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Sierra wormlion - Vermileo comstocki

Sierra wormlion - Vermileo comstocki
Mariposa County, California, USA
June 8, 2017
Size: ~1 cm
Just a weird maggot right?! Wrong! This is one of the coolest insects I've encountered: the mythical wormlion. These strange beasts have evolved pit-digging behavior, an instance of convergent evolution with antlions!

I've now found them in two locations, both on rocky slopes at 7720 ft and 3700 ft in the Sierra Nevadas. Species ID based on range. Both times I encountered them under the ledges of small boulders, presumably providing shelter from rain, in very fine soil. Although seemingly rare/uncommon, I suspect they may not be too difficult to find if you know what you're looking for.

In both cases, the pits were clustered in groups of 5-10, and were quite small - smaller than most antlion pits. I did not notice any very obvious differences in shape from antlion pits, although they may be steeper and subtly more cylindrical at the bottom (as mentioned in Charley Eiseman's Insect Tracks and Signs). The best way to distinguish them from antlions is to simply drop an ant in and observe. Wormlions thrash about wildly as they try to capture their prey, and you'll be able to see their distinctive worm-like bodies.

Upon removing them from the soil, these wormlions assumed a horseshoe-like shape and seemed to play dead. If poked, they'd either continue to play dead or start squirming and jump around energetically.

Fascinating creatures. I captured a few and am trying to raise them to adulthood - stay tuned!

Images of this individual: tag all
Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki Sierra wormlion - Vermileo comstocki

Great series!
Nice photos, and interesting commentary. Like the way you transitioned from large-scale habitat to isolated larva. The habitat image and comments on the rock ledge niche are helpful for giving an idea of how to scope out habitat. Also interesting to see that wormlions will construct pits on fairly sloped substrate.

I have to say, I can't tell which end of the larva the head is on! Even seeing the larva in the context of the burrow (i.e. in the 8th image)...I can't tell from the still images whether it's entering (i.e. head at pointed end), or exiting (head at thickened end). Since it doesn't look like the burrow is in a pit, I'm guessing it was entering the hole (i.e. trying to escape from view of the large hominid nearby). I'm also wondering if the internal black blob at the "thick end" may be a partially digested prey item?

I viewed Charley's fascinating YouTube video of a wormlion capturing an ant, and read with interest his comment there about the distinction between the broad-based burrow of an wormlion vs. the pointed conical-shaped burrow of an antlion. It does seem to apply in at least some instances (see info page thumbnails). The rotating motion of a length of the wormlion larva during prey capture...versus the in-and-out jack-in-the-box movement of an antlion...presumably accounts for the more hemisperical shape of the pit. Of course, like nearly everything in biology, such a general characterization will only hold on average, and not absolutely.

Looks like the Red fir zone, so guess your at the higher 7720 ft location...though I'm still curious as to a bit finer fix on where this is in Mariposa County? If you're still in the area, adults may be out about now. (If you see some, try to get shots showing color of their palpi for Martin :-)

It's great BugGuide posts like yours are starting to accumulate...they're extending the fairly meager distribution records for Vermileo given in the literature (e.g there are none from Mariposa County).

Postscript: Just learned from Joyce Gross that Wheeler's 1930 book "Demons of the Dust" mentions collections from I was likely in error above about Vermileo not being recorded from Mariposa County. Wheeler also mentions that the "dark contents of the stomach" are visible at the posterior end through the "pale grayish pink or flesh-colored" it seems I guessed correctly about the head and tail ends :-)

Thanks for the comment Aaron!
Here's a little more location info: I found them near the intersection of Buenavista and Illilouette Creeks in Yosemite. Interesting that more people are starting to find them right now! I just uploaded have photos of an adult:

I've now found them in two more locations in the park: on the Yosemite Falls trail in Yosemite Valley, in the first mile or so, and at Rancheria Falls (Tuolumne County). And nice tree IDing from a poor photo!: these larvae are indeed the ones found at 7720 feet (a few western white pines were around as well).

Distinguishing the burrows by shape is difficult for me, but I
do believe that it applies. The first thing I look for is groups of small pits, especially under the ledges of boulders (they could very well be elsewhere, though, and that's just where I'm finding them), and in very fine soil.

And you are correct on the head vs tail end! They are fast, headfirst burrowers. I hadn't noticed the prey item at the posterior. Fascinating!

(By the way, I've greatly enjoyed all your plant photos on CalFlora! Great contributions)!

Three locales in Yosemite
Good going Graham! It's surprising one of your sightings of this little known and recorded oddity was along the Yosemite Falls trail...where 1000's of people walk by each year!
As Martin and you have indicated, seems they're more widespread and less uncommon than the literature might suggest. (Although it turns out Wheeler's 1930 book "Demons of the Dust" makes numerous references to stations in Yosemite.)

Regarding the larvae, the MND(1) has a description of them...I added some remarks to the info page(2) from that source.

awesome.... glad you found th
awesome.... glad you found them... I also think that they might be very widespread and not uncommon, although they are rarely collected. Great observation, good luck with the rearing, not too difficult from my experience in the past..

You were right - not too difficult!
Fed on a diet mostly of ants, with some termites too:

Interesting critter and narrative, Graham.
Thanks for posting.

Glad to share!
And I recently encountered them on the Yosemite Falls trail as well. Pretty fun creatures.

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