Beetles with a Checkered Past (and Future)

It's been a good summer so far for these beauties:

Trichodes nuttali, Illinois Beach SP, Lake Co, IL, 6/29/2014

Enoclerus analis, Lyons Woods FP, Lake Co, IL 7/30/2013

Thanasimus dubius, Lyons Woods FP, Lake Co, IL 6/2/2014

These are all Checkered Beetles, in the family Cleridae. The family is a small one, only 3600 species worldwide, with only 300 or so in North America. (That's about 1% of the 350,000 species of beetle worldwide*, and about 0.1% of the 25,000 beetles recorded from North America.)

They're predators, eating other insects. The larvae often feed on wood-boring larvae, including those of Pine Bark Beetles responsible for quite a few large-scale losses of trees in the western and south-eastern US. Which explains why this little tiny family still warrants over 5,000 citations on Google Scholar.

Interestingly, they use the sex pheromones of their prey to find them. The technical term for this is a kairomone, which is a chemical produced by one species that ends up benefiting another species. Herms, et al. looked at this in the predator-prey pair Ips pini (a bark beetle) and Thanasimus dubius (the last Clerid shown above). (1)  Billings & Cameron showed that different predatory beetles respond to different genera of pine bark beetles, an interesting bit of specialization. (2) (They also showed that pine sawyer beetles, Monochamus titillator, responded to one of the bark beetles. Given their habit of laying eggs in freshly dead pine trees, this makes sense. They only responded to one species of beetle, though, which leads me to wonder if that beetle is more lethal to the pines, or if both the bark beetle and the sawyer beetle show preferences for certain species of pine.)

Beetles can be surprisingly attractive little critters, but it shouldn't surprise me by now just how intriguing their lives can be.

*All of these figures from Bugguide.net.

(1) Herms, D. A., Haack, R. A., & Ayres, B. D. (1991). Variation in semiochemical-mediated prey-predator interaction: Ips pini (Scolytidae) andThanasimus dubius (Cleridae). Journal of chemical ecology, 17(8), 1705-1714.

 

(2) Billings, R. F., & Cameron, R.S. (1984). Kairomonal responses of Coleoptera, Monochamus titillator (Cerambycidae), Thanasimus dubius (Cleridae), and Temnochila virescens (Trogositidae), to behavioral chemicals of southern pine bark beetles (Coleoptera: Scolytidae). Environmental Entomology, 13(6), 1542-1548.

 

Return of the Prairie?

Here's a nice find from this morning, first located by a friend of mine:

Prairie Warbler (Setophaga discolor), Grant Woods FP, Lake Co, IL  6/27/2014

This is a male Prairie Warbler (Setophaga discolor), and he's only the third one I've ever run across in the county. The first one, in fact, I never did manage to see. Thankfully, they have a very distinctive voice -- a slightly buzzy, very musical series of notes running up the scale. Their song always reminds me of Arethra Franklin trying to sing a Northern Parula ditty.

They breed in early-successional shrublands, which are in rather short supply in this area these days. Back in the 70's, though, they bred in Illinois Beach State Park. That habitat hasn't changed much over the years, and I don't know why they disappeared.

I mentioned that this was the third one I've found here? The first two were last year in May. Given that this guy's been singing away for at least two weeks, and he was joined by a second male, I have to wonder if this is a signal of a range expansion back into the county. In the case of this particular male, it's likely to be an unsuccessful one, since he's still singing his heart out at the end of June. (Typically, a male that's found a mate will spend a lot less time singing by now, since there's no longer any need to attract a female.) But that's the way that ranges grow -- the first few birds into a new area will probably not succeed. Once a couple of birds have found mates, and we have a few nestlings who have grown up here, then the next birds to wander into the area will see a reason to stay, and we have a new expected species.

Evolution can be seen as an exploration of the incredibly large universe of possible genetic programs, set against a wildly varying environment of constraints. An occasional individual wanders into new territory, and if it's really lucky, an entire population will someday follow it. But that's an abstract way to view things. Genetic programs only evolve when they're in a body that can actually do things, and in this case, we're seeing the abstract concept of exploration playing out in very concrete, and very musical, little warblers.

