Friday, September 7, 2012


I learned something yesterday.

Yesterday something that looked, out of the corner of my eye, like a large clumsy moth/grasshopper careened by us and landed unceremoniously and loudly on a jasmine plant.   I went over to investigate and found a large mantis looking back at me.

I say looking back, because as I moved around it taking pictures, it appeared as though it's eyes were following me.  At least it looked like there was a pupil always aimed me, but I couldn't otherwise figure out how it's eyeball would move, and didn't they have compound eyes?

That is when I learned about the pseudopupil!

"In the compound eye of invertebrates such as insects and crustaceans, the pseudopupil appears as a dark spot which moves across the eye as the animal is rotated. This occurs because the ommatidia which one observes "head-on" (along their optical axes) absorb the incident light, while those to one side reflect it. The pseudopupil therefore reveals which ommatidia are aligned with the axis along which the observer is viewing."

I imagine this effect is just more obvious in the mantis, because of the size and color of their eyes.  And their willingness to hold still.  It did also turn it's head to follow my actions, giving the impression of more presence of mind than most insect encounters.

Another interesting factoid from Wikipedia "All S. Californicas have sensors near their legs that allow the praying mantis to lose its head and still function. This is good if the head is devoured during mating."  So much for presence of mind...

This one maybe the native Stagmomantis californica, California Mantis, but possibly the introduced Mantis religiosa - there seems to be a dark spot on the bicep, but I can't tell for sure.  I think it is a he, based on the length of the wings in comparison to the torso (thank you RandomTruth for the guidance on this and species!).  I hope he hangs around and catches some of the horse flies.



  1. Very nice. They do have a way of looking at you, cool pseudopupil aside. I can't quite see in your pics - does your mantid have a big dark spot on each inner bicep? If so, that likely makes it Mantis religiosa, the non-native Euro Mantis. They're commonly sold in the garden trade and have done well in CA.

    If there's no bicep spots, then it would likely be Stagmomantis. But, I'd say a male - the females have way shorter wings - pretty much 1/2 their abdomen shows. You know, like at the local high schools. ;)

  2. Thanks for the tips RandomTruth! I didn't check when he was here, and none of my photos show a bicep spot for sure. However, there does seem to be the hint of something dark there on the top photo.

  3. Yah, I can't tell for sure if that's a bicep spot either. But other features also do look kinda right for Euro. Here's a Euro from my local park, and a female Cali too, showing the short wings.


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