A beetle with remarkable eyes

September 25, 2017 • 2:00 pm

Here’s  tw**t found by Matthew Cobb:

Now I’m not sure exactly what a “behemoth beetle” is except a “big beetle” (I can’t find the group), but never mind. Here are its eyes, which don’t go 360 degrees around, but pretty far:


This means that the beetle can see above its head and below it, in other words nearly a complete fisheye view of the world around its head. What it can’t see is a comprehensive and similar view from its head to its tail vertically or horizontally: the median and dorsal planes shown here.

Such an arrangement of the eyes, which is surely a result of natural selection, means that this species has to pay particular attention to what is above and below its head.  Any guesses what’s going on? (Don’t ask me, I just work here.)

13 thoughts on “A beetle with remarkable eyes”

  1. Could it be a case like the flounder, where the eyes have only recently started going around?

    So with this beetle, the eyes are in the process of moving somewhere or expanding…

  2. From above the enemy are birds. From below is where the food is. I might run from this thing.

  3. The upper eye lobes seem to be nearly hemispherical, in which case they likely give a nearly complete view of the entire sky.

    The side lobes should give similar wide-angle views to right and left, though parts of those views are obstructed by the beetle’s own body.

    So my interpretation would not be that the beetle is particularly focused on what’s above and below, but that it has a wide, nearly spherical field of view with blind spots fore and aft.

  5. This is a prionine cerambycid beetle (aka longhorn beetle) all members of the family have a more or less emarginate eye around the base of the antenna. Eyes that cover the whole head (holoptic) are found in many insects and entirely divided (2 eye regions each side) has evolved multiple times in beetles. Gyrinidae (Whirligig beetles) are the most famous example.

    1. As adults, most cerambycids are relatively short-lived — often feeding on flowers [pollen and nectar] or sap flows. Many longhorns seemingly do not feed as adults.

      The typically massive mandibles in cerambycids function most importantly to cut their way out of their pupal cells, often through several cm of solid wood.

      In a few cases, mandibles are sexually dimorphic, the males possessing stag-beetle like jaws. I assume that these are sexually-selected and used in male-to-male jousting.

  7. My impression is that eye shape in cerambycid beetles is a compromise, where long and sometimes massive antennae necessitate unusually large antennal bases [scapes] and their muscular attachments are given priority of place. The large mandibular muscles require attachment area as well. Given those constraints, the ommatidia are painted over areas left over from other organ systems.

    As suggested above, vision in these beetles is good for detecting movement [predator avoidance] over very large angles of incidence. Detecting shapes, not so much.

  8. In order to answer the question, we would need to figure out:
    who the predators are, what these things eat, how they mate, and how their behavior differs from other beetles who do not have such eyes. Or maybe we could do an experiment, we could capture a few hundred of these things, disable(via painting over or removing) different parts of the eyes and see what happens to the beetles. If we cover the top section of the eyes and those ones get eaten by birds, then we know why that trait might have evolved. I doubt we will ever carry out that experiment, but that might be the best way to figure it out.

Comments are closed.