Tuesday, July 13, 2010

Tiger Beetle Behavior

If this was a low budget science fiction film, this is where Monster B would take down Monster A, but this is actually a friendly encounter. In my quest to discover the various species of Tiger Beetles living at Blue Jay Barrens, I have had opportunity to observe quite a bit of Tiger Beetle behavior. The most frequently viewed subject has been the Eastern Red-Bellied Tiger Beetle, Cicindella rufiventris, a beetle that I now refer to as Rufe.

Tiger Beetles spend a considerable amount of time hunting. They tend to position themselves where they can scan the surrounding bare area for small prey items. In areas of rougher ground, it’s not uncommon to see them perch atop slight rises in the landscape. This individual kept shifting from what, on the scale of a small beetle, would have been ridge top to ridge top.

I haven’t identified the exact prey being captured, but it is something small. The two most common things I see moving through the area are small ants and spiders. Once the prey is subdued, the mandibles seem to be held apart while the morsel is chewed and swallowed. The beetles also seem to crouch while feeding, somewhat like a dog guarding a bone.

As the day heats up, the beetles seek shade. I’ve seen several dart from a shady spot, make a capture and then run on to the next shady spot to consume the meal. Judging from the heat I felt while taking photographs, the ground must be scorching. Most insects have an optimal temperature in which they best function and one of the ways of regulating that temperature is balancing exposure to shade and sun.

I watched this particular female for quite some time. She was hunting a patch of ground in the shade of a cedar tree, so exposure to direct sunlight was not an issue. She was capturing tiny insects on a regular basis.

Suddenly a male rushed over and hit her with what resembled a flying tackle. She seemed oblivious to the whole encounter. He held on with his front legs as he got himself positioned.

Within seconds he anchored himself with his mandibles firmly grasping a point just ahead of the elytra. Once secured and mating commenced, he threw his front legs wide, looking much like a rodeo rider coming out of the chute. From there he just followed the female wherever she chose to go, using his second and third pairs of legs to keep pace. I would guess this position gives the female unencumbered mobility should the need for speed arise.

I suspect the female’s contours match the form of the male’s mandibles so a tight lock can be achieved. This key and lock type of anatomy is common in some species and is a guard against the male of another species mating with the female. A male that didn’t fit the mold could more easily be dislodged. Her behavior hardly changed during mating. While coupled, she nabbed two more little somethings running across the soil.

After a couple of minutes, the male uncoupled and ran off. It’s possible I scared him while repositioning for shots from a different angle. She went right back to hunting, as though nothing had happened. I’ve purchased a Tiger Beetle book and will be reading up on this fascinating insect. With any new subject, I like to look first and then read to see if the text explains what I’ve been seeing. I seem to get a lot more out of the book that way.


  1. Yes, the first image could be a low-budget monster movie. You may be getting calls from a producer soon.

    Seriously, I enjoy your blog and learn something new every time I visit. Welcome and thank you for visiting my blog, too.


  2. Excellent photos and writeup on your behavioral observations. You seem to be spot on with your interpretations - good job.

    I'm not sure how much of a "lock and key" mechanism the mandibles/mandibular groove form, but their could be minute differences in form that have an big impact on how securely the male can hang on.

    I have observed mating pairs where at times the female became alarmed by my presence while the male did not - the female in such cases seem determined to get the male off of them before they flee, kicking and shaking to do so before taking flight.

    You probably did alarm the male, as I have seen them remain coupled for long after mating has occurred for mate guarding.

    I'll have to, once again, delay my own series of photos on this gorgeous beetle ;)

  3. Fascinating! Too often when I find an interesting insect or other critter I'll just pause long enough to get a decent photo of it and then move onto something else. It's easy to forget how rewarding it can be to just sit and observe something for a while.

  4. Hi, Lois. I'm going to try making some of your broccoli cheese bread. It probably won't look the same, but I'm hoping to capture the taste.

    Gee, Ted, I didn't mean to encroach on your turf. I'll lay off Tiger Beetles until I find my fourth species. Hope I can find something else interesting to talk about in the mean time.

  5. Sorry Steve - it was meant purely as a tongue-in-cheek comment.

  6. Whereas, I'm completely serious 100% of the time? My daughter taught me the meaning of the sideways smiley-winky face right after she informed me that lol did not mean "Lots of Luck". I'll be watching for your Cicindela rufiventris post.

  7. I love your images and the story that goes with them, Steve!

  8. This is a great post, Steve. My favorite description is "...with what resembled a flying tackle."

  9. Great series of shots, Steve! The side views of the "headlock" are particularly great! Superb write-up too!

  10. Thanks, Katie. Sorry you didn't have any luck with the grunion. I kept hoping I was going to read about the beach being covered with spawning fish.

    Thanks, TGIQ. Those beetles did like to pose. I'm glad you found a moment to check in. I've been keeping up with your northern adventures, but kind of miss hearing about what's been going on around home.