techniques

Goin’ fishin’

/ Ted C. MacRae / 7 Comments

For the past two days I’ve been in Sioux County, Nebraska – just east of Wyoming and just south of South Dakota. As I traveled up through the western panhandle to arrive at this spot, I was pleasantly surprised by the varied terrain – not at all the monotonously flat landscape that I expected. The landscape in this so-called Pine Ridge area is even more surprising – an impressive escarpment drops 1,400′ from the high shortgrass prairie down to an eery badlands below. The escarpment itself is forested with Ponderosa pine and is studded with numerous impressive buttes. The photos shown here were taken in Sowbelly Canyon – typical of the landscape along the escarpment – and in the badlands below Monroe Canyon a little further west.

Enough about pines and buttes – my business here is tiger beetles. I met up yesterday with tiger beetle aficionado Matt Brust, who recently took a position here at Chadron State College after finishing his Ph.D. in Lincoln. I’ve been corresponding with Matt for a bit now, and when I told him of my interest in doing a tiger beetle trip through western Nebraska, he was more than willing to show me around and hopefully help me find some of the more unusual species I was looking for. Of course, tops on the priority list was Cicindela nebraskana (prairie long-lipped tiger beetle). This beetle isn’t common anywhere within its range and just sneaks into the northwest corner of Nebraska, where the type locality is located. Until recently, the species was known from very few specimens in Nebraska. Matt did some intensive sampling a few years ago and located a few limited populations in the vicinity of the type locality. Yesterday, he took me to two of these localities, and we succeeded in finding one individual at the first and several at the second. It was at the type locality where I succeeded in getting this field photo. While admittedly harshly-sunlit, it is as far as I know the only field photograph of the species – all others that I’ve seen have been taken in terraria. I’ll fix it up a bit with Photoshop and re-post once I get back home. This species looks similar to the black morph of Cicindela purpurea audubonii, which co-occurs with C. nebraskana in Nebraska, but it lacks the bright white labrum and elytral markings of the former. Also, as I would learn during these past two days, it can be instantly recognized in the field by its shinier appearance and “stubbier” legs. A few days before my arrival, Matt succeeded in finding the species in the next county to the east, an eastern range extension of about 60 miles, and today I located the species at another new locality between the two. It is gratifying to have played a small role in increasing our knowledge about this unusual species.

My success with C. nebraskana has come despite uncooperative weather. A series of frontal systems has moved through the area since my arrival, resulting in several rain events and lots of cool, cloudy weather. Tiger beetles are sun-loving insects, and when it gets too cold or wet the adults dig in and don’t come out until the sun shines through or temps warm enough to trigger them to dig out. Matt had taken me to another locality – a sand embankment – where we might find the beautiful Cicindela lengi (blowout tiger beetle), but it rained prior to our arrival and we saw no activity. I tried finding adult burrows to dig them out, but the rain had obliterated any trace of the diggings, making their burrows impossible to find. We did, however, note an abundance of larval burrows. I went back to the spot today hoping to see some activity, but thick clouds and cool temps made that unlikely. This is when I decided to “go fishing.” Tiger beetle larval burrows are easily recognized by their perfect circular shape and clean “beveling” around the entrance (1st photo). Burrows of 3rd instars (the last larval instar in tiger beetles) are distinctly larger than those of 2nd instars (2nd photo), while those of 1st instars are smaller still (not shown). Larvae sit at the burrow entrance and ambush any suitable prey that comes too close. During cool, cloudy weather, however, they drop to the bottom of their burrow – up to a foot or more deep. A technique useful for extracting inactive larvae from their burrows is called fishing and involves inserting a thin grass stem down to the bottom of the burrow in an attempt to coax the larva into “taking the bait” and biting the end of the grass stem (3rd photo). The grass stem is then pulled up rapidly – much like setting the hook when fishing – in an attempt to pull the larva out of its burrow before it has a chance to let go of the stem. It can take a few tries, but with practice one can more often than not succeed at removing the grotesquely odd, yet beautiful larva (4th photo). Note the huge, heavily sclerotized head with upward facing jaws. The hump in the middle of the back is armed with forward-curved spines that helps the larva avoid being pulled out of the burrow by struggling prey (but they’re not so effective against obsessive cicindelophiles!). As I managed to “fish” larvae I placed them in a plastic container with their native soil. In the 5th photo, four larvae have already begun digging new burrows, and one more 3rd instar (L) along with a 2nd instar (R) has just been placed in the container. I’ll bring this container back with me and continue to feed the larvae live insects in the hopes of rearing them to adulthood. I cannot say with certainty that the larvae I collected represent C. lengi – other species that could potentially occur at this site include C. scutellaris (festive tiger beetle) and C. limbata (sandy tiger beetle). However, the locality is known for the abundant occurrence there of C. lengi, so I’m hopeful that that is what I’ve collected – we’ll know in a few weeks. In the meantime, I’ll have additional opportunities to look for this species, along with C. limbata, as I pass through the Sand Hills region later this week.

