the tree.

Tiny holes in the bark of a standing dead ponderosa pine tree killed by a 2012 wildfire.  The two near the center of the image have a funnel-shaped or beveled edge to them.  The Nature Conservancy’s Niobrara Valley Preserve, Nebraska.

I couldn’t come up with a good explanation for that beveling, so I did what I usually do when I can’t identify something – I sent the photos to people with more expertise and begged for help.  Ted MacRae was kind enough to respond that except for the flared ends, the perfectly round holes might have been created by adult pine sawyers (Monochamus spp.).  James Trager liked my speculation that perhaps something like a woodpecker might have chipped away at the holes, looking for an invertebrate meal, and added nuthatches and chickadees as other options.  But none of us have a good answer.

After hearing back from Ted and James, I looked more closely at other photos from that evening and noticed something else that might or might not be a useful clue.  Not only had the edges of some of the holes been chipped (?) away, but there were similar marks elsewhere on the bark.  I’m not sure if those are related to what happened around the margins of the holes or not.  In the photo below, look at the “pitting” – especially in the top left quarter of the image.

More holes in trees.
More holes in trees, along with tiny chipped or pitted marks, both around the insect(?) holes and elsewhere.

Is some creature (bird?  insect?  microbe?)  chipping away at the tree?  If so, why?  And is that creature chipping away at the edges of holes made by beetles too?  And if so, WHY?  Or, are the beveled edges of the round holes a separate phenomenon from the pitted surface of the bark elsewhere?

I guess it’s good for my brain’s health to ponder mysteries like this, and it’s fun to think through all the possibilities.  On the other hand, it would also be fun to KNOW WHAT THE HECK IS HAPPENING HERE, so if you have good theories – or even better, actual answers – please let me know!

I didn’t measure the holes, so I hesitate to give estimates of their size, but they were really small.  Maybe 3-4 mm across?  I didn’t give that info to Ted (but I should have), and I’m wondering now whether the holes were actually too small for pine sawyer beetles.


Survival of the Fittest?

He was engaging and informative – feeding our tour group piece after piece of the fascinating history of the people and landscape of the Wildcat Hills Landscape.  The first guest speaker on the 2014 Nebraska Natural Legacy Conference Field Trip to the Loess Hills was really fantastic.  But as I was listening to him, I was wandering around the outside of the group with my eyes (as they often are) scanning the ground, looking for something small and interesting.

…And that’s how I found this darkling beetle.  It was plodding steadily along through sparse vegetation with no apparent concern that it was readily visible to any predator passing by.  Before I knew it, I was lying flat on my belly with my camera, photographing this intriguing little creature (while still listening, of course, to the captivating speaker…).

Darkling beetle
Darkling beetle

Thanks to James Trager and Ted MacRae, I can tell you that not only is this a darkling beetle, it is one of about 263 described species of asidine darkling beetles in North America (Coleoptera: Tenebrionidae: Asidini).  I did some reading about asidine darkling beetles and came away with many more questions than answers – which happens every time I research any creature…  My biggest question was this: how do these beetles avoid getting eaten by every predator they encounter?

The beetles in the Asidini tribe are flightless, and supposedly rely on camouflage as a major defense strategy.  I don’t know about you, but this one doesn’t look to me as if it’s particularly well camouflaged, except maybe at night.  The other defense ascribed to asidine darkling beetles is that they resemble another group of darkling beetles that has a chemical defense strategy involving a nasty smelling substance that blisters the skin of humans (and probably other predators).

Mimicry is fine and good, but depends upon potential predators being familiar with the dangerous creature you resemble.  That seems like a long shot, given the number of predators running around – how many have had experience with nasty-smell-emitting darkling beetles?  Regardless, the slow flightless beetle I photographed seemed either supremely confident or blissfully ignorant as it trucked along, fully exposed to the world.  It sure didn’t look like it could outrun a hungry bird or other large predator, and it wasn’t making any obvious effort stay under cover as it moved around in the middle of the day.  Seriously, how the heck is this species still around?

Look, what do I know?  Maybe potential predators are well aware of the existence of the stinky blistering-chemical-emitting critters these asidine darkling beetles look like.  Maybe that awareness doesn’t come from from personal experience but instead is embedded deep in the DNA of those predators.  Doubtful?  Think about all the people you know who are deathly afraid of spiders or snakes, even though they’ve had no personal negative experience with them.

One way or another, there seem to be plenty of asidine darkling beetles lumbering through the world, and they’ve apparently been doing it for thousands of years.  They must be doing something right.  Good for them.

I wish them luck.

Longhorns on the Prairie

One of the great things about prairies – and nature in general – is that there is way more to discover than I’ll ever have time for.  Especially within the world of invertebrates, there is no shortage of species to learn about, and every one of them has a fascinating story.  During the last two weeks, I’ve started paying attention to longhorned flower beetles, a group of species I’d noticed before while looking for bees.  Not surprisingly, once I started really looking at them, I discovered that there are multiple species and that they are much more common than I’d realized.

