Tetraopes tetrophthalmus

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IMG_2915_RedMilkweedBeetle_600.jpg

Tetraopes tetrophthalmus – red milkweed beetle, Chautauqua Park, Boulder, Colorado. See also small milkweed bug.

20 Comments

Looks like the photo’s been took on a frosty morning.

Marilyn said:

Looks like the photo’s been took on a frosty morning.

The dusty look on the elytra is fine hairs, not frost.

The beetle’s binomial name translates as “four eyes four eyes” - the base of the antenna has been displaced so far into the eye that each eye is split in two, hence “four eyes” - see http://www.cirrusimage.com/beetles_[…]milkweed.htm

Does the genus name Tetraopes refer to the 4 dots on (what I think is) the thorax? I assume that not all species have antennas coming out of their eyes. Is the proximity of the antenna and the eye an adaptation?

Matt Young said:

Does the genus name Tetraopes refer to the 4 dots on (what I think is) the thorax?

It means “four eyes” - the antennas have split the eyes.

It means “four eyes” - the antennas have split the eyes.

I know, but do all members of that genus have split eyes, or only the species T. tetrophthalmus? If it is only the species, then does the generic name derive from the 4 dots?

Matt Young said:

It means “four eyes” - the antennas have split the eyes.

I know, but do all members of that genus have split eyes, or only the species T. tetrophthalmus? If it is only the species, then does the generic name derive from the 4 dots?

“Greek tetra ‘four’ + ops ‘eye’ (in this genus, each compound eye is separated in two)” - http://bugguide.net/node/view/2965

in this genus, each compound eye is separated in two

That, of course, raises the question why only that species is tetrophthalmus, but I won’t ask it.

I wondered whether the split would make it blind or give it four way vision, and if the split was the same on each beetle. I haven’t heard of any thing else having four eyes.

Marilyn said:

I wondered whether the split would make it blind or give it four way vision, and if the split was the same on each beetle. I haven’t heard of any thing else having four eyes.

I forgot spiders do don’t they, so I suppose there will be others.

I’m assuming the beetle’s colours are aposematic and that the beetle itself is toxic, much like the Monarchs that feed on the same plant.

Marilyn said:

I wondered whether the split would make it blind or give it four way vision, and if the split was the same on each beetle. I haven’t heard of any thing else having four eyes.

The four-eyed fish, Genus Anableps, have a bar of iris-tissue that splits the pupil in two: each pupil projects images on two different sections of the retina. The lower pupils scan for potential aquatic predators, while the upper pupils scan for insects and predatory birds.

The brownsnout spookfish, Dolichopteryx longipes, has the retina divided into two chambers, one with the original lens (where the opening points up), and a second, downward-pointing chamber with a large mirror, instead of a lens.

http://en.wikipedia.org/wiki/Brownsnout_spookfish

On the other fin, if Intelligent Design Theory is so much more explanatory, one wonders why the Intelligent Designer not simply give both fishes four separate eyes, rather than go through so much trouble to split their preexisting eyes. Or why Creationists/Intelligent Design proponents have never bothered to divine the Intelligent Designer’s inscrutable motive for doing so, beyond the standard “God is Great”

apokryltaros said:

On the other fin, if Intelligent Design Theory is so much more explanatory, one wonders why the Intelligent Designer not simply give both fishes four separate eyes, rather than go through so much trouble to split their preexisting eyes. Or why Creationists/Intelligent Design proponents have never bothered to divine the Intelligent Designer’s inscrutable motive for doing so, beyond the standard “God is Great”

Well because God works in mysterious ways, clearly.

apokryltaros said: On the other fin, if Intelligent Design Theory is so much more explanatory, one wonders why the Intelligent Designer not simply give both fishes four separate eyes, rather than go through so much trouble to split their preexisting eyes.

They had separate eyes, but Adam’s sin and fall from God’s grace resulted in the split eyes you see in these bugs today.

And remember kiddies, such changes are totally not evolution. And ID theory is totally not religious.

Marilyn said: I wondered whether the split would make it blind or give it four way vision, and if the split was the same on each beetle. I haven’t heard of any thing else having four eyes.

Recall that insects have compound eyes, made up of hundreds to thousands of ommatidia. I would hypothesize that the antennal split has little efect on the beetle’s vision.

Do you think it would be an eye gene and an antenna gene or a combined eye-antenna gene.

Marilyn said:

Do you think it would be an eye gene and an antenna gene or a combined eye-antenna gene.

I think it would be the exact same “eye gene” and the exact same “antennae gene”, with some minor modifications *through random mutations) in the cis regulatory regions of the genes controlling their temporal/spatial expression patterns. Now that’s a testable hypothesis.

Would you think the antenna divides the eye or the eye divides for the antenna — -the base of the antenna has been displaced so far into the eye that each eye is split in two, hence “four eyes”—- this would suggest it starts with one eye and the one eye is divided by the movement of the antenna rather than a definite procedure to create or for there to become four eyes which are of use as with the Brownsnout spookfish. And that there really should only be one eye but the antenna divides it to make two eyes still usable due to —-Recall that insects have compound eyes, made up of hundreds to thousands of ommatidia. I would hypothesize that the antennal split has little efect on the beetle’s vision-.

Yeah, it sounds like just a shift in the location at which cells are triggered to become antennae cells.

That could be either a change in the trigger mechanism (to activate on a slightly different chemical signal) or a change in whatever cells produce the chemicals to which that trigger is sensitive.

(Note- I’m just guessing; an actual biochemist would have more detail.)

Henry

Matt Young said:

in this genus, each compound eye is separated in two

That, of course, raises the question why only that species is tetrophthalmus, but I won’t ask it.

Nitpicking English usage thumb’s up -

Thank you for saying “raises the question” rather than “begs the question”.

http://en.wikipedia.org/wiki/Beggin[…]Modern_usage

Obviously, one could argue that the correct meaning of “begs the question” has shifted, but the whole issue can be avoided by saying “raises” or “implies” the question.

Marilyn said:

I wondered whether the split would make it blind or give it four way vision, and if the split was the same on each beetle. I haven’t heard of any thing else having four eyes.

For the most part (except for crossing our eyes and optical illusions), humans don’t experience “double vision”. We manage to meld our two optical inputs into a single coherent picture of our world. To the extent that insects can also do so, I can’t imagine that displacing some of the optical input elements would have a noticeable effect on their vision.

It does get to the interesting question of how another kind of creature “sees”. The original movie, “The Fly”, showed us multiple tessellated images of the wife screaming. Just imagining being a bird or prey animal with eyes on either side of the head (with essentially 360 degree vision), always seemed kind of strange. But in reality, it’s hard to imagine a nervous system that would not automatically assemble those disparate inputs into a coherent whole. The cognitive power to track multiple images just doesn’t seem to be there.

More explicitly, if the act of splitting the eye would cause the insect confusion about the world around it, natural selection (ie evolution) would quickly weed out such individuals, leaving only those individuals with no confusion about their visual world, either through disabling the nerves to one of the parts of the eye, ignoring the inputs from one of the parts, or successfully integrating all four visual sources.

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This page contains a single entry by Matt Young published on July 9, 2012 12:00 PM.

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