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.
I’ve been busy searching for Tiger Beetles this summer. I’ve found adult specimens of three species and have been anxious to find my first larva. The larvae are found in burrows that they create in the soil. The trick is to find an active burrow and then wait for the larva to come to the entrance where it will wait to ambush small insect prey. My most recent search revealed many pinhole sized burrows in the clay soil.
There are many things that make small holes in the ground. I’ve been fooled by bees into thinking that their burrows were those of tiger beetle larvae, but I’ve never seen a bee small enough to fit into a pin hole. It’s been a couple of weeks since I’ve seen any adult tiger beetles in this location, so I’ve been expecting that their eggs would hatch and the resulting tiny larvae would dig tiny burrows. These holes looked like just what I had imagined finding.
I settled down to wait for something to show itself in the hole. After a few minutes, I noticed that there was now a reflection where before the hole had been dark. There was something in the hole.
I managed to take several photos, but my camera doesn’t do very well with pinhole sized subjects. Fortunately, I have a book that shows an unfocused picture of a tiger beetle larva at the entrance to its burrow and my photo is a very close match. As the subjects grow I should be able to get some better shots.
I found the pin hole burrows in this area that was earlier filled with adult Cicindela rufiventris. I’m assuming that the larvae represent that species.