Wolves and Bears, Oh My!

Rain threatened all morning, then class in the evening, so here's a couple of zoo shots:

Red Wolf (Canis rufus), Henry Doorley Zoo, Springfield, IL 5/21/2013

This is a Red Wolf (Canis rufus).

Mexican Gray Wolf (C. lupus baileyi), Cheyenne Mountain Zoo, Colorado Springs, CO 12/27/2013

This is a Mexican Gray Wolf (C. lupus baileyi).

At various times, the Red Wolf has been considered a subspecies of the Gray Wolf (thus C. lupus rufus) (1) and a hybrid of Coyotes (C. latrans) and Eastern Gray Wolves (C. lupus lycaon) (2, 3). (It's been argued that Eastern Gray Wolves aren't properly placed in C. lupus, (4) as well.) This is all a rather obscure academic dispute, I suppose. Even most people who care that there are wolves in the US don't know the ins and outs of their relationships. Except for one thing -- Red Wolves are a critically endangered species, with a re-introduced population living on Alligator River NWR in northeastern North Carolina. If they were indeed to be considered a subspecies of the Gray Wolf, the reintroduction program might itself be endangered. Trying to do science well is hard enough. Trying to do it well with this sort of controversy lurking behind every abstract must be a bit of a nightmare.

Here's another couple of critters with similar histories:

Alaskan Brown Bear (Ursus arctos alascensis), Alaska Zoo, Anchorage, AK 8/12/2012

Grizzly Bear (U. arctos horribilis), Cheyenne Mountain Zoo, 12/27/2013

These are both Brown Bears (Ursus arctos), although currently considered different subspecies. There have been quite a few different subspecies described, from as few as 5 to as many as 90! In the 1920's and 1930's, though, the Grizzly (Ursus horribilis) was still considered a separate species. (5) Again, since Grizzlies are listed as endangered, while Brown Bears as a whole aren't, these decisions actually matter. And here's an interesting question for the near future, along these lines:

Polar Bear (U. maritimus), Cincinnati Zoo, Cincinnati, OH 3/29/2012

This, of course, is a Polar Bear (Ursus maritimus). If you're into bears, you've probably heard of the Grolar Bears that have recently been shot in the Arctic reaches of North America. Those would be Ursus maritimus X arctos hybrids. Hybrids between species indicate that those species are closely related, and indeed research suggests divergence times as old as 5 million years (6) and as recent as
150,000 years. (7) While there is evidence from DNA of hybridization, and a couple of older specimens, recent discoveries of wild grolar bears has raised the specter of climate change pushing the two species into more contact, with grizzlies moving north as the climate warms and polar bears spending more time on land as the ice melts. If they are capable of hybridizing, and the hybrids are born into a changing world that favors a melding of the two species, could we see the recently evolved Polar Bear merging back into the Brown Bear they evolved from? And if so, what would we call the resulting population, and how would we deal with it in terms of conservation?

Science is all about trying to refine our view of the world. Often that requires a focus which nearly shuts out all but the little piece we're working on. But the rules our world plays by don't always allow the Ivory Tower approach -- the things we do really do make differences in the world around us.


(1) Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press.
  
(2) VonHolt, BM; et al (12 May 2011). "A genome-wide perspective on the evolutionary history of enigmatic wolf-like canids". Genome Res 21 (8): 1294–305. 

(3) Wayne, R. and S.Jenks. 1991. Mitochondrial DNA analysis supports extensive hybridization of the endangered red wolf (Canis rufus)" Nature 351:565-68.
 
(4) Chambers SM, Fain SR, Fazio B, Amaral M (2012). "An account of the taxonomy of North American wolves from morphological and genetic analyses". North American Fauna 77: 1–67. 

(5) Baggley, G. F. (1936). Status and distribution of the grizzly bear (Ursus horribilis) in the United States. In Transactions of the North American Wildlife Conference (Vol. 1, pp. 646-652).