This longhorned beetle is likely Typocerus confluens, according to Ted MacRae.  There were a couple different (but similar) species around the day I took these photos.
This longhorned beetle is likely Typocerus confluens, according to Ted MacRae, but he said there are others that look enough like it he can’t tell for sure from a photograph.   The Nature Conservancy’s Platte River Prairies, Nebraska.

These beetles belong to the “flower longhorn” group of insects (family Cerambycidae, subfamily Lepturinae).  Adult flower longhorns are largely diurnal (active during the day) and feed upon a wide variety of wildflowers.  When I started looking for information on longhorns, I turned to Ted MacRae, an entomologist and author of the fantastic blog, “Beetles in the Bush“.

Ted helped me identify the species I’d been able to photograph around here, and gave me some good information on what longhorns are all about.  Ted, by the way, has documented at least 229 species and subspecies of longhorn beetles in Missouri.  That information made me feel better about being unable to identify my photographed beetles myself, but also strikingly ignorant about a very diverse group of insects I’d never really noticed before.  (Such is the way it usually goes with insects.)

Ted thought this was probably Typocerus octonotatus, a common Great Plains species of longhorned beetles.
Ted thought this was probably Typocerus octonotatus, a common Great Plains species of longhorned beetles.  You might think it looks just like the T. confluens in the earlier photo, but look more closely at the color pattern…  I know, right?!   Helzer Family Prairie, near Stockham, Nebraska.

Flower longhorn beetles are named for their habit of feeding on wildflowers as adults.  As larvae, on the other hand, most longhorn beetles are wood-borers.  That includes many (most?) members of the Typocerus genus – the genus of beetles I’ve been seeing.  However, Ted says the larvae of many Typocerus species in the Great Plains are actually subterranean root feeders on prairie grasses.  That, of course, seems a much more sensible strategy for insects in landscapes with only widely scattered woodland habitats.

Face on.
A longhorned beetle with a face full of pollen.

Now that I’ve started to pay attention to longhorned flower beetles, I’ll probably never ignore them again.  That’s both a blessing and a curse.  I love learning about new species, but it makes prairie hikes go more slowly because the more species I recognize, the more there is to see.  If this keeps up, it’ll take me all day to walk 100 yards!

Thanks to reading this post, your mind has also been infected with the visual image of longhorn flower beetles.  The next time you walk through a prairie, you’ll likely spot more than one.  (You might want to budget just a little more time for that prairie walk, by the way – sorry about that!)

Frozen Bugs (and Beetles)

My family and I spent some time exploring the frozen pond/wetland at our prairie during the holiday break.  We even got a couple days of great ice skating weather.

My three kids had a great time ice skating on the pond over the holidays.
My kids had a great time ice skating on the pond over the holidays.

While we were on the ice, we found some great patterns (see earlier post), but we also found quite a few frozen insects.  In particular, there seemed to be two species of insects – one bug and one beetle – encased in ice.  The bug was a species of Corixidae, or water boatman.  Its name comes from the fact that two of its legs are extra long and sport hairs that make the legs look and function like the oars on a boat.  Water boatmen suck the juices from algae and plants through their long straw-like beak and are common inhabitants of just about any freshwater body around here.  They are also frequently seen in the ice when those water bodies freeze up in the winter.  Apparently, water boatmen can survive freezing and just start swimming again when the ice thaws.  A pretty neat trick for an aquatic bug that lives in a temperate climate.

A frozen water boatman
A frozen water boatman


Another one
Another one

We had a two day period over the holidays during which the temperature briefly climbed up to about 60 degrees (Fahrenheit).  The warmth didn’t last long enough to spell an end to our ice skating, but did melt some of ice along the edges of the pond.  Apparently, the warm temperatures also encouraged a number of individuals of one particular beetle species to go exploring.  Unfortunately, it appears quite a few of those beetles wandered out onto the ice and didn’t make it back.  We didn’t see any of them on the ice before the warm spell, but found lots of them afterward.

Here's one of the beetles that froze after (apparently) getting caught out on the ice after a warm day.  I'm hoping one of my entomologically-inclined friends can help me out with identification and/or natural history info?
Here’s one of the beetles that froze after (apparently) getting caught out on the ice after a warm day. I’m hoping one of my entomologically-inclined friends can help me out with identification and/or natural history info?


This beetle apparently got flipped over before freezing.
This beetle apparently got flipped over before freezing.

I was curious to know whether those frozen beetles could do the same thaw-out-and-re-energize trick as the water boatmen, so I broke off a chunk of ice containing a frozen beetle and brought it home to thaw it.  The beetle has been thawed out for more than a week now, and hasn’t moved, so I’m pretty sure it’s dead…  The next question is: where were those beetles staying during the very cold weather earlier this winter, and how did they prevent themselves from freezing to death then?

Always more questions…

For more information on how water boatmen and other creatures weather the winter, see this earlier post from 2011.