Tomorrow morning I head to the Black Hills in South Dakota, where I hope to find not only Cicindela longilabris laurentii (Boreal long-lipped tiger beetle) in the high pine forests, but also intergrades between this species and the closely related C. nebraskana in the more open habitats of the middle latitudes. Look for an update in a couple days or so.

Digging tiger beetles

/ Ted C. MacRae / 7 Comments

After driving almost 600 miles on Friday, I was ready for some tiger beetle action. A quick 2-hour drive this morning got me to the first set of localities in extreme southwestern Nebraska and just across the border into Colorado (“B” thru “D” in the previously posted map). Compared to the other localities I have lined up for the trip, these were the most vague – based on published records from more than a century ago with no recent ‘ground intelligence.’ I wasn’t too concerned about having success at these spots, I just wanted a potentially interesting area to explore after a day of driving before completing my voyage to the first real target areas up in the northwestern corner of Nebraska. I could’ve taken a more direct line along I-80 and explored areas along that route, but I’ll be exploring that route on my return trip.

My first stop at Benkelman was a bust – I was looking for some sand blows in the hopes of finding Cicindela limbata, but a half hour of so of driving around the area turned up nothing. I stopped at some exposed clay to see if I might encounter C. denverensis but only saw a couple of the ubiquitous C. punctulata. Haigler – a half hour to the west – was more productive. I found a spot with access down along the Republican River (at only 2 yards in width, it is beyond me how this qualifies as a “river”) and found several typical sand associated species – C. scutellaris (pictured) and C. formosa, both nominotypical forms which look very different from the populations we have in Missouri, and several C. tranquebarica individuals that show the bold markings characteristic of the northern Great Plains subspecies kirbyi (the first time I’ve seen this subspecies). My 104 year-old literature reference suggested C. fulgida occurred around salt marshes in the area, but no such habitats were found – probably degraded long ago, or even worse obliterated in the interest of “improving” the land for agriculture. Another half hour drive got me to Wray, just across the border in Colorado, where C. limbata again had been recorded from sand hills above the Republican Trickle. These sand hills were easily located, but the completely barren blows that the species requires, again, were not found – probably allowed/encouraged to grow over. As it was now the heat of the day (a very pleasant low 80’s), the common sand species C. formosa and C. scutellaris were now digging in to avoid the heat.

Although it is well known that adult tiger beetles dig burrows to spend the night, I haven’t really seen much in the literature that talks about their daytime burrowing habits, how to recognize the burrows, and how to dig them out (okay, so now my double entendre of a title makes sense, cuz you see I really ‘dig’ tiger beetles… and I’m digging them from their burrows… oh well, it seemed funny when I thought of it). Many other insects also burrow in the sand, and some of them – especially those of the many ‘digger’ wasps and ground nesting bees – can look very similar to (and sometimes outnumber) those of tiger beetles. In my experience, adult tiger tiger beetle burrows have a more ‘flattened’ aspect to them (1st photo), while those of wasps and bees are more rounded. Fresh burrows from both groups will have moist diggings thrown to one side (in old burrows – often uninhabited – the diggings will be dry), but those of tiger beetles appear more ‘fanned’ while those of hymenopterans are more ‘piled.’ I use a knife to excavate the sand away from the entrance in thin vertical slices (2nd photo), slightly undercutting the burrow to prevent sand from falling into it (and making it impossible to follow). Wasp and bee burrows look more round during excavation and often make a hard turn downward, while those of tiger beetles continue looking very flattened and usually stay rather shallow. If somebody is home, they will be encountered without too much digging – these photos show a C. scutellaris adult peaking out head first and a C. formosa who was still in the act of excavating (done by kicking the sand backwards while backing towards the entrance). I stumbled onto this technique last year during my first encounter with C. limbata – had I not done so I probably would’ve walked away with only a single specimen.