 

(6) Miller W, Schuster SC, Welch AJ, et al. (July 2012). "Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change". Proc Natl Acad Sci U S A 109 (36): E2382–90.

 

(7) Lindqvist, Charlotte; Schuster, Stephan C.; Sun, Yazhou; Talbot, Sandra L.; Qi, Ji; Ratan, Aakrosh; Tomsho, Lynn P.; Kasson, Lindsay et al. (2010). "Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear". Proceedings of the National Academy of Sciences 107 (11): 5053–5057.

Seeing the World through Other Eyes

I came across this little beauty this afternoon at Van Patten Woods:

Rainbow Bluet (Enallagma antennatum), Van Patten Woods FP, Lake Co, IL 6/21/2014

This is a female Rainbow Bluet, one of our prettiest damselflies. One of the neat thing about damselflies (and dragonflies) is their ability to navigate by polarized light. (1) Since polarization varies across the sky depending upon the sun's position, this is a very useful trick. Water reflects light in a polarized fashion as well, which is probably useful for a dragonfly as well. Other insects can do this as well:

Bibio albipennis, Lyons Woods FP, Lake Co, IL 6/2/2014

Golden Northern Bumblebee (Bombus fervidus), Gander Mt. FP, Lake Co, IL 8/3/2013

Many of them can also see ultraviolet light, which bees use to locate the appropriate flowers and the nectar within those flowers. (2) These guys have evolved strategies to take advantage of this ability:

Six-spotted Orbweaver (Araniella displicata), Ryerson FP, Lake Co, IL 5/31/2014

Orbweaver spiders place UV-reflective decorations within their webs to actually attract prey -- bait, if you will. (3)

When you're wondering what your favorite pet thinks about the world, it's worth remembering that he or she almost certainly doesn't perceive the world the way you do. So much of ecology would be completely hidden without the tools we have, based on theory hashed out by generations of physicists, built by engineers for those biologists with the imagination to conceive of a world that looks completely different than the one we see.

(1) Meyer, E. P., & Labhart, T. (1993). Morphological specializations of dorsal rim ommatidia in the compound eye of dragonflies and damselfies (Odonata). Cell and tissue research, 272(1), 17-22.

 

(2) Guldberg, L. D., & Atsatt, P. R. (1975). Frequency of reflection and absorption of ultraviolet light in flowering plants. American Midland Naturalist, 35-43.

 

(3) Craig, C. L., & Bernard, G. D. (1990). Insect attraction to ultraviolet-reflecting spider webs and web decorations. Ecology, 616-623.

 

 

Family Trees Revisited

Here's an interesting trio:

Edith's Checkerspot (Euphydryas editha), Flaming Gorge NRA, Daggett Co, UT 5/27/13

Steel-blue Cricket Hunter, (Chlorion aerarium), Illinois Beach SP, Lake Co, IL 8/2/2013

Red-bellied Snake (Storeria occipitomaculata), Lyons Woods FP, Lake Co, IL 3/5/2012

What's the link here? These are all illustrations of a common pattern in evolution. Not so many years ago, butterfly guides talked about 3 suborders of Lepidoptera -- moths, butterflies, and skippers. Similarly, Hymenopterans were split into three groups -- parasitic wasps, stinging wasps and bees, and sawflies. The squamate reptiles consisted of two -- the snakes, and the lizards. In each case, the assumption was that these groups had split apart early, and then each had diversified on its own.

Here's a rough cladogram, to give an idea:

Cladistic analysis, these days greatly enhanced by DNA analysis, has shown that this pattern doesn't often hold. Instead, what we see is early splits leading to "basal" groups that don't diversify much, (like several of the sawfly families and some "primitive" moths), a succession of further splits that don't do much, then one or two groups that split and apparently cross some sort of adaptive threshold, followed by an impressive radiation. So we find that the sawflies, for example, are actually not a natural group at all -- they're just those hymenopterans that didn't become wasps. Here's a more recent conception:

We find the same with Lepidopterans -- butterflies make up part of one suborder, along with most of our moths. Even within that suborder, most of the groups are moths, as are a large majority of the species. The old breakdown of moth, butterfly, skipper isn't tenable.

