I have been writing blog posts for Maryland Grows on a regular basis for a while. To do this, I usually meet with Christa, the blog manager, every 6 months and plan on the topics I will cover over the next few months. When we do this, we seek to cover the needs we see from readers, but sometimes the topics come to us as a result of our discussions. This is exactly what happened for today’s topic. Today, let me tell you the story of how this came to be, and at the same time show you a great free tool available at our (literal) fingertips!
Picture myself and Christa on Zoom, planning dates and topics for the next few months. It is February and it is cold outside. We have been making our way through the upcoming months, thinking of what each one will look and feel like, and what will be growing and buzzing around in each of them. August comes. How is August in Maryland? What do we usually see around? What issues are common in green spaces in August?
I think of August and in my very pollination-biologist-biased way start thinking of the pollinators we see in August… And what comes to me is “butterflies!” I remember writing about butterflies in the past, so maybe butterflies are a bit redundant as a blog topic. However, I don’t remember writing about a specific group of butterflies called “skippers,” which are common in Maryland. So, sure, let’s write about skippers, but what skippers are around in August? As we discuss and try to narrow down the topic, I open this incredible tool I use very regularly to learn about local species, report observations I make, and do research in my lab. This magical incredible tool is called iNaturalist.
So, there I am, opening iNaturalist’s website, and doing a quick search to find out the most common and most abundant skippers we find in Maryland in August. I am doing this, and Christa is intrigued; what am I doing? How am I figuring this out? I decide to share my screen to show her what I’m doing. Christa is amazed. You can do all that with iNaturalist?! The world needs to know! So, there we have it. Our blog topic showed itself to us. Today’s blog will be about what iNaturalist is, how to use it, and what type of information we can share with and learn from it. I hope that this blog will motivate you to start using it as well, and, like me, every time learn something new about species here and elsewhere in the world.
iNaturalist; ever heard of it?
We live in the times of social networks, like Twitter, Instagram, and Facebook… And as it turns out, social networks are really useful to science too! iNaturalist is one of those networks!
iNaturalist is a global social network that allows people to submit, find, and explore biodiversity observations from around the world. What does this mean? This means that through this network, every time a person observes an organism anywhere in the world, they can take a picture of it, upload it to iNaturalist, and then have the network help them identify what it is through its picture (using image recognition software), its location, its date, and the input of other members. This information is then stored in a public database, which can then be explored easily by anybody, including scientists, you, me, kids, conservation agencies, and more! At the end of the day and using all these data, the network can output maps and other information of any species ever added, allowing for the reported localities to be found, and, if the user wants to, visited to try to see the organism in question. Today, iNaturalist has over 5 million users worldwide, with over 109 billion observations of over 380,000 species!
OK. But how does iNaturalist work?
To explain this, let’s come back to my skippers story. I am talking to Christa and want to know what the most abundant skipper in Maryland may be, and whether it is present in August. To do this, I first go to the iNaturalist website (if on a computer; otherwise, I would open the app on my phone). This is what the page looks like.
Raise your hand if you love butterflies. Wow, that’s a lot of hands.
It’s hard to resist the fluttering appeal of butterflies with their delicate wings, zig-zag flight and graceful presence in our gardens. So, why resist? Revel in butterflies’ visits and do more to attract them to your gardens.
This means having flowers blooming from spring to frost. Different butterflies emerge at different times and need fuel to fly.
Flat-topped plants with single flowers provide good landing pads for butterflies. Think zinnias and yarrow or other plants butterflies can easily grasp. Choose native plants such as purple coneflowers, asters and goldenrods that have evolved with native butterflies to provide maximum nutrition.
Butterflies undergo what’s called complete metamorphosis. That means that they are an insect that goes through four distinct life stages: egg, larva, pupa and adult. Host plants provide both a place for adult butterflies to lay their eggs and food for the caterpillars that emerge. So adding host plants helps not one but two butterfly life stages.
Different butterflies need different host plants. For example, dill and parsley are host plants for black swallowtail butterflies while milkweeds host monarch butterflies.
Know that when you plant host plants, they will get munched by hungry butterfly caterpillars. That’s what they’re for! So plant extra in different parts of your garden if you also want harvests for your family.
