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Fun with antlions: Did you know their pupae can bite?
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MarkSturtevant



Joined: 21 Nov 2015
Posts: 273

PostPosted: Tue Dec 05, 2017 2:11 pm    Post subject: Fun with antlions: Did you know their pupae can bite? Reply with quote

Antlions are insects whose name refers to the predaceous habits of their larva. They belong in the order Neuroptera, and so their relatives include lacewings (whose larvae are called aphid lions). Antlion larvae are famous for digging a conical pit in the sand, and lying in wait at the bottom for an ant or other small insect to tumble in. The action of this pit trap involves some physical principles that are interesting. The pit of sand is stable since the sand grains rest at their ‘angle of repose’. But a displacement of a single sand grain, as would happen if a small insect were to tumble in, would create a tiny avalanche that will draw the insect closer to the waiting jaws below. The antlion will rapidly flick sand out to keep their prey tumbling downward into the jaws of doom.
The following pictures show how I raised a number of antlions to the pupal stage. The larvae were kept in individual cups of sand since if I did not, they will seek each other out and chomp on each other. They were fed ants every day or so, and I had up to a dozen going at one time. First lets look at the antlion housing, the larvae, and a feeding...

One antlion /cup. You can see how messy they are! Note the dead ant carcasses.


A larva.


Close-up. They suck their prey dry with their jaws.


Waiting for prey. They are always hungry.


A strike and a miss!


Got 'em! Note the jaws wrapped around the waist. And...


Pulled under.


Next are the cocoons that they later spin in the sand, and in the cocoons are the pupae. Although the pupae are not predatory, they are pretty exciting since they are still able to bite -- rather fiercely too! This is actually typical of Neuropteran insects, and the pupae of some other insect orders (Mecoptera & Trichoptera). The slightest touch will illicit a strong, bitey reaction from an antlion pupa.

Cocoons.


A pupa. Jaws open...


Chomp!


Antlion adults are strikingly different. Delicate, dainty creatures as shown in the last picture. I think this species may be Brachynemurus abdominalis.

An adult antlion.

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Mark Sturtevant
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Chris S.
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PostPosted: Tue Dec 05, 2017 2:44 pm    Post subject: Reply with quote

Mark,

What a wonderful series! I've often seen ant lion pits in the field, and watched ants fall in to their doom. But your exposition showed me a lot I never knew about their life cycle. Bravo! Very Happy

--Chris S.
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Lou Jost



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Location: Ecuador

PostPosted: Tue Dec 05, 2017 3:14 pm    Post subject: Reply with quote

Great set. I had no idea about the biting pupae! Nice eyes on the adult.
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mawyatt



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PostPosted: Tue Dec 05, 2017 3:58 pm    Post subject: Reply with quote

Mark,

Thanks for the info and images. We are loaded withe these little guys here in Florida, but I didn't know much about them.

As a kid I remember catching them with a spoon, scooping up the sand and watching them wander around in my hand. Then placing them back in the sand and watching them create the little sand trap.

Very clever how the sand cone works and traps the prey.

Best,

Mike
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MarkSturtevant



Joined: 21 Nov 2015
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PostPosted: Tue Dec 05, 2017 4:15 pm    Post subject: Reply with quote

Thanks, people!
I wanted to ask a basic question here, which is how do you post an animated gif movie in this web site? I made an animated gif of the two pictures of the biting pupa, and it plays on my computer just fine. But when I post it here the .gif extension is removed and replaced with .jpg extensions. I don't think that will play the animation. I was looking in the site here and did not see a procedure, though I think some posts had animated gifs.
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Mark Sturtevant
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Deanimator



Joined: 23 Oct 2012
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Location: Rocky River, Ohio, U.S.A.

PostPosted: Tue Dec 05, 2017 4:49 pm    Post subject: Reply with quote

Chris S. wrote:
Mark,

What a wonderful series! I've often seen ant lion pits in the field, and watched ants fall in to their doom. But your exposition showed me a lot I never knew about their life cycle. Bravo! Very Happy

--Chris S.

Where in Ohio are you?

I've never seen antlions in the Cleveland area.

Where would you look?
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Yawns



Joined: 20 Dec 2015
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Location: Portugal

PostPosted: Tue Dec 05, 2017 6:04 pm    Post subject: Reply with quote

I never saw antlions in my life (and I'm 55) but this year .. I would love a picture of one with the wings open , but they seem to keep the wings open only a split second after landing ...