Even the snakes, clearly a natural group themselves, turn out to be nested within one of several suborders of lizards, long thought to be a separate group.

(A quick note on the use of scare quotes above -- these are two terms I cordially detest when used this way. A primitive species is one that died out a long time ago -- modern species have all been evolving since that early ur-ancestor. And a basal group, if you examine any cladogram that purports to show "the basal" species, is whichever lineage that emerged from that first split either without diversifying much, without becoming "interesting", or that has since lost most of its earlier diversity.)

Bombyliids Away!

Here's a find from Gander Mountain today:

Villa arenicola, Gander Mt. FP, Lake Co, IL 5/28/2014

This is a bee fly, in the family Bombyliidae. I'm pretty sure it's in the genus Villa, perhaps V. arenicola, but apparently the genus is in serious need of revision. (1)

This is a diverse group, both in terms of species (>5,000 worldwide) and structure. This is a small sample of the diversity -- many of the subfamilies I've never seen:

Exprosopa decora, Illinois Beach State Park, Lake Co, IL 7/21/2013

Poecilanthrax alcyon, Illinois Beach State Park, 9/3/2012

Systoechus vulgaris, Illinois Beach State Park, 7/12/2013

Despite the name Bee Fly, these are harmless nectar-feeders. That fearsome proboscis on Systoechus isn't for drawing blood! However, if you're a beetle grub or a wasp larva, these are scary critters. While the adults are nectar feeders, their larvae are parasitoids, waiting for their hosts to pupate before eating them alive. This sort of parasitism has been well-studied, especially in Hymenopterans, and Bee Flies present a perfect second opportunity for testing hypotheses.  Yeates & Greathead did exactly that, finding that most clades had rather broad host preferences. (2) They argue that this is part of the explanation for the relatively low number of species in the family. (By comparison, Ichneumonidae (parasitic wasps) boasts >5,000 species just in North America and 60,000 to 100,000 worldwide!) (3)


(1) http://bugguide.net/node/view/9865

(2) Yeates, D. K., & Greathead, D. (1997). The evolutionary pattern of host use in the Bombyliidae (Diptera): a diverse family of parasitoid flies. Biological Journal of the Linnean Society, 60(2), 149-185.

(3) http://bugguide.net/node/view/150

Musing on Naming

Busy prepping for the start of the summer semester today, so here's a few shots from other places:

American Robin, (Turdus migratorius), Waukegan Beach,
Lake Co, IL 5/7/2014

This is an American Robin (Turdus migratorius).

Northern Parula (Setophaga americana),
Tawas Point SP, Iosco Co, MI 5/24/2014

This one's a Northern Parula (Setophaga americana), one of the Wood-Warblers (Parulidae).

Yellow-bellied Flycatcher (Empidonax flaviventris),
Waukegan Beach, Lake Co, IL 5/20/2012 

And this one's a Yellow-bellied Flycatcher (Empidonax flaviventris), one of the Tyrant Flycatchers (Tyrannidae).

What do these three have in common? They are all part of an explanation for why I insist on including scientific names, even when, as here, they have standardized common names as well.

I don't have a picture of a European Robin (Erithacus rubecula), never having traveled to Europe, but it isn't in the same family as ours. Ours is a Thrush (family Turdidae), whereas the European version is in the family Muscicapidae, or Old-World Flycatchers. Here's another example of an Old-World Flycatcher:

Oriental Magpie-Robin (Copsychus saularis), National Aviary,
Pittsburgh, PA 3/28/2012

This is an Oriental Magpie-Robin (Copsychus saularis), from the National Aviary in Pittsburgh, PA. (Well worth the visit!) They're named Old-World Flycatchers to distinguish them from our Tyrant Flycatchers (family Tyrannidae), which aren't closely related at all!