Butterflies get thirsty, but they have difficulty drinking from deep birdbaths. So add a few rocks to your bird-feeder to make sipping easier.
Like beach-side sunbathers, butterflies bask. They sun themselves to warm their wings to make them flight ready. Set up a suitable sunning area by adding a few flat rocks to your garden.
Ever heard of puddling? That’s what butterflies do when they sip water and nutrients from damp mud or sand. I spied a dozen swallowtails doing this along a nearby creek recently. Magical. Create a puddling area in your garden by keeping a small area of soil damp or by putting damp sand or soil in a shallow bowl.
Protect butterflies by avoiding chemical insecticides in your garden. These chemicals most often can’t distinguish between insect pests and beneficial insects such as butterflies.
Welcome butterflies and other pollinators. Your garden and our community will be richer for it.
Annette Cormany, horticulture educator, University of Maryland Extension – Washington County
The summer is slowly leaving us, with many of us starting to harvest the last wave of vegetables and enjoying the beautiful late summer flowers. At this time of the year, I like to review what happened in the peak of summer and consider what I may want to plant next year, based on what did and did not work this season. I enjoy thinking about how to help pollinators with their favorite plants. I invite you to join me today in exploring how our plant choices are important, using the famous butterfly bush as an example.
Butterfly bushes, a double-edge sword
You may have seen these plants with their blue-purple flower clusters poking out of the bush, and a ton of butterflies and bees visiting the flowers as soon as it gets warm and sunny. The butterfly bush (Buddleja davidii) is a plant species that originates in China. Given its beauty and ease of growth, it was popularized as an ornamental plant first in Europe and later on in other parts of the world.
Its popularity has real reasons: the plant grows fast, flowers very early on in its life cycle, and produces flowers throughout its life span of up to 30 years. The flowers smell good, are very showy and pretty, with large clusters that bloom for several days. Because their flowers need cross-pollination to produce seeds (see how this works in this post), these plants depend on pollinators for reproduction. In their natural habitat, pollination is done mostly by butterflies.
After reading this you may be wondering where I’m trying to go with this post. It seems that these plants are great, so there is not much more to say. If I am considering planting something that will be attractive to pollinators and that is easy to grow, this is a no-brainer, right? Well… maybe not; let me explain.
The problem with plants that are too good to be true is that they usually have a down side. The down side of the butterfly bush in our region is that they are so good that they can “take over” other native plants, which has a number of negative consequences.
Taking over native plants
First, let’s talk a little bit about what I mean by these plants “taking over.” Like all organisms, plants have specific needs to survive in a given place. These needs and abilities evolved over millions of years and are often an evolutionary response to the climatic and soil conditions and the identity of the other organisms living in that community (for example, pathogens, herbivores, pollinators, etc.).
When a foreign species arrives in a new region (like the butterfly bush being introduced in the USA), the fact that they have not evolved in that region can play against them, since they may not tolerate the climate or soils, or may be attacked by parasites or herbivores that they can’t properly defend against. This is why it is often hard to grow species that come from other regions.
Other times, however, not having evolved in the new area can help, especially when most other organisms are not adapted to the species. This means that the new species now does not have to deal with any parasites or herbivores, clearly giving them an advantage over the local species. These advantaged foreign species end up becoming invasive and problematic. Unfortunately, the beautiful butterfly bush is one of these invasive species.
After being introduced into the USA, the butterfly bush is today present and spreading in many regions, including Maryland. This species can reproduce so well, grows so fast, and importantly, has so few herbivores and diseases, that it is able to not only survive, but also spread into new areas at very high speed. Today, the species is listed by the USDA as a weed or noxious weed. It is displacing native flowers as well as agricultural and forest species.
The butterfly bush not only displaces natives by physically occupying the space that native plants would need to survive. The displacement seems to also come in more indirect ways. Because butterfly bushes offer copious amounts of nectar, they become extremely attractive to pollinators, distracting them from other native co-flowering species, and reducing the native’s reproductive success which eventually also harms the native’s populations. This is something that seems to be happening at least in some parts of the USA, suggesting that by favoring this plant in our gardens, we may be indirectly harming the survival and successful reproduction of many of our dear native plants.
