Sunburst Diving Beetle

Sunburst Diving Beetle (Thermonectus marmoratus)

Sunburst Diving Beetle
A Sunburst Diving Beetle (Thermonectus marmoratus) in captivity at the Butterfly Pavilion, Westminster, Colorado, USA. November 10, 2012.

This last month has been very busy for me (partly due to my awesome entomology class), so here’s a quick interlude before I return to the Iceland photos. Today I stopped by the Butterfly Pavilion in Westminster, Colorado, to see the newly remodeled Crawl-A-See-Em exhibit. The Butterfly Pavilion, in addition to butterflies, also exhibits many other invertebrates, ranging from ocean invertebrates like lobsters and jellies to terrestrial invertebrates like bees and probably the most famous resident of the Butterfly Pavilion, Rosie the Chilean Rose-haired Tarantula (or rather, an army of Rosies). The Crawl-A-See-Em focuses on terrestrial invertebrates other than butterflies, and I was excited to see the changes.

While the old Crawl-A-See-Em was always a mixture of animals on permanent exhibit and rotating special exhibits according to what the zookeepers were able to collect in the wild or order from dealers, it didn’t really have a coherent theme. Parts of it were habitat-themed; others were taxonomically themed.

The new Crawl-A-See-Em is arranged by habitat type, which I think gives the room a much better flow. While many of the same familiar animals were there, the most exciting change for me was the addition of a tank highlighting aquatic insects, containing Sunburst Diving Beetles (Thermonectus marmoratus) and some fantastic giant water bugs (family Belostomatidae). I’ve never seen either of these species in the wild, and the tank made them easy to observe.

Predaceous diving beetles (family Dytiscidae) are one of my favorite beetle groups. They have several adaptations for their aquatic lifestyle, including fringed hind legs that work something like oars, as well as a physical gill for respiration. In the picture below, you can see an air bubble at the tip of the abdomen, which is the physical gill. Diving beetles have to surface regularly to renew this air bubble.

Sunburst Diving Beetle (Thermonectus marmoratus)

Apparently as larvae they also have eyes with two retinas and two focal planes, effectively functioning as bifocals–the only known example of bifocal vision in insects.

I kind of want some now, although after my ill-fated attempt at dragonfly larva-rearing this fall, I’m not sure I’m ready to attempt to keep an aquarium again.

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10 thoughts on “Sunburst Diving Beetle (Thermonectus marmoratus)”

  1. If you ever DO want to see these in the wild, I can recommend several locations in southern Arizona where you can easily see both! Sunburst diving beetles are my all time favorite aquatic beetles, Aren’t they they most beautiful swimmers? So very elegant!

      1. Excellent! Let me know if you’re thinking of going and where in the state you’ll be and I can likely suggest something within an hour’s drive. There are SO many of the sunburst beetles and giant water bugs there, and I’ve collected extensively all over the southern part of the state where you find them so I know many places you can find them.

    1. I worked there for six months, and I have to admit, the butterflies were nice (especially in winter), but not even in my top 5 favorite residents. Although my favorite animal, the Caribbean spiny lobster, apparently outgrew his/her tank and has been transferred to the Denver aquarium, so I sense another field trip in my future….

      1. I can see why the butterflies might not have been that exciting compared to other things. I find butterflies pretty, but rather uninteresting behaviorally, so I usually seek out the more interesting species instead. The Pavillion has a good mix of both I think. I’m a little envious you got to work there… They started building it about 2 months after I decided I wanted to be an entomologist, so it was the first exhibit of that type I ever went to. It holds a special place in my heart! (Man, now I’m missing Colorado…)

      2. Butterflies are pretty, but mostly they…fluttered around and ate, and sometimes mated. Not a ton of variety, so aside from getting a new species in, after a while I got a little jaded. But butterflies are an excellent gateway insect, since a lot of people who are otherwise iffy about insects can deal with butterflies, and of course the kids loved them, except for the subgroup of toddlers who thought they were terrifying. (I think Rosie the tarantula, the beehive, and sea stars were probably the most popular with the kids, although it’s been a while, so I’m not sure I remember the results of my informal favorite animal poll anymore…)

  2. I have been researching the sunburst diving beetle and would love to own some of my own, but i am having trouble finding a place to purchase them, is there an obvious reason for this (illegal, will die in over night delivery, etc…)?

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