Similarly, our Wood-Warblers got their name because of a perceived resemblance to Old-World Warblers (formerly Sylviidae, now split into several families). Here's an example, in the new family Phylloscopidae:


Arctic Warbler, (Phylloscopus borealis), Salmon Lake, Nome, AK 8/10/2012

This is an Arctic Warbler (Phylloscopus borealis), from Salmon Lake, north of Nome, AK.

Where did this hodge-podge of names come from? There are several sources of confusion. First, when the first Europeans began settling the New World, they naturally named the critters they saw after familiar species. (Sci-fi authors do this a lot, even today.) Once we started to learn how different things were here, the common names were in such everyday use that changing them would be impossible. Second, our ideas of avian taxonomy have changed a lot since the 18th and 19th century when most of the names were being worked out. So much so, in fact, that it would be amazing if common names still fit. Here's a couple of examples of that process:


Evening Grosbeak (Coccothraustes vespertinus),
Lake Co, IL 11/2/2012

Rose-breasted Grosbeak, (Pheucticus ludovicianus),
Hardwick Pines SP, Crawford Co, MI 5/22/2012

These are both Grosbeaks, but the Evening Grosbeak (Coccothraustes vespertinus) is in the family Fringillidae and the Rose-breasted Grosbeak (Pheucticus ludovicianus) is in the family Cardinalidae. And speaking of the family Cardinalidae:



Northern Cardinal (Cardinalis cardinalis)
Louisville Zoo, KY, 3/28/2012

Red-capped Cardinal (Paroaria capitata)
Lincoln Park Zoo, IL 11/30/2013

The one on the left is a Northern Cardinal (Cardinalis cardinalis). The one on the right is a Red-capped Cardinal (Paroaria capitata), which was thought to be in Cardinalidae when named, but is now considered to be a tanager, in the family Thraupidae. That's okay, though, because our North American tanagers are now considered to be in the family Cardinalidae!

Summer Tanager (Piranga ludoviciana),
Konza Prairie, Riley Co, KS 5/23/2013

The nice thing about using the scientific names is that it's very easy to simply reassign the groups to other groups, without having to change the finer details. So we could move the Piranga tanagers to the Cardinalidae without having to actually change their names. The price we pay, of course, is a set of common names that bears less resemblance to modern taxonomic ideas with every passing paper.

And that's why scientific names will continue to be used!

Back to What?

My first visit to Reed-Turner Woodlands Nature Preserve turned up this beauty:

Condylostylus patibulatus, Reed-Turner Woodlands Nature Preserve,
Lake Co, IL 6/8/2014

This is Condylostylus patibulatus, as far as I can tell. It's a member of the family Dolichopodidae, or Long-legged Flies. Despite it's tiny size and gleaming appearance, it's a voracious predator of truly tiny insects!

Today, though, it's an excuse to discuss something else: this sign, or rather the thinking behind it.

Reed-Turner Woodland Nature Preserve,
Long Grove, Lake Co, IL 6/8/2014

Seeing this brought a natural question to mind -- what is a "low-quality tree"? In this case, I suspect that European Buckthorn was a major player. But the very idea of high- vs. low-quality plants and animals says something important about us as conservationists (and indeed, as people). When we are managing a piece of land, we have an idea in mind of what that landscape is supposed to look like, and how it's supposed to function. Where do we get those ideas?

In a recent post, I discussed the use of fire to maintain our local prairies and oak woods. What I never discussed there was why we would want to maintain those environments. Why not allow our prairies to grow into forests, and our oaks to be replaced by maples?

