Thursday, August 11, 2022

The Ant that Ain't - Cow Killer

Our unpaid staff photographer Ben Caruthers sent me a set of photographs of a velvet ant that are too good to pass up. I updated this blog from 2013, guesssing that you won't remember it.

Female Velvet Ant
Some years ago I was out with some young naturalists.  All kids are naturalists if given a little freedom and encouragement.  They found this critter running rapidly through the cropped grass and weeds by our swimming hole.  The consensus among my young naturalists was "Wow, look at that ant!" and they were partially correct.  It is a velvet ant, an insect that "ain't really an ant."  I chased this swift creature for several minutes before catching in it a bug box.  Due to its formidable appearance,  I wasn't tempted to pick it up, a wise decision.

Male Velvet Ant - Ben Caruthers

This is a wasp called an Eastern velvet ant, Dasymutilla occidentalis. Although he looks wicked, he lacks a stinger as do all male wasps.  As a rule of thumb, I assume that all wasps are female until proven otherwise.  In this case however, the females lack wings and don't even look wasp like.

Male side view - BC

Velvet ants are characterized by their dense hair in vivid shades of red, orange or yellow.  The winged males have a different coloration than the wingless females.  Bright colors in insects are frequently warnings of toxicity or the ability to hurt predators like us.  Other harmless insects may also have these bright colors called aposematic that falsely warn of their toxicity.  In this case, the females are the real thing.

"I am not smiling!" - BC

Their other name is "cow-killer" which probably gives you a hint of their defense.  The name derives from the female's stinger.  She has a sting that is rated as a three on a one through four Schmidt sting pain index scale.  Justin Schmidt prompted insects to sting him and then graded the severity of the pain in terms generally reserved for a wine connoisseur.  These ranged from "light, ephemeral, almost fruity" to ""hot and smoky, almost irreverent. Imagine W. C. Fields extinguishing a cigar on your tongue."

Adults feed on nectar and water.  The male flies around looking for females on the ground.  They are parasitoids, rearing their young in nests of other species, eventually killing them.  When they emerge, the males fly off while the females crawl away as a warm and fuzzy "ant" - well maybe not so warm.

"Male mutillids fly in search of females; after mating, the female enters a host insects nest, typically a ground nesting bee or wasp burrow, and deposits one egg near each larva or pupa.  The mutillid larvae then develop as idiobiont ectoparasitoids, eventually killing their immobile larva/pupal hosts within a week or two."  Wikipedia

Surprisingly, the female's toxin isn't all that strong.  The severe pain is due to the extraordinarily long stinger!  Even without a stinger, the wasps have other defenses against predators.  In addition to its coloration and a thickened exoskeleton, when bothered they emit a stinky chemical secretion.  Also both males and females run fast which Ben mentioned makes them hard to photograph, let alone catch.  When threatened, they make warning sounds and clicks by rubbing their body parts together, a trait called stridulation.

Best to remember that their attitude is "just leave me alone!"

 "You wanna pick me up?"  Wayne Boo at  USGS

Monday, August 8, 2022

Frog-biting Midge


 Exciting News - Hang on for a long ride!

This little lady above was collected by our friend and stream researcher Nathan Dorff from Peckout Hollow just beyond our old barn.  After several years collaborating with experts in the field, it is now official.  This is a new species of frog-biting midge, now officially named Corethella kipferi.  These midge larvae spend their entire lives in the hyporheic zone, the water flowing out of sight under gravel bars.  There they happily spend their hours munching on mosquito larvae and other tiny delectables.  Then in a moment of passion they come flying when the female hears the call of a frog and draws out some blood, necessary to produce fertilized eggs for the next generation.

Adult female midges, < 2mm

The female adult specimens above are in my collection.  Preserved in alcohol, they measure just about 2 mm.  Nathan collected them in an insect trap as they were responding to the recorded call of a gray tree frog, Dryophytes versicolor, aka Hyla versicolor.  He had previously collected the larvae from pipe wells he had driven into the hyporheic zone bed of Peckout Hollow running below the dry surface gravel.  You may recall Hyla versicolor from this previous blog.

By now you are probably really confused.  I will try to explain a little more about our new species or you can just read Nathan's whole paper here.

If you are still with me, here we go.  Don't say I didn't warn you!  (Editors note:There will not be a test.)

The frog-biting midges are in the single genus Corethrella.  There were a total of 115 species and counting at last report with "52 of these being new" before Nathan's report.  All known species occur between the 50 North and 50 South parallels and are restricted to areas where frogs can live.

C. kipferi larva - Nathan Dorff
C. kipferi - Nathan Dorff

The larvae of FB midges are not distinctive and cannot be identified down to species level.  That said, I think that think you will agree that they are kinda cute!

FB midge eating mosquito larva - Sturgis McKeever at Bugwood

The larvae are predators on zooplankton in the water, such as mosquito larva above.  They remain anchored and stationary, grabbing dinner as it passes.  There is little known about their dietary specifics although one paper reported a common species that prefers munching on our Asian tiger mosquito larvae.

Of course their fame comes from the female's obligatory diet of frog blood.  They are thought to seek out the frog calls by their specialized Johnston's organ, a collection of sensory cells found on the second antenna segment.  Now that has to be tiny on a 2mm midge!  An article on Eavesdropping Vampires delves deep into how and possibly why they pick out hosts by their calls.

There is even some evidence of some having not only specific host frog species but even preferred biting sites on the frog by different midges such as face sucking or back biting!

Wikipedia CC



Congratulations for hanging on for the whole ride.  This was a lot more than you asked for but I find it fascinating how much we can now learn about a tiny insect that measures 1/16"!

C. kipferi - Nathan Dorff

Finally, I was curious about this face shot and asked Nathan about it. 

"They are photomicrographs….but I’m afraid the techniques are beyond me. Essentially they take a stack of photographs through a microscope from different “depths” at high magnification and combine them to make those spectacular composites with so much detail. Love the compound eyes!!

We are grateful for Nathan's studies, his friendship and sharing his youngest addition to the family with us.