Tomorrow, I hope to have encountered C. nebraskana and C. lengi. Cicindela decemnotata is a long shot, but hope springs eternal…

The hunt for Cicindela celeripes

/ Ted C. MacRae / 12 Comments

One of the more enigmatic tiger beetle species in North America is Cicindela celeripes LeConte (swift tiger beetle). This small (6-8 mm), flightless species has been recorded from a restricted area of the eastern and southern Great Plains – from eastern Nebraska and westernmost Iowa south through Kansas to western Oklahoma and the Texas panhandle (Hoback and Riggins 2001, Pearson et al. 2006). Unfortunately, populations of this species appear to have suffered severe declines. It apparently is holding strong in the Flint Hills region of Kansas, but many of the records from outside of that area date back more than a century. Reportedly once common on the bluff prairies along the Missouri River, it has not been seen in Nebraska since 1915 and may have been extirpated from that state (Brust et al. 2005). The reasons for this decline undoubtedly involve loss of preferred habitat – upland prairies and grasslands with clay or loess soils and sparse or patchy vegetation. Areas supporting these native habitats have been drastically reduced since European settlement of the region, and suppression of fire – so vital to prairie ecosystems – has led to extensive woody encroachment on the few prairie relicts that do remain. Unlike many other tiger beetle species that have been able to adapt to these anthropogenic changes, this species apparently cannot survive in such altered habitats.

Chris Brown and I have been interested in this species ever since we began surveying the tiger beetles of Missouri. It has not yet been recorded from the state, but we have long suspected that it might occur in extreme northwest Missouri. It is here where the Loess Hill prairies along the Missouri River reach their southern terminus. (Incidentally, the Loess Hills are themselves a globally significant geological landform, possessing natural features rarely found elsewhere on earth. They will be the subject of a future post). We have searched several of what we consider to be the most promising potential sites for this species in Missouri, though without success. Nevertheless, we remain optimistic that the species might eventually be found in Missouri and has simply been overlooked due to the limited temporal occurrence, small size, rapid running capabilities, and tendency of adults to dart rapidly to the bases of grass clumps where they hide (Pearson et al. 2006). Furthermore, even though the species has not been seen recently in adjacent areas of Nebraska where it has been recorded in the past, it has been seen recently in a few Loess Hill prairie remnants just to the north in Iowa.

A few weeks ago, I was fortunate to receive specific locality information for one of the recently located Iowa populations. Armed with site descriptions, Google maps, photographs, and whatever book learnin’ I had gained about this species, my colleague and I made the long drive to southwestern Iowa in hopes of locating the population for ourselves, seeing adults in their native habitat, and using the learnings we would gain about their habitat preferences and field behavior to augment our efforts to eventually locate the species in northwestern Missouri. At mid-July, we were nearing the end of the adult activity period, but adults had been observed at the site the weekend prior, so we felt reasonably confident that adults might still be found. Additionally, fresh off of our recent success at locating the related Cicindela cursitans in Missouri (another small, flightless, fast-running species), we were hopeful that we now possessed the proper “search image” to recognize C. celeripes in the field should we have the good fortune to encounter it.