A seemingly common viewpoint in this regards is that we want a "natural" landscape. So, to maintain this landscape:


Spring Bluff FP, Lake Co, IL 5/25/2012

We practice this:


Prescribed Burn, Illinois Beach SP, Lake Co, IL 11/17/2011

I actually discussed this with a local biologist once, and he remarked that he was attempting to mimic a "non-anthropogenic" landscape. (We were actually discussing the timing of controlled burns, not the advisability of them.) But that reminded me of a minor epiphany I had several years ago -- in Lake County, outside of perhaps a few bogs, there is no such thing! The last glacial maximum ended 10-12,000  years ago. Yet we know that paleo-indians were in North America at least 14,000 years ago, and probably even more. Carbon-dating of remains from a mammoth kill site in Kenosha Co, just north of here, suggest human presence back to 14,500 years ago right in this area. (1) I don't know the history after the glaciers receded, but it seems unlikely that humans took more than a few thousand years to move in here. So our landscape has had humans living on it for thousands of years! And one thing we know about the Indians just pre-Colombus is that they used fire to sculpt the landscape at a scale we have rarely felt brave enough to attempt.

So back to my question: why maintain these environments?

With all of the intercontinental travel we indulge in these days (as a species, anyways!), many of the "low-quality" species we're discussing are introduced from elsewhere. What that means in this context is that if we simply sit back and allow our landscapes to change as they will, eventually they'll look the same as everywhere else on Earth (climate permitting, anyways). So one answer to my question is that we work so hard in order to maintain the unique quality of our landscapes -- once they're gone, they could be gone forever.

Another answer is that in an ever-changing world, most of the natural landscapes we are likely to encounter are fairly stable, and that means that they work well in terms of nutrient cycling, water cycling, etc. Those processes are called ecosystem services when they benefit us, and preserving ecosystem services should be a primary concern of anyone who manages a large-scale landscape. Since stable landscapes already preserve those services, they are good things both to keep and to study. If we allow those landscapes to change too fast, we lose that model and we may lose the services directly as well.

One last answer is that we work to maintain those environments because of our attachment to history. We like to know how things used to be, whether it's human society or the environment we carved those societies out of. Reading about the arrival of the Mayflower is interesting stuff, if presented correctly. Imagine how much more interesting it might be if you could go there and see what Plymouth Town looked like as they came ashore!

That ideal is lost for Plymouth, or Baltimore or Roanoke. But if you want to better understand the pioneers' journeys to Oregon, you can go out to Wyoming and stand in the very wheel ruts laid down by the covered wagons, and look out over a landscape that has only changed in the details. Around here, you can't see a broad prairie running between distant oak openings, but there a few little patches where you can see what an oak opening would have been like, and ponder the wonder of a pioneer kid finding his first deer wandering through one.

(1) http://www.kenosha.org/wp-museum/exhibits-2/mammoths-kenosha-public-museum/

A Poisonous Interlude

Here's a nifty little critter from this morning:

Arge humeralis, Illinois Beach State Park, Lake Co, IL 6/7/2014

This is Arge humeralis, a sawfly in the family Argidae. While many of the hymenopterans are predators or parasites as larvae, this guy started off as a vegetarian. In fact, he was a very picky eater -- here's his breakfast, lunch, and dinner:

Poison Ivy (Toxicodendron radicans),
Sedge Meadow FP, Lake Co, 10/6/2011

Anyone who's grown up in the Midwest should know this plant. (If not, learn it soon!) This is Poison Ivy, Toxicodendron radicans. It's called Poison Ivy because it produces an oil called urushiol, which in many people can start an allergic reaction resulting in a nasty, itch, weeping rash. It's not fun. (If you're extra-sensitive to Poison Ivy, you might want to consider avoiding Mangos, perhaps even Cashews. They're all in the same family, and Mangos actually produce a small amount of urushiol in their skin.) I can only assume it has the same effect on deer and other mammalian herbivores. The plant is certainly common enough around here. But most such secondary compounds that plants use are primarily aimed at insects rather than vertebrates.

Many of our insects are specialist herbivores as larvae - many moths, for example, only use one or two host plants. Being a specialist means that you can fine-tune your larval digestive enzymes and greatly simplifies your search for a useful place to lay your eggs. Specializing in a plant with effective defenses also seriously reduces your competition. All of these points explain why a specialist individual might be favored within a population, and therefore why so many insects do so.

But there is one potential issue with being a specialist. If your host plant declines, so do you, and if it goes extinct, well...

