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