You may remember from my previous posts (What should I plant to help pollinators? and Why do pollinators visit flowers?) that plants support pollinators with resources like nectar and pollen. Although the butterfly bush offers abundant nectar to local pollinators, it has been argued that its nectar is too concentrated and could serve as “junk food.” This is likely inaccurate, since studies of nectar concentration in this species indicate that it falls within the usual concentrations seen in other plants preferred by butterflies (watch out for a future post on the super fun topic of nectar concentrations).
Along with this, many people worry that the pollen may not be as nutritious as that of native plants, and from that respect the butterfly bush may be doing more harm than good to the local pollinators. This is currently very much investigated, and even though it seems that the nutrients in its pollen are not equal to those of native plants, they do contain the essential elements the tested pollinators need.
As we covered in other posts, pollinators do not only consume pollen and nectar. In fact, caterpillars of moths and butterflies feed on other plant parts (e.g., the leaves). In our region, the butterfly bush has little to offer in that respect. Because it is not native to our area, few species of caterpillars can feed and develop on this plant. From this perspective, this plant species is not only physically displacing other native plants that are good hosts of local butterflies, it is also unable to provide the food the local caterpillars need… thus finally harming the butterfly population!
But I want a lot of butterflies… what should I plant?
In seasonal regions such as Maryland, nature goes through cycles, with some seasons reserved for growing and reproducing, and others for resting and waiting for conditions to get better. One of the groups of organisms that in my opinion represent clearly those changes in seasons are butterflies, which go through extreme modifications in their bodies and ecologies to closely match the changing seasons. Today’s post is going to explore two beautiful butterfly species that we can find right here in Maryland: the common Black Swallowtail and the beautiful but imperiled Baltimore Checkerspot.
First Things First: The Life Cycle of Butterflies
Before going into details about these butterflies, I think it is important to explain how these organisms develop because their life cycles are usually tightly related to our seasons. Caterpillars have indeed pretty special and fascinating life cycles. In these insects, a female lays eggs on the preferred host plant of the species. This way, the first larva (a tiny caterpillar) that emerges from that egg will not need to move far to feed on its favorite and most nutritious plant.
Once larvae hatch they start feeding on plant material, becoming bigger as they eat. Because insects such as butterflies are covered with a special hard ‘skin’ called an exoskeleton (this is really an external skeleton!) that gives them support and structure, every time the caterpillar gets too big, the exoskeleton becomes too tight (imagine a kid outgrowing a T-shirt). At that point, the caterpillar breaks the old exoskeleton and grows a new larger one in which it can fit.
While going through these ‘changes of skeleton’ (called molts), the caterpillar is able to grow until it is large enough to make their last change: pupation. At this stage, the very large caterpillar is ready to become an adult. For this, the caterpillar will molt a last time and become a pupa, which is the form that builds the cocoon in which the last body changes happen before the adult butterfly emerges.
As one can see, because the life cycle of butterflies has so many stages, there are many chances for things to go wrong during their development, which can also explain some annual fluctuations in butterfly populations. For example, if a wave of particularly cold or hot weather happened during one of the stages at which the caterpillars are sensitive (e.g., pupa, first instars), we may not see many butterflies later in the season. The same is true if there are important disease outbreaks, if predation was particularly high earlier in the season, if the host plants were not as abundant as other years, or if insecticides were applied close to some of the preferred host plants.
Now that we have a better idea of how the life cycle goes, let’s take a look at what our two species do and how they differ in their food preferences, life cycles, and how that affects how we can promote their presence in our surroundings.
Even though it may seem obvious to some, let me start by saying that this species gets its name from the shape of its hind wings, which look like the pointy tails of swallows. Black Swallowtails (Papilio polyxenes)are common butterflies in our region and are present across the whole eastern USA.
In Maryland, this species has between two and three generations per year, with the first generation(s) of a season reaching adulthood within the season, and the last one spending the winter in pupal phase and emerging as an adult the following spring. (Check this other blog to learn more about butterflies in the winter: Where are all the pollinators?)