One potential solution is to periodically make "mistakes" -- after all, biology is always a bit messy. If every once in a while you get an odd individual who lays her eggs in the wrong place, then once in an even longer while that new spot will work -- and now you have an escape hatch if your initial host plant has troubles. Owen-Smith & Novellie predicted something along these lines in 1982. (1) Since then, Poison Ivy Sawflies (that's the common name for A. humeralis) appear to have fulfilled that prediction, according to Benda, et al. (2) , being found feeding on Poisonwood, Metopium toxiferum. (Another member of the Cashew family, Poisonwood also produces urushiol.) Owen-Smith was talking about large herbivores, and the constraints on smaller herbivores are admittedly different, but the same basic logic seems to apply.

This isn't to say that every specialist species manages to find such an out - the trouble with messy processes is that sometimes they don't work. They also tend to be easily outpaced when faced with rapid changes. This is unfortunate, these days, since one things humans are very good at is producing rapid change in a landscape. For every species like an Ailanthus Webworm Moth, we really don't know how many are unable to adapt in time. It's very difficult to say how many species are disappearing when we don't really know how much was out there to begin with. (Incidentally, this is not a call for inaction -- while it's hard to say how many are disappearing, what we do know about the distributions of little critters, especially tropical ones, strongly suggests that our estimates of extinction are biased low rather than high.) The only way to solve this is to get out there and find these critters, which is something that, in many groups, is surprisingly within the reach of amateur naturalists.

(1) Owen-Smith, N., & Novellie, P. (1982). What should a clever ungulate eat?. American Naturalist, 151-178.

 

(2) Benda, N., Possley, J., Powell, D., Buchanan-Mcgrath, C., & Cuda, J. (2012). New host plant record for the poison ivy sawfly, Arge humeralis (Hymenoptera: Argidae), and its performance on two host plant species. Florida Entomologist, 95(2), 529-531.

Of Damsels and Dragons

Spotted a couple of nice critters today:

Blue Dasher (Pachydiplax longipennis),
Illinois Beach SP, Lake Co, IL 6/6/2014

This is a Blue Dasher (Pachydiplax longipennis). It's a common dragonfly around here. (Over most of the country, actually.)

Painted Skimmer (Libellula semifasciata),
Illinois Beach SP, Lake Co, IL 6/6/2014

This one's a Painted Skimmer (Libellula semifasciata). This one's not uncommon in the eastern US, but here in Lake County we're at the very western edge of their range, and this is only the second one I've seen in the county. (The third one showed up at Lyons Woods FP a couple of hours later!)

Dragonflies are serious predators -- they eat other arthropods that they mostly catch in flight, with some of the larger species specializing on tiny gnats and midges. Their large sizes (up to 4.5 inches long in the Giant Darner (Anax walsinghami)), fearless behavior, and incredible flying ability have created legends of all sorts about them, but in fact they're perfectly harmless as long as you don't actually manage to catch one. If you do, you'll likely find out that they've got a pretty strong bite, more than capable of drawing blood from a careless thumb.

If you have dragons, there should be damsels, so here's a couple of beauties:

Slender Spreadwing (Lestes rectangularis),
Spring Bluff FP, Lake Co, IL 6/3/2012

This one's a Slender Spreadwing (Lestes rectangularis).

Rainbow Bluet (Enallagma antennatum),
Raven's Glen FP, Lake Co, IL 6/9/2012

This stunner is a Rainbow Bluet (Enallagma antennatum) from Raven's Glen FP, the only place I've seen them.

Despite the dragon/damsel dynamic that the names suggest, these guys are predators as well. They prey on smaller arthropods (and they're awfully small themselves), while trying not to be dragon food.

As you might expect, dragons are generally larger than damsels, but there is overlap. (Surprisingly, the longest wingspan in the order belongs to a South American damsel (7.5 inches!) (Megaloprepus caerulatus) that preys on spiders.) Better ways to distinguish them involve the eyes and the wings -- most damsels hold their wings back over the body when resting, while dragons hold them straight out from the body. Spreadwing damsels usually hold their wings out, but in a very distinctive V-shape.

