The Sophistication of Ticks

Note: This program first aired August 1, 2015.

Ticks seem to be everywhere this season, in the woods where I walk, on my dogs and cats, crawling up my pant legs, and this past spring, all over Facebook-everyone was posting about the spring emergence of the ticks. And I get it, Lyme (not to mention all the other tick borne diseases) is sometimes difficult to treat and can be life altering for some of sufferers. But this isn’t a program about health or disease, it’s about the natural world, and for better or worse, ticks are part of that world.

Ticks are arthropods, a group of animals that is characterized by having a chitinous exoskeleton and jointed legs. Insects and crustaceans are classes of arthropods we are all familiar with. Ticks are in the class Arachnida with spiders and mites, a sub group of arthropds that typically have 8 legs and specialized mouth appendages. In reading up on ticks I learned some things that are fascinating, and so even though they are one of the most hated groups of animals around, I want to share what I found out.

Ticks, like many insects, undergo incomplete metamorphism, which means that they hatch from an egg into a form that is similar to the adult, usually just smaller and sometimes with less well developed appendages or body parts. For example the deer ticks we worry about so much here in Maine have only 6 legs in this newly hatched stage. Typically this stage is called larval, though you shouldn’t confuse it with the larval stage of an insect like a butterfly that undergoes complete metamorphism. In those organisms “larva” means caterpillar or grub or maggot, something that looks nothing like the adult. Baby or larval ticks look like tiny ticks, and they feed on the same thing as adults; blood. Tiny larval ticks require a blood meal before they can grow into the next stage of life, once they have eaten, they molt their exoskeleton and emerge as a nymph. Nymph ticks often look just like adults, only smaller. They also need a blood meal in order to molt and grow into the last stage of life, the adult. The job of the adult tick is to mate, and only the female needs a blood meal, so that she can lay her eggs, and the cycle starts over. So, egg hatches, larvae, feeding, nymph, feeding, adult, feeding; they eat three times (and only three times) during their lives which can last over a year here in Maine.

Three times in a year and a half, that isn’t much food, for that much time. Each time they bite they have to get enough food for months. How they do it is really interesting. We all know that ticks embed themselves into the skin of their victim, staying attached for days while they suck out the blood they need to further their life cycle. Ticks have specialized mouth parts that work in tandem, one part ratchets while the other part drives deeper into the skin. These parts are lined with reversed direction barbs, so they can’t simply slide back out. Once the mouth parts are fully embedded, no energy is required for the tick to stay there and feed.

Ticks are very small animals, yet they need to get enough food to sustain them for months from just one feeding. If you have ever seen an engorged tick on your dog or cat, all shiny and gray and swollen, you know that ticks have an abdomen that can stretch to hold a large volume of blood. Even more remarkable though is the level of sophistication the ticks have when feeding. As the ingest blood from their host, it is immediately digested and separated out. Ticks keep the red blood cells, apparently the most nutritious fraction of blood. All the rest, the plasma fluid, salts, other blood cells, gets excreted back into the host’s body. So the ticks suck your blood, take only the best parts, and spit the rest back out, thus concentrating their meal. That is how they are able to feed once and live for many months on that one meal. And that is why, for animals that have a high tick burden, anemia can become a real problem.

Detested, persecuted, hated; ticks get a bad rap in the animal world. They are only doing what we all are though, living the only life they know how to lead, fulfilling their biological destiny along the way.

References: 

About ticks and climate change http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2582486/

Tree of Life site for Arachnids http://tolweb.org/Arachnida

Comprehensive list of ticks in Maine from Maine Medical Center Research Institute: http://www.mmcri.org/home/webSubContent.php?list=webcontentlive&id=108&catID=4&subCatID=19

A Maine based company with lots of info on their website: http://www.mainelyticks.com/familysafety-lifecycle.html

Tick mouthparts: http://www.nytimes.com/2013/10/30/science/earth/how-does-a-tick-do-its-dirty-work-research-video-offers-a-clue.html?_r=0

Thank you Ed Yong for citing this article (though no one seems to have looked at how they detatch themselves and get those amazing barbed mouthparts out of your skin): http://rspb.royalsocietypublishing.org/content/280/1773/20131758

Moose, ticks and anemia http://www.nwf.org/Wildlife/Threats-to-Wildlife/Global-Warming/Effects-on-Wildlife-and-Habitat/Moose.aspx

Beloved Summer Insects: Deerflies

Note: This program first aired on August 2, 2014.

