Friday, April 19, 2013

Cacti ain't so tough...

If it weren’t for a pile of caterpillar poop (“frass” if you want to be fancy), I never would have found myself cutting open a prickly pear pad (and by "myself", I mean watching my lovely wife cut open a prickly pear pad as I became distracted by some large ants), nor would I have learned about cactus-boring caterpillars.
Prickly Pear, Opuntia sp., is a common sight in southwest Kansas.
There I was, minding my own business, walking around a dried up lake adjacent to some remnant sand-sage prairie that is officially “not open to the public”, hoping to reap the benefits of some remnant sand-sage prairie edge effects, when I noticed a pile of frass on a prickly pear pad.
Yes, it does look like something pooped on some Prickly Pear, 'cause that is insect poop.
I’ve seen caterpillar poop in many places before, but never on prickly pear.  Of course, this warranted further investigation.  After finding a stick sturdy enough to compliment the small blade of a pocket knife, the suspect pad was opened.
I can't imagine being interrupted mid cacti-binge.
The culprits were quickly revealed.  Gray-ish blue, black-spotted larvae enjoying the dickens out of some prickly pear pads.
Prickly Pear so good this caterpillar could not be bothered to acknowledge the camera.
May I introduce to you the North American cactus borer, Melitara sp.(a boring brown moth).  Of course, we now have these larvae housed with fresh prickly pear pads at our home.  I mean, don’t YOU want to know which species of cactus borer this is?
By the way, cactophillic insects can be quite effective.  Another cactus borer, the South American cactus borer, Cactoblastis cactorum (that is the best name on Earth), helped eliminate millions of acres of invasive prickly pear in Australia in the 1920’s and later it was used in South Africa and even Hawaii.  That same moth is now invasive in North America, so keep an eye out for any bright orange caterpillars you see in prickly pears.  For more information on that invader, see HERE.

Otherwise, go find some cacti to look at too closely!

Wednesday, April 17, 2013

Big Flippin' Ants!

Here in southwest Kansas it has been hard to miss the large, pebble-covered mounds of the harvester ant, Pogonomyrmex spp., or "Pogos".  These impressive ant mounds can be up to 1 meter (3.3 feet) wide and extend up to 3 meters (10 feet!)  into the earth.   
Damn my lack of scale!  This P. barbatus mound was 3 feet in diameter.
Again, lack of scale, but this P. occidentalis nest was quite noticeable from 100 feet away.
 Naturally, once I found myself standing over one of these mounds in awe, it was also hard to miss the large, red ants busily moving in and out of the mound.   
The Red Harvester (P. barbatus) hard at work.
More P. barbatus, apparently a darker form, ignoring my camera.
 There are 22 species of harvester ant in North America and 6 of these can be found in Kansas.  While it can be tricky to determine exactly what species of harvester ant you are looking at, there are a handful of characteristics (aside from the obnoxiously large mound) that can help you determine that you are definitely looking at a harvester ant.
  1. Harvester ants are noticeably large for ants, 5-10 mm (.2-.4 in)
  2. The commonly encountered harvester ants are dark, rusty red or red
  3. Harvester ants have large heads and formidable looking jaws
  4. If you look a little closer, you’ll notice that the ant’s abdomen is joined to the thorax by a noticeable “stalk” consisting of two segments.
  5. Before the two segments of the “stalk” start, there is a pair of bad-ass spikes!

See? Not so hard.  While these ants are large and intimidating, luckily they are not overly aggressive (at least in my experience so far).  However, the sting of the harvester ant can be quite painful, the venom affects the lymph system and lasts a long time.  Apparently harvesters are responsible for killing at least three small children in Oklahoma.  
"Dude, have you seen the pair of bad-ass spikes on my epinotum?"   "Yeah.  Hey, who's that jackass with the camera?"
 So why are these ants known as “Harvester” ants and not “large, intimidating, kill-you red/rusty-red ants”?  Well, that’s easy.  Harvesters primarily feed on the seeds of various grasses.  Ants actively forage, or harvest, grass seed and store them back at the nest.  Harvester ants also tend to clear away, or harvest, all vegetation surrounding their mounds, sometimes creating a mound clearing up to 7 meters (22.9 feet!) in diameter.  Additionally, I had my face/camera nary .3 meters (12 inches) from these ants the entire time I watched them bounce the weevil from “Club Pogo”.  I am unscathed.  I could not say the same thing if I had been .3 meters (12 inches) from a fire ant mound…more likely I would just be saying, “son of a B$%#&@!!!”.  To further support the idea that these ants are not overly aggressive and are quite content to chow down on grass seeds, a quick story. 
Once upon a time, the author (that’s me!) came upon a visible commotion at the entrance of a harvester mound.  Upon closer inspection, a few harvesters were observed to be grappling with a weevil a bit larger than any of the ants.  Surprisingly, the ants were not trying to drag the weevil into the dark depths of the mound, they were actually trying to eject the weevil from the mound itself.   The ants carried the stubborn weevil about ten inches from the mound opening and dropped it.   Immediately, the weevil scurried back to the opening and again was forced out by the ants.  The weevil did not attempt a third entrance into the mound but wandered off completely unscathed while the ants went back to the business of their harvest.  One (as in me) may wonder (repeatedly) if the weevil was interested in the ants' stored seed or if it was just trying to escape the sun.  Anyways, the ants and weevil lived happily ever after.
P. barbatus bouncers escort Scaphomorphus frontalis from "Club Pogo".
Scaphomorphus frontalis don't care.  Scaphomorphus frontalis has other things to do anyways.
  Go look at some ants!