The eyes of most dragons touch at the top of the head. In some species, that's only at a point, but in others there's actually a seam running down much of the crown, where the eyes meet. Damsels always have their eyes separated by a distinct crown. Often, there are blue spots on the eyes and crown, sometimes forming a blue bar across the head.

If we have dragons and damsels, we need a knight. Here's the next best thing:

Dragonhunter (Hagenius brevistylus), Nicolet NF, Oconto Co, WI 8/11/2013

This is a Dragonhunter (Hagenius brevistylus), so named because it preys on dragonflies. It is, of course, itself a large dragonfly. It's in the clubtail family, Gomphidae, so named because many of them have broadened segments at the rear of the abdomen forming a club.

If you look closely at this one, you'll see that the eyes don't in fact touch -- they are separated in a manner similar to the damselflies. They do hold the wings out like other dragonflies, and they're stocky like other dragons rather than slender like the damsels, but still... They're a worthwhile reminder, I think, that for all the categorizing we like to do, we're responding to what the critters are doing -- they could care less what we call them, or how we go about figuring out what they are and who they're related to.

A Long-lost Friend on the Landscape

Here's a rather apocalyptic shot:

This is looking over the hill prairie at Gander Mountain Forest Preserve, on April 19. Most of the hill looked black like this, below the tree cover. (The lack of leaves is due to a combination of the date, the cold spring we've had, and the species of trees; oaks leaf out late.)

Halloween Costumes?

One of these doesn't belong:

Castianeira descripta, Waukegan Beach, Lake Co, IL 8/9/2012

Cyrtophorus verrucosus, Van Patten Woods FP, Lake Co, IL 5/28/2014

Crematogaster cerisi, Gander Mt. FP, Lake Co, IL 5/3/2014

Thanasimus dubius, Lyons Woods FP, Lake Co, IL 6/2/2014

Did you catch it? The third one is an ant, specifically Crematogaster cerisi. The others include a spider (Castianeira descripta) and 2 beetles: Cyrtophorus verrucosus and Thanasimus dubius. This resemblance isn't a coincidence -- ant mimics are quite common in the arthropods. In this case, we have three species, all of which evolved their mimicry independently. Apparently ants are fearsome enough critters that they're worth mimicking. (Or maybe they just taste bad.)

These are examples of Batesian mimicry, which is the type most people probably think of: an inoffensive little critter pretending to be a dangerous one, so that everyone will leave them alone. But there's another form of mimicry we often find, called Mullerian mimicry. In this case, a bunch of dangerous or, more often, distasteful critters will all converge on a single appearance. This is quite common among tropical butterflies, including these longwings:

Isabella Longwing (Eueides isabella), St. Louis Zoo, MO, 3/2/2012

Ismenius Longwing (Heliconius ismenius), St. Louis Zoo, MO, 3/2/2012

So what's going on here? Well, it's worth remembering that very few predators are born knowing which butterflies taste bad. They have to learn that lesson somewhere along the way. Once is often enough, but that once is awfully hard on the teacher! By mimicking another distasteful species, you spread that lesson over two species, and reduce the chances of losing your offspring to school.

This point about the cost of teaching is worth remembering for Batesian mimics as well. Batesian mimicry only works if most predators encounter the distasteful species. If a young Blue Jay (for example) runs across tasty Viceroys for a year before he finds a Monarch, he never learns that he should avoid them. This puts Batesian mimics in a rather unenviable position - if they get too common, then they run the risk of losing the benefit of their mimicry. And since many of the models are brightly colored, that means the former mimics are now extraordinarily vulnerable. In the case of the Viceroy, that spells trouble, since Monarch numbers continue to decline. (1)

(1) Texas A&M University. (2014, March 19). Monarch butterfly numbers could be at historic lows this year, study suggests. ScienceDaily. Retrieved June 2, 2014 from www.sciencedaily.com/releases/2014/03/140319114608.htm