This week’s show is dedicated to WERU’s own News Editor, Amy Browne. I happen to know, from social media, just how she feels about the animal we are going to talk about today, though I also know from experience, she’s not alone.

The animal, the bane of existence for so many people, and so many companion animals this time of year, is the deer fly. The common name Deer fly refers to a group of animals in the genus Chrysops, of which there are about 100 species in North America alone. Deer flies are in the insect order Diptera, with all the other flies, in this case their common name is not a trick. It is the females that cause us so much grief. They require a blood meal from a vertebrate to ensure viability of their eggs. Males sip nectar from flowers, (like male mosquitos) for their sustenance. Deer flies (and their closely related bretheren Horse flies) are universally referred to in the literature as having “knife like” mouth parts. They achieve the required blood meal by slashing away at the flesh of the victim, causing a generalized bleeding, which they then slop up with their “sponge like” mouth parts. This part of the story you know well, if you spend any time outside in Maine in the summer.

I wanted to know more about these extremely annoying creatures, so I dug in a bit to see what I could find. And it turns out it is much as I suspected. They are hydrobionts, meaning they need wet areas in which to breed. The females, after their blood meal, lay their eggs on the underside of leaves in the understory or in swamp areas, above damp or wet ground. When the eggs hatch the larvae that emerge drop into the wet ground below and burrow in, living on detritus or as predators of smaller insects and worms. The larvae are active all winter, below the frost line apparently, and after feeding all winter they apparently pupate in early spring for a few weeks. The adults emerge in summer and live from one to two months, tormenting me and Amy Browne and our dogs, and anyone else foolish enough to be outside in wet areas when the temperature is warm enough. One of the sources I found indicated a minimum temperature range of 72 degrees F, but I know that to be incorrect, at least for the deer flies here in Maine. If I can get out before the temperature hits 60 degrees I know I will miss most of them, but above that, they are good to go. They are also primarily visual predators, attracted first and foremost to dark objects that move. If I wear a light colored shirt on my morning run I am much less bothered. My large black thin coated dog however, has no such choice. Sources say that scent and other biological cues like carbon dioxide are also attractants, but my experience leads me to believe the idea that they are primarily visual. It seems that their job in this world is to bite, and bite well, much to our chagrin.

Isn’t that the job of every animal? Every organism? To do whatever it can to carry on and pass on its genes? It is easy to disparage a biting insect that bothers us for one to two months a year, but we have to remember that everything has a job in an ecosystem. The job of many of the deer fly eggs is to get parasitized by wasps. The job of many deer fly larvae is to get invaded by bacteria and fungus and other microbial parasites. The job of many an adult deer fly is to get eaten by swallows and flycatchers and predatory insects like dragon flies and hornets. The job of the ones that survive is to reproduce, and to do that, they need us, or our dogs, or our livestock, or more likely, the large vertebrates that populate the north woods.

No body likes hanging out with deer flies. But all the same, I prefer a world where they exist, a world as full as it can be with as many different kinds of organisms as possible, a world rich and damp and squirming with life. That is truly the point of it all, and we can’t do it without the biters and scratcher anymore than we can do without the cute furry babies and the fluffy little birds. They all count, every last knife like mouthpart wielding one.

References:

More good stuff from Bug Guide: http://bugguide.net/node/view/11387/bgpage

Here’s a whole bulletin about them from the Maine Forest Service: http://library.umaine.edu/MaineAES/TechnicalBulletin/tb160.pdf

Good photos: http://entnemdept.ifas.ufl.edu/creatures/livestock/deer_fly.htm

Butterfly Life Cycle, More Than Just Egg, Larva, Pupa and Adult

Note: This program first aired on July 26, 2014.