Like all butterflies, Black Swallowtails are specialized on what they feed. What defines what makes a plant yummy or not to the caterpillars are the chemical compounds the plant carries. In fact, plants have evolved to produce different chemical compounds that protect them against the multitude of herbivores that exist. Black Swallowtails in particular have evolved to tolerate the chemical compounds present in plants of the parsley family (Apiaceae). It is for this reason that these caterpillars can be found in your garden feeding on carrot, parsley, or dill leaves. Adults (butterflies) are usually seen collecting nectar from flowers such as clover, milkweed, and thistles.
Black Swallowtails are currently considered to be a species that is not particularly at extinction risk. However, to maintain their populations it is recommended that open grasslands with plants that serve as caterpillar hosts are present. Interestingly, because they are so common in our area, they can be easily reared indoors, something that is really fun and can be a great summer project for kids (and adults!).
If Maryland has a state dessert, I feel it’s only fair that it also has a state insect! The Maryland state insect is the exquisite Baltimore Checkerspot (Euphydryas phaeton), which was chosen because its colors remind us of those of the Maryland flag. In our area, Baltimore Checkerspots are not as common as Black Swallowtails, and, unlike Swallowtails, have only one generation per year.
Their diets are also significantly more specialized than those of the Swallowtails: young caterpillars feed exclusively on white turtlehead, on which their eggs are laid. While later on in their development they are able to feed at least partially on alternative plants, white turtleheads are required for them to survive the early caterpillar stages.
Finally, unlike most butterflies in our region which spend the winter as pupae, this species spends its winter as a caterpillar and pupates only in the spring. The caterpillars of this species are super cute and they always remind me of the Dust Bunnies of the movie “My friend Totoro”. Adults of this species feed on milkweeds, dogbanes, and wild blackberries.
Unfortunately, even though these beauties are our state insect, they are currently imperiled in our area. The reasons for this have to do with changes in land use, which led to less white turtleheads being available to the caterpillars both because less natural habitats are present and because the deer populations are so large that they eat most of the host plants!
If you would like to try to contribute to these butterflies’ populations, you can plant white turtleheads in your yard, but in particular support conservation actions already happening in Maryland, such as the Baltimore Checkerspot Recovery Team.
By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.
Even though I love the heat of summer, I have to admit that fall makes me happy in a different way. I like the trees that turn into beautiful colors, the crisp air, quiet nights, and the days that slowly become shorter and make me want to drink tea and eat cookies. There is however one thing that makes me a little sad about fall, and it’s that all those beautiful pollinators I love so much are now gone! But are they? Actually, have you ever asked yourself where pollinators go in the fall? Well, thanks for asking — today is your lucky day! In today’s blog post we will talk about what happens to pollinators in the fall, and what we can all do to continue helping them during this quiet time.
When the season reaches an end, pollinators find themselves in a hard spot. They could hopefully collect food (nectar, pollen, etc.) during the spring and summer, but now all the flowers are gone and decisions need to be made if they are to survive until next year. When the season reaches an end, pollinators have basically two options to make sure they or their progeny survive until the next season: migrate for the winter, or stay and protect themselves against the cold.
How to Help Pollinators in the Fall
#1 – Let them go!
Some famous pollinators migrate. You may be familiar with the impressive and beautiful Monarch butterfly migration, which happens every year, and which allows Monarch populations that are far North reach latitudes where the climatic conditions are more benevolent to their survival. Other less famous pollinator migrations are those of hummingbirds, which also migrate to less harsh conditions at the beginning of the fall.
The best thing to do to help migratory pollinators is to help them migrate! This may sound a bit counterintuitive but providing plant resources for migrant pollinators for too long can be a bad idea, because that may make them stay in the region for longer, expose them to parasites for longer, and not reach their final destinations in time.
Let’s take the Monarchs as an example. Monarch caterpillars feed on milkweed, and there are both native and non-native species of milkweed they can develop on (Figure 1).
The native milkweeds naturally start drying out by the end of summer. This changes the chemistry of the plant and “tells” the caterpillars that the end of the season is coming. This is one of the triggers for the caterpillars to start transforming into adult butterflies. Without that trigger from the host plant, the caterpillars continue feeding. This is what happens when they develop on non-native milkweeds that stay green for longer. In fact, caterpillars that develop on those non-native species become adults later in the season, and when they finally emerge, it is too late in the season and they are unable to migrate and make it to the next spring. One of the best ways to protect these migrants is to let them finish their natural cycle and leave in time (I know it’s hard to see them leave!), which in the case of Monarchs requires favoring planting native milkweeds over their non-native counterparts.
