Sorry about the noisy video – it was shot in one of our walk-in growth chambers with fans going full-bore! Anyway, the video shows a couple of mating pairs of Cylindera celeripes (swift tiger beetle) that I brought back from the Loess Hills of extreme northwest Missouri this past weekend. Watch carefully and you’ll see the first pair actively copulating before they break apart. After that I pan over to the second pair, which is not actively mating but have remained coupled as an example of behavior called “mate guarding” You might also notice a few very small green “bugs” in the container – these are 2nd-instar Lygus nymphs, which I placed in the container earlier in the day as prey – it was quite a sight to see the tiger beetles immediately begin chowing down on them! At the end of the video, I poke at the second mating pair with my forefinger to give an indication of their tiny size – this flightless species is one of the smallest in all of North America! Knowing how tiny the beetles are and how well they blend into their surroundings (you’ll have to imagine the 1-2 ft of plant growth that was surrounding them in the field), you can appreciate just how difficult these beetles are to detect in their native habitat.
There is a “good news, bad news” aspect to the story behind these beetles. This rare Great Plains species was unknown from Missouri until last year, when we (Chris Brown and I) discovered it in loess hilltop prairie remnants at Brickyard Hill, Star School Hill Prairie, and McCormack Loess Mounds Conservation Areas. Loess hilltop prairie is among Missouri’s most critically endangered natural community due to its restricted occurrence at the southern tip of the Loess Hills landform and more than a century of overgrazing and relentless encroachment by woody vegetation and invasive exotics. The sites where we found the beetle last year contain the highest quality loess hilltop prairie remnants in Missouri, so we are now taking a more thorough look at some of the smaller remnants that still exist in the area. The most promising of these are at Squaw Creek National Wildlife Refuge and on several privately owned lands near the known sites, and these were the sites that I searched this past weekend. Some of these sites looked promising (one in particular looked excellent), but thorough searching at each revealed no beetles. By the time I finished searching the last of them I had begun to wonder if: 1) my “search image” for the species had gotten rusty, or 2) my timing was a bit too early (last year’s populations were discovered in late June). To test this, we (daughter Madison and I) returned to one of the known sites (McCormack) where we had seen only two beetles last year (unable to capture either one). As we hiked along the ridge top leading to the spot where we saw them, I kept a close watch on the narrow trail in front of me. Nothing. However, as soon as I came upon “the spot” I saw one! I dropped to my knees and slapped my hands down on the ground, forming an “arena” between my two thumbs and forefingers, but the beetle ran over my hand too quickly and escaped. No matter – in less than a minute I saw another one and successfully trapped it under my fingers as it ran over my other hand. During the next 15-20 minutes I would see at least eight individuals along the narrow trail in this single spot. While it was gratifying to see more individuals at this site than we had seen last year, it also meant that the timing of my searches at the other sites was fine and that I was not suffering from a rusty search image. The beetle could still be at those sites where I had failed to find it, but if it is then it certainly does not occur in very high numbers. It also bothers me that at this site the beetle seems to be restricted to one isolated ridge, which appears not to have been burned in recent years (in contrast to the rest of the preserve, which seems to have been burned within the past year or so). I searched all the remaining ridge top again thoroughly after finding the beetles again this year, but no beetles were seen anywhere except this tiny spot where we have now seen beetles in successive years.
Missouri’s few existing loess hilltop prairie remnants are not only small but highly disjunct, and the flightless nature of the beetle makes re-colonization of a remnant unlikely in the event of a localized extirpation. There is obviously much we still do not know about the impact of burning on the beetle and how best to devise management plans that consider both the habitat and the beetle. However, one thing is clear – both the habitat and the beetle are critically imperiled in Missouri, and the fate of both are in our hands, right here and right now! We’d better get this figured out quick if we’re going to save both, and there seems to be little room for error. For my part, in addition to pinpointing where our populations occur and precisely what habitats are supporting them, I am trying to develop an effective rearing technique for this never-before-reared species in the event that captive rearing becomes necessary for reintroduction or augmentation of native populations. The adults seem very delicate and do not travel well, but I have found that if I prepare a terrarium in the field for transporting the adults then they survive well – even when traveling for several days. The container measures 6 1/4” H x 8” L, and I’ve placed a chunk of native soil cut from the site where I found the beetles and kept intact. The debris on the soil surface is intact as well, but the plants growing in the soil have (obviously) been trimmed. I’ll collect eggs from these individuals and experiment with different methods that I’ve been working on for rearing the larvae to see which are the most efficient and effective.
Copyright © Ted C. MacRae 2010