A few weeks ago, I mentioned some of the butterflies I’ve been seeing around; right now its all fritillaries and sulphurs, earlier this summer is was Swallowtails, the Mourning Cloaks were earlier still this spring. Later in the summer I hope to see some Monarchs. Have you ever wondered why some butterflies are around at certain times but not others? Why are the Mourning Cloaks the first ones here in the spring, and then they disappear? Why are we seeing the fritillaries in such abundance now? Have you even noticed that there is a pattern to the appearance of different butterflies? Believe it or not, it’s not random happenstance. The answer is due to the fact that although we’ve all watched the Discovery Channel and think we have the butterfly life cycle down pat, it’s much more complicated and interesting than egg, larva, pupa and adult.

The truth is, butterflies are short lived creatures that come in seasons based on their life histories. Though it is hard to remember now in the thick of the heat of summer, the main obstacle to all arthropods is the cold of winter. Being primarily ectothermic or at the mercy of the external environment for temperatures favorable for metabolism and activity means that most insects have a difficult time being active in the winter here in Maine. The question facing butterflies, and all arthropods, is how to deal with winter. There are two main choices, the same ones we humans face, you can stick it out here in some kind of overwintering dormancy, or you can get the heck out of Dodge and migrate to warmer climes. 

Migration is not the most common butterfly strategy for dealing with winter, and it’s easy to speculate on why. First, only the adults could possibly travel far enough, how much ground can a caterpillar really cover? Secondly adults don’t tend to live very long, we’re talking about live spans of days to weeks in most cases. Thirdly, and this is pure bias and subjectivity on my part, butterflies seem so fragile, so wispy. I can barely believe that tiny birds migrate successfully thousands of miles, but something as insubstantial as a butterfly? The best known of the migrating butterflies is of course the Monarch, and the details of just how they do it is still a huge mystery. What is known is that it takes multiple generations for them to complete the migration. The ones that leave here are not the same ones that return the next year. The ones that return are the great or great great grandchildren of last year’s butterflies.

So then, migration happens but is uncommon, and the timing of the return of the migrators depends on many factors, weather and conditions not only here but everywhere along their route, which can be thousands of miles. For those butterflies that stay here year round, the majority of them, they face a choice as well. We know that the basic butterfly life cycle includes an egg, a larval stage, a pupa stage and an adult stage. Which stage is the best one in which to wait out the winter? If you thought there was a clear cut answer to that, you haven’t spent much time studying evolution. The answer is of course, all of them. Different species have evolved different tactics for dealing with winter, mainly guided by coevolution with their host plant, the thing the larva or “eating stage” of the insect, lives on.

Mourning Cloaks are the first butterflies we see in the spring, and the reason for this is that they over winter as adults. They hide out under bark or in the leaf litter, emerge on the first warm days in early spring, mate and die. We see them again in the fall when the new generation emerges from a period of summer dormancy, fattens up on nectar and prepares to over winter. The Swallowtails we see in June by contrast, after the Mourning Cloaks are all gone, have over wintered as pupae, often attached to the trunks of trees. Their larvae spend the summer feeding on the leaves of various deciduous trees, and the last instar forms the chrystalis in time for winter’s cold. The fritillaries flying about now started out last year as an egg laid in late summer, near a patch of dead violets. The egg hatched and the tiny larva that emerged, the first instar, is what over wintered, without eating. This spring, when the violets emerged as a spring wild flower, the fritillary larvae were already there, ready to start feeding. Each of these butterfly species positions itself to be ready to make full use of its favorite larval food, and these plant foods in turn, have their own seasons, thus so do the butterflies.

Watch nature long enough and it becomes a giant game of connect the dots. The more you play, the more you learn, and the more you realize there is to learn. Play long enough, and you realize all the dots are connected.