#2 – Let them diapause!
Most of the pollinators in our region, however, are adapted to spend the winter right here. Where are they? As I mentioned in another blog post, the vast majority of pollinators in our area are insects. Insects can’t move, fly, or feed if the temperatures are too low. To deal with very low temperatures, insects in temperate regions like ours enter a physiological stage called diapause.
During this stage, the insect physiological rate is reduced and all development is put in a pause until conditions are more favorable. Even though we usually think about these stages when the season comes to an end for us (the fall), it is interesting to note that many of our pollinators reach this stage at the beginning of the summer and they maintain it until the following spring. The practical consequence of this is that if we want to protect pollinators, we don’t just need to provide food for them; we also need to make sure that wherever they decide to spend their diapause is safe from disturbances.
So, how to do this? First, it’s important to realize that each pollinator species enters diapause at different times and places and at different developmental stages (e.g., larva, pupa, adults). Our native bees diapause in nests (solitary or communal), which can be built in different places, depending on the species. The majority of our native bees are ground-nesting bees and they can enter diapause as early as the beginning of the summer and as late as the fall. For nesting, these bees usually prefer loose soils such as those that are sandy or rocky (Figure 2). Making sure that we are not disturbing the ground in places where we see nests will be key for them to survive until the following year. Practically speaking, this means that if you see bees digging holes in the ground of your garden, you may not want to till that part of it.
The second most common place for bee nesting is in cavities. These cavities can be plant twigs and branches, cracks in rocks or walls, or even, in some regions of the world, empty snail shells! If you would like to help these bees in your garden or yards, just leave the remains of all your dry plants through the winter. Chances are that some bees have chosen your dry plants as a place to set their nest (Figure 3). These bees also are the ones that like nesting in homemade bee hotels, and it is really fun to see them emerge early in the spring from the little tubes.
Other bees prefer to build their nest completely above ground. You may have seen little mud “amphoras” or other structures made of little rocks that hang from walls. If you see these nests close to your house, try to not disturb them and keep an eye on them next spring!
Other pollinators, like moths and butterflies, diapause in leaf litter, on wood, or in the ground. They usually do so by enveloping themselves in dry leaves, by digging themselves in the ground, or by attaching their chrysalis onto sticks and branches (Figure 4). To protect these pollinators, you can leave parts of your yard or garden soil undisturbed, keeping at least some of your dry leaves on the soil.
Finally, some moths and butterflies diapause as adults, hiding in wall cracks or small orifices. In these cases, it can be hard to spot them before it’s too late. To avoid that, you can observe around your garden or yard (and around the house) to try to find them. This way, you will know what places you should not disturb when you are doing yard or garden work.
Q: I planted seeds of what I thought was a milkweed (Asclepias). The plants look somewhat like milkweed, but they are close to 4 feet tall with no sign of flower buds to confirm their identity. There are leaf buds at the axils, which I don’t see on other milkweeds. What is this plant? I would like to have milkweed plants for Monarch butterflies.
A: What you have here is not a milkweed. It is Tall White Aster, Symphyotrichum lanceolatum, and the good news is, it is actually what the Monarchs need more at certain times of the year than Asclepias. More on that in a minute, but first, a few notes and a caution about planting milkweeds.
As many people know, milkweeds are essential host plants for Monarch butterfly caterpillars. We commend people for adding milkweeds in their gardens to support butterfly conservation!
Who doesn’t love butterflies? It’s always a lift to see a butterfly or neat-looking moth flutter by on warm sunny days.
At this time of year, butterflies are but a memory. Where do they go and how do they survive our winters?
Most people are probably aware of the monarch butterfly (Danaus plexippus) and their incredible migration to the warmth of Mexico each year. There has been much discussion of their falling populations due to overwintering habitat destruction and their singular need for milkweed (Asclepias sp.) for egg laying and caterpillar food in our area during the growing season. With good habitat and plenty of milkweed, they can grow into the beautiful adults which make that long trek of 3,000 (!) miles to more sunshine. (Sounds pretty good right now, doesn’t it?)