Walking into the area, I was impressed at the extensiveness of the prairie habitat – much larger than any of Missouri’s Loess Hill prairies. The presence of large, charred red-cedar cadavers on the lower slopes revealed active management for prairie restoration. We later learned from the area manager that the restoration area had been acquired from a neighboring landowner who had used the land for grazing and sold it when it became unproductive. I can only imagine the second thoughts that landowner must have had when subsequent burn regimes and woody growth removal prompted a return to the beautifully lush sea of prairie vegetation that now covered the hills. As we approached the area where we decided the beetles must have been seen, we started searching slowly and deliberately – looking carefully for any movement between the clumps of grass. It didn’t appear to be prime habitat for C. celeripes – the vegetation was just so thick, with only small openings among the plants. We continued to scour the area closely but saw nothing, and my optimism began to wane. Wrong spot? – I don’t think so. Bad search image? – hard to imagine, considering its similarity to C. cursitans. Too late? – could be.

After it became obvious we were searching the same gaps in the vegetation repeatedly, I started walking towards a small cut further down the hillside that I had noticed earlier (just visible in the previous photo). I had thought, “That’s tiger beetle land down there!” My optimism increased when I reached the cut, seeing the remains of an old, overgrown 2-track leading through the cut and on down the hillside. Vegetation was much sparser within and below the cut – it looked perfect. Chris had become distracted taking photographs of something, so I began searching. I’d been in the cut a few minutes when I thought I saw something flash across a bare patch out of the corner of my eye – was that it? It had to be. I carefully inspected around the base of every clump of vegetation at my feet but found nothing. It must have been wishful thinking – just another spider. I continued on down the cut, and within a few more minutes I saw the flash again – this time there was no doubt as to what it was, and I had a lock on it. I started slapping the ground frantically as the little guy darted erratically under, around, and over my hands. In the few seconds while this was happening, I was simultaneously exuberant at having succeeded in finding it, utterly astounded by its speed and evasiveness, and desperately afraid that it was getting away – swift tiger beetle, indeed! Persistence paid off, however, and eventually I had it firmly in my grasp.

We would see a total of seven individuals that day. Most of them were within or immediately below the cut, while another individual was seen much further down the 2-track. Mindful of the population declines this species has experienced, we decided to capture just three individuals (even though by this point in the season mating and oviposition would have been largely complete) in hopes that at least one would survive the trip back to the lab for photographs. Our primary goal – to see the species in its native habitat – had been accomplished. We now turned our attention to attempting in situ field photographs. This would prove to be too difficult a task – each beetle we located immediately ran for cover, and flushing it out only caused it to dart to another clump of vegetation. This scenario repeated with each beetle until eventually it simply vanished. We would have to settle for photographs of our captured specimens in a confined arena – a few of which are shown here. The beetles were photographed on a chunk of native loess taken from the site, and no chilling or other “calming” techniques were used. Spomer et al. (2008, Field Guide to the Tiger Beetles of Nebraska and South Dakota) state that C. celeripes is a delicate species that does not do well in captivity. It has never been reared, and the larva is unknown. Nevertheless, I placed the chunk of native loess in a plastic tupperware container and transplanted into one corner a small clump of bluegrass from my yard. The soil around the grass clump is kept moist, and every few days I have placed various small insects in the container. Of the three individuals that we brought back, two died within two days. The third individual (these photographs), however, has now survived for four weeks! Moreover, it is a female, and during the past two weeks six larval burrows have appeared in the soil (and another egg was seen on the soil surface just yesterday). Indeed, an egg can be seen in the upper right of the first photo. It remains to be seen whether I will be successful at rearing them to adulthood; however, I’m hopeful this can be accomplished using methods described for C. cursitans (Brust et al. 2005).

Do I still think C. celeripes occurs in Missouri? I don’t know – on one hand, the mixed grass Loess Hill prairie habitats in which the beetle lives in Iowa do extend south into Missouri, and the beetle could be inhabiting them but be easily overlooked for the reasons I’ve already mentioned. However, Missouri’s Loess Hill prairie relicts are small, both in number and in size, and highly disjunct. Such features increase the likelihood of localized extinctions and hamper recolonization through dispersal, especially in flightless species that must traverse unsuitable habitat. With its adult activity period winding down, renewed efforts to locate this species in Missouri will have to wait until next season. Hopefully, the knowledge we gained this season will help this become a reality. For now, the hunt continues…

(closing photo by C. Brown)