References:

Canadian reference on Mourning Cloaks http://www.naturenorth.com/spring/bug/mcloak/Fmcloak.html

Butterflies

 Note: This program first aired on June 21, 2014.

Summer seems like it is finally here and I have been enjoying the good weather outside as much as possible. It seems to me that there is an abundance of butterflies this year, particularly the large yellow and black Swallowtail butterflies. And earlier this spring, I noticed many Mourning Cloak butterflies around as well. It could be that I am simply paying more attention, so in the absence of hard data don’t consider this a trend. My life has led me to butterflies, which means I am seeing and appreciating more of them during the fleeing time they are here, that is all.

Butterflies under go what is called complete metamorphism, in that they have four fully differentiated stages of their development: egg, larva, though in the case of butterflies and moths the larva is by definition called a caterpillar, pupa and adult. Each of these forms is markedly different from the others, and this difference is one of the reasons we find insects so remarkable. The adult female lays the egg, typically one of hundreds of eggs, on or near an appropriate host plant for the soon to hatch caterpillar. The host plant is important, because as soon as the egg hatches, the caterpillar begins to eat, and it is usually pretty picky about what it likes (like so many kids). The caterpillar’s job is to eat and grow, which they do quite well, though most of them get eaten themselves, either directly by birds and other small hungry animals, or worse, by internal parasites. Many many other insects including certain flies and wasps use caterpillars as mobile feeding stations for their young. Eggs are either deposited directly into the caterpillar, or laid on host plant material, where the very hungry caterpillar unsuspectingly ingests the parasite egg. Once inside the caterpillar, the parasite egg hatches and the larva develops inside the caterpillar. Recall that the job of an insect larva is to eat. One source I read remarked casually that the parasitizing larva carefully eats the caterpillar alive from the inside, saving the vital organs for last, to keep the host caterpillar alive longer.  If the caterpillar doesn’t get eaten or parasitized, it will grow. We think of caterpillars as soft and squishy, but really they must follow the same rules as all other arthropods. Arthropods have exoskeletons, and must molt, or shed their old exoskelton for a new larger one when they grow. Caterpillars do the same, shedding their tough outer skin. Each time they do this, they get bigger, and may even change color or shape, each version of the caterpillar is called an instar, for example you might identify a caterpillar as “the third instar of the eastern Tiger Swallowtail”. During the last molt or shedding of caterpillar skin, what emerges is not another caterpillar, but the pupa. This stage of the life cycle is often referred to as a resting stage, but really it is anything but. It is true that the pupa (contained in a chrystalis in butterflies and which occurs in the cocoon in moths) is usually immobile, but inside the protective exterior, the entire body of the caterpillar breaks down and is rearranged into an adult. The adult body structures form from just a few cells, sort of like stem cells, called imaginal discs,  that originate in the insect egg, and are carried dormant inside the caterpillar all along. Just like us. A part of who you are comes from your maternal grandmother’s health and well being, as one of the eggs that became you developed in the embryo that became your mother inside your grandmother’s womb. Other bits of you come from your father, who continuously generates new genetic material throughout his life. As humans we take those bits of DNA and we develop, we grow, we age, we come into our fully articulated being, and we wonder where this person we’ve become came from. Just like the butterfly, emerging after so much work and shape shifting, we have to remember, we were there all along.

References:

Many online references exist for butterflies, none better than Bug Guide http://bugguide.net/node/view/81

A link from the Bug Guide site, to a California lepidopterist: http://mamba.bio.uci.edu/~pjbryant/biodiv/lepidopt/GettingIntoButterflies.htm

Bug Guide Mourning Cloak page: http://bugguide.net/node/view/3188

Good stuff on insect metamorphism from Scientific American: http://www.scientificamerican.com/article/insect-metamorphosis-evolution/

And specifically butterflies and moths: http://www.scientificamerican.com/article/caterpillar-butterfly-metamorphosis-explainer/

Frass Happens

Note: This program first aired on September 14, 2013.

