Avicularia purpurea molt - iridescence on the exoskeleton

I had to look up iridescence, to figure out how to spell it, and I hadn't really thought about the definition, but here it is, via wikipedia:

Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change colour as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, butterfly wings and sea shells, as well as certain minerals.

Apparently another example is the footpads of Avicularia species tarantulas.

I am really grooving on taking shots of post-molt exoskeletons. After all, you have all the time in the world to set up the shot. And I got some nice shots of the iridescence that I have been noticing in certain lights on their foot pads. And I also got a nice shot of those needle-sharp fangs. This molt had being hanging around for quite awhile at the bottom of Arabella's silk home. She seemed to be increasingly bothered by it, avoiding that end of the home, occasionally going down and pushing on it a bit. So today I decided that perhaps she would prefer it gone. Usually tarantulas decide themselves when to kick the molt out.  Most of them seem to keep them for at least a few days, not sure why. Maybe just recovering enough to have the energy to do the job.

Time between molting for different arachnids

Almost since I began keeping arachnids I have been keeping a log of feeding, molting and rehousing of all of my arachnids. Mostly because I have the memory of a mouse, and if I don't keep track I will have no idea who is due for what, and they would all probably starve.  I have noticed, not surprisingly, that as animals get older, the time between molts grows longer.  I thought I would look a little more closely at this to see if I could figure out how to predict the next molt for an individual. Well I haven't gotten that far yet, but I did find an interesting pattern.

In the following graph the green lines represent my four Amblypygi (Tailess whip scorpions), the black lines represent three different species of tarantula, and the red line represents a single true spider, my Tegenaria gigantean (giant European house spider).  Please note, the Y-axis is a bit arbitrary.  Day 1 was simply the first day I started the log (and I got the animals at different points in the log), and the first molt wasn't necessarily the first molt ever for the animal, they may have molted before I got them. The best fit for these lines would not be a straight line, obviously, but just for interest sake I treated them as straight lines and calculated the slope.  The Amblypygi have a slope of between 103 and 185, the tarantulas between 40 and 68, and the true spider at 29.  This means that the number of days between molts for the Amblypygi goes up much more steeply as they age then either the tarantulas or the true spider. I was a bit surprised by the difference between the Amblypygi and the tarantulas, because I thought the slope might be related to the longevity of the animal, but Amblypygi and tarantulas are similarly long lived, and and least some species of tarantulas live longer.  However, Amblypygi molt their entire lives, albeit very seldom as adults.

What is the application of this?  Nothing much that I can think of . . . for now. It would be useful to be able to predict when an animal is due to molt. Usually their behavior gives it away, not feeding, hiding, etc. But sometimes we miss these subtle cues, and a cricket loose with a molting animal can be disastrous. Knowing a range of when an animal is likely to molt could make me more careful about feeding.  Also it's just kind of interesting. Another question I would really like to answer is will stress cause them to delay molting?

Empty Eyes

One of my current longings is for better equipment and the skill to take really great pictures of insects and arachnids. Despite my lack of equipment and skill, I managed to take a picture of an exoskeleton from my newly molted Heteropoda boiei spider using my crappy old camera pressed against the eyepiece of my very small, inexpensive (but surprisingly nice) dissecting microscope. The result was quite decent.  I love the empty eyes left behind when arachnids molt.

Edit:  The next molt I got some more pictures like this, even better ones.

The tailess whip scorpion - Damon diadema, just after molting

I got some decent shots of my tailless whip scorpion, Damon diadema, just after it molted this last time.  They are so incredibly different looking just after a molt.  I like these shots because you can see the old exoskeleton, and get a sense of how the whole process works.  I haven't been lucky enough to catch mine at the beginning of a molt.  There is also an amazing video of one of these guys that shows the entire molt, I highly recommend it, complete with super awesome, weird music.  You can find it here:
https://www.youtube.com/watch?v=5uzuYRY2faQ

I have always wondered, do insects and arachnids that molt have any control over when it happens, or does it simply happen when it happens?  My tarantulas will build complex hammocks to lay in when they molt, so clearly they know it's coming, but can they decide, hey today seems safe, let's do it?  Of course I don't really believe they have a thought process like this, but I still wonder if they have any control at all over when the process begins.

Here are my shots of Critter:

And then there were three

I started out with about 30 mantids. I sold quite a number of them, lost a few to actual deaths (as opposed to a lot of just playing dead).  The number one killer of mantids seems to be molting accidents.  Molting is the process of shedding the exoskeleton so they can grow. This is a really vulnerable time for them, definitely a time when they could be eaten by predators out in the real world.  In my house I lost a few because I just wasn't paying attention when I picked up their containers to feed them, and disturbing a molting mantis will usually result in it falling. Having hit the ground, it's exoskeleton will harden into a position not conducive to continued existence.  Poor Rambo though, so named because he had already survived a number of difficult mantis-life experiences (including three days wandering my house on his own), simply chose a poor location to molt.  He was too near the ground and so as he shed his skin, hanging upside down as they do, he hit the dirt in the bottom of his container before be managed to completely shed his skin.  This mangled his poor head and body, and I put him in the freezer to end his suffering.

Rest in peace (or pieces?) poor Rambo.  Note the old exoskeleton still clinging to the bottom of his body.

The three that are left, Stripey, CrazyPants and No-Name, are living a charmed existence, and are ridiculously entertaining. These tiny cats love to groom themselves and love to sit on people.  As soon as they see me, I swear, they just want out so they can inhabit my person.  They really are keen on people. You wouldn't think an insect brain would even note the existence of people.  Certainly my tarantulas do not consider me to be of the same universe as they are.  But the mantids clearly enjoy my company - see accompanying images!

"I'm so tired from eating that yummy maggot, mind if I just use your hand as a lawn chair for awhile?  By the way, you should clean your fingernails!"

"While I am here, I may as well clean up the maggot-related toe-jam."