Thank you for this beautiful series and description .. next spring / summer you will see me looking very close to the ground Smile .. I wasn't having any idea about the traps and larvas etc... Thank you.
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Lou Jost



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PostPosted: Tue Dec 05, 2017 7:02 pm    Post subject: Reply with quote

Sandy dry places that are sheltered from the rain are best. Like under a roof overhang or at the feet of sandy overhanging cliffs.
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rjlittlefield
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PostPosted: Tue Dec 05, 2017 7:09 pm    Post subject: Reply with quote

MarkSturtevant wrote:
I wanted to ask a basic question here, which is how do you post an animated gif movie in this web site? I made an animated gif of the two pictures of the biting pupa, and it plays on my computer just fine. But when I post it here the .gif extension is removed and replaced with .jpg extensions. I don't think that will play the animation. I was looking in the site here and did not see a procedure, though I think some posts had animated gifs.

There is no special procedure. You just select a .gif file when the "upload picture" dialog tells you that "Datatypes: jpg, jpeg, pjpeg, gif, png" are acceptable. I've just now made a quick check to be sure there's nothing obvious broken, by uploading an animated .gif using Chrome on Windows. That worked fine.

So, from my standpoint, the interesting question is what procedure did you follow, that made it break? Are you sure the file had a .gif extension when you tried to do the upload? What browser did you use, on what type of computer?

--Rik
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MarkSturtevant



Joined: 21 Nov 2015
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PostPosted: Tue Dec 05, 2017 7:59 pm    Post subject: Reply with quote

The original pictures are jpgs, but I stacked them in Gimp and exported as a gif file. The animated file has a gif extension, and it plays in my computer plus on the web at a different site from here.
MacBook Pro, running Firefox. Let me just try it to see if it works again here. I never actually posted since it was looking like it was converted back to a jpg based on the file string it displayed. One moment...

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Mark Sturtevant
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MarkSturtevant



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PostPosted: Tue Dec 05, 2017 8:01 pm    Post subject: Reply with quote

Well, looks like I broke it. The picture above was two pictures with a gif extension, and it plays. I swear it.
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Mark Sturtevant
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MarkSturtevant



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PostPosted: Tue Dec 05, 2017 8:08 pm    Post subject: Reply with quote

Anyway, to address other comments above: Antlion pits seem to be patchily distributed, but they are found in concentrations in certain environments. Sandy soil in the shade, along the margins of clearings and forest edges. Especially if there are lots of ants. There, they can occur in concentrations. Because of their patchy distribution you can look in the 'right' places and not see any, and suddenly come across dozens of pits.

I bet the larvae would be spectacular in a stacked image. They do move around, but will also sit still for extended periods.
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rjlittlefield
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PostPosted: Tue Dec 05, 2017 8:40 pm    Post subject: Reply with quote

MarkSturtevant wrote:
Well, looks like I broke it. The picture above was two pictures with a gif extension, and it plays. I swear it.

OK, got it. I'm guessing the problem is that the .gif you uploaded was larger than 1024 pixels. That caused it to be automatically downsized, and I've just now confirmed that the forum's downsizing procedure converts .gif to .jpg . The file that you uploaded was undoubtedly way over the 300 KB file size limit also, but that didn't matter in this case because the resize for pixel count takes precedence. The result was "two wrongs makes a weird", which I'm very proud to say is a phrase that Google does not recognize.

In general, you never want to let the forum software resize an image for you. There will always be significant loss of sharpness, compared to what you can get if you do the resizing yourself.

So, to post an animated .gif, here is a more detailed procedure:

1. Resize your image so that the saved .gif file is no bigger than 300 KB in length, and no larger than 1024 pixels in either dimension. For a two-frame .gif, the 300 KB limit means that your image can only have about 150,000 pixels, roughly 300x450.

2. Be sure that the file name ends in .gif .

3. Upload the resulting .gif using the normal "Upload picture" button.

Please try it that way and see what happens.

--Rik
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MarkSturtevant



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PostPosted: Tue Dec 05, 2017 9:14 pm    Post subject: Reply with quote

Thank you for your help! Reducing the two frames to 1024 still makes the whole file about twice the size of the limit, so I reduced the frames a lot more, to where the full size is just a little below the size limit. Lets try it now.

I see in the file string that the .gif extension is retained.

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Mark Sturtevant
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MarkSturtevant



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PostPosted: Tue Dec 05, 2017 9:20 pm    Post subject: Reply with quote

The largest dimension of the pictures was 650px, and the total file size reads 296kb. It has the .gif extension and it plays for me.
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