I’ve been noticing lately, and maybe you have been too, what seems like an awful lot of insect frass around. Frass on my porch, my roof, my adirondack chairs. Put up a tent or a tarp, and as long as it is underneath some trees, it will be covered with the stuff. What this tells me is that there are a lot of insects in the trees, specifically, larval insects, and they are apparently doing a lot of eating. Frass is indeed linked to food, because frass, my friends, is insect poo. Just like you and me, the more they eat, the more they excrete.

Summer is the time of the insect, the warm temperatures bring plentiful food sources, and insects have evolved to take full advantage of this brief window. The insect life cycle is a fascinating one; I, for one, can’t stop thinking about how cool it is. There are three main paths to becoming an adult insect. The first is simple metamorphism, and it has a couple of sub categories. Of those, the first is gradual metamorphism (also called paurometabolous (small or slight change) metamorphism). The egg is laid by an adult, and what hatches out of the egg is essentially a tiny little adult, that eats and grows and molts its exoskeleton and grows some more, molting and growing until it gets big enough to be sexually reproductive and is considered and adult. This is the M.O. of grass hoppers, for example. The other form of simple metamorphosis is incomplete or hemimetabolous (half change) metamorphism. An egg is laid by an adult insect, and out of the egg hatches a juvenile stage that looks different than the adult. In this immature stage they are called nymphs or naiads and are aquatic. This nymph eats and grows, molting its exoskeleton, until its last molt, when what comes out is not another nymph but an adult insect. Dragon flies grow this way.

The second category is complete metamorphism also called homometabolous (whole change) metamorphisman. An adult lays an egg, from which hatches a larvae, (caterpillar, grub etc) which grows through several different stages, called instars, molting an exoskeleton or outer skin as it passes from one instar to the next. Then the larvae turns into a pupa, the stage of true metamorphosis, during which the cells of the insects body completely rearrange themselves. It is often referred to as a resting stage in the literature, but the insect is only appearing to rest. Inside there is a major transformation going on. This is the cocoon stage of the butterfly, as an example. From the pupa emerges the adult, totally and utterly reconfigured from the larvae.

Complete metamorphism is by far the most popular means of insect growth, found in approximately 10 times as many species as incomplete metamorphism. There are some distinct advantages to having such wide variation in the different stages of growth, and the first is division of labor. Ken Kaufman in his guide to insects refers to each stage of the insect as having a different job, and the analogy is a good one. The egg has it the easiest, it simply has to incubate. The larvae are “eating machines”, their job is to get as much nutrition as they can because the metamorphosis that occurs in the pupa stage is so incredibly hard and energy consuming. The adults may or may not eat, but their main job is to reproduce. Typically the larvae also live in different habitats than the adults (sometimes really different habitats, for example the larvae of black flies and mosquitos are totally aquatic, they live under water). This can reduce intergenerational competition for resources, always a good thing.

So it is larvae in the trees that is making all that frass, larvae doing all the work of eating, for many of these caterpillars turn into moths and butterflies that don’t eat at all. It’s a division of labor so stark it is hard to imagine. Its also perfectly synched to the rhythm of nature, those caterpillars, grown fat on summer’s greenery, will pupate and spend the long winter slowly rearranging their cells, preparing to emerge in the spring as new beings. It makes me feel crass and ill fitted in comparison. As the days grow shorter, we would do well follow their example, respecting the season and using what it offers, a break from the frenetic frass making of summer, to renew and reorganize ourselves as well.

References:

www.bugguide.net The definitive internet insect resource, email in your photos to get identifications from an online community of bug nerds.

Ken Kaufman’s Field Guide to Insects of North America 2007 Houghton Mifflin, I love this book, it (like all Kaufman guides) uses actual photographs, but at the same time manages not to be too creepy.

Freeman, Quillin, Allison Biological Science 5th ed. 2014, Pearson
Most any modern biology textbook will give you some good basic information about Arthropods

Nice site from the West Virginia University Extention service, clarifying  different types of metamorphosis,
http://www.caf.wvu.edu/~forage/insect_m_morph.htm