insects

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Vacant Lots as Habitat for Insects

Urban areas are increasingly being studied for their potential to help conserve biodiversity and provide habitat for numerous plants and animals. Despite the harsh conditions of the built environment, organisms of all kinds are able to survive in our cities, and as we find ways to make these spaces more hospitable for them, cities actually have great potential for species conservation, even for species that are rare, threatened, or specialized. One obvious way to accomplish this is to manage our yards, parks, and gardens as habitat, such as planting flower strips for pollinators. Another way, perhaps overlooked at times, is to manage and maintain vacant lots as habitat. Every urban area has some degree of vacant land that for one reason or another has not been developed, or that once was developed but has since been bulldozed or abandoned. Spontaneous vegetation quickly moves in to occupy these sites, and while some may see them as eyesores, their potential for providing habitat for an untold number of plants and animals is substantial.

In cities that are growing – like Boise, Idaho – vacant and abandoned lots are disappearing quickly as development strives to keep up with population growth. My first Weeds of Boise post took place at an abandoned Pizza Hut, which has since been demolished and is now the future site of a large building (see photo below). This is happening all over the city – the City of Trees is looking more like the City of Cranes these days. On the other hand, cities that are shrinking due to economic downturn, loss of industry, and other factors, have an increasing number of vacant lots, which offers the opportunity not only to maintain these lots as habitat, but also to carry out research that will help us understand how these locations can be best managed for species conservation.

Abandoned Pizza Hut Lot Now Under Construction

Cleveland, Ohio is one example of a “shrinking city.” Due to significant population decline, Cleveland has a growing number of vacant lots, many of which are maintained by the City of Cleveland Land Bank. For researchers at The Ohio State University, all of this vacant land presents an opportunity to study, among other things, urban biodiversity. Hence, the Cleveland Pocket Prairie Project was born. By assigning different management treatments to groups of vacant lots and observing the differences between each treatment, researchers can help determine the best strategies for managing vacant lots, particularly when it comes to biological conservation. One of the major focuses of the Cleveland Pocket Prairie Project is to determine how vacant land can provide habitat for insects and other arthropods.

In a study published in Sustainability (2018), researchers in Cleveland compared the species richness and abundance of bees found on vacant lots to those found on urban farms. Bee collections were made three times a year over a three year period. Of the more 2733 bees collected, researchers identified 98 total species representing 5 different families. The vast majority of the species were native to the area. Significantly more bees were found in vacant lots compared to urban farms. In both vacant lots and urban farms, the total number of ground nesting bees decreased as the proportion of impervious surfaces near the study sites increased. Plants that received the most bee visits on the urban farms during the study period were common milkweed (Asclepias syriaca), chives (Allium schoenoprasum), and squash (Cucurbita pepo); while the top three plants with the most bee visits on vacant lots were red clover (Trifolium pratense), white clover (Trifolium repens), and Queen Anne’s lace (Daucus carota).

ground nesting bee (photo credit: Sierra Laverty)

Bee communities differed between vacant lots and urban farms: 29 of the 98 total species were seen only in vacant lots, while 14 species were seen only at urban farms. Most of the bees collected in this study were ground nesting species, and researchers suspect the reason more bees were found on vacant lots compared to urban farms is that farms experience frequent soil disturbance in the form of tillage, weeding, mulching, and irrigation, while vacant lots generally do not. The researchers conclude that their study “adds to the growing body of literature advocating for the maintenance of minimally-managed vacant lot habitats as a conservation resource.” Vacant land that is “surrounded locally by high concentrations of impervious surface,” however, may not be the most suitable location to carry out conservation efforts.

In a study published in Urban Ecosystems (2020), researchers in Cleveland looked at the species richness and abundance of lady beetles in vacant lots. They were particularly interested in the potential that vacant lots may have in providing habitat for lady beetles that are native to the region. The study consisted of 32 vacant lots, each assigned one of four habitat treatments: control (seeded with turfgrass and mowed monthly), meadow (seeded with turfgrass and mowed annually), low-diversity prairie (seeded with three species of prairie grasses and four species of native prairie forbs), and high-diversity prairie (seeded with three species of prairie grasses and sixteen species of native prairie forbs). The two prairie treatments were mown annually. The majority of the nearly 3000 lady beetles captured across all of the plots over a two-year study period were exotic (introduced) species. Sixteen species total were collected: four exotic and twelve native.

The researchers predicted that the lots seeded with prairie plants native to the region would support a higher abundance of native lady beetles than those composed of turfgrass, especially those that are frequently mown. Surprisingly, a similar abundance and species richness of both native and exotic lady beetles were found across all treatments. What appeared to be important for native lady beetle abundance were vegetation features like bloom abundance, height, and biomass. The surrounding environment also matters. As the researchers put it, “vacant lots embedded in landscapes dominated by impervious surface and with a high degree of habitat isolation were less suitable habitats” – a similar conclusion to that made in the bee study.

Brachiacantha ursina (photo credit: Wikimedia Commons / NY State IPM Program at Cornell University)

The most abundant native lady beetle collected in the study was the ursine spurleg lady beetle (Brachiacantha ursina). The larvae of this beetle “infiltrate the nests of Lasius ants,” which is “one of the most common genera of ants found in urban environments.” Researchers posit that the abundance of B. ursina reflects the habitat preferences of ants in the Lasius genus. Several species of lady beetles native to the region are experiencing significant population declines, and the researchers were disappointed to find that none of the most rare species were collected during their study period. However, it was promising to find that “pollen and nectar provided by both seeded native and naturally occurring weedy plants” appeared to be important food sources for native lady beetles.

Both studies indicate that vacant lots can be important locations for habitat conservation in urban areas, particularly when they are part of a larger collection of greenspaces. In combination with managing our yards, parks, and urban farms as quality habitat for plants and animals, conserving vacant lots that consist of diverse vegetation (both planted and spontaneous) can help support insect populations within our cities.

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The Life Cycle of a Sunflower Stem Weevil

Last summer I came across a downy woodpecker hammering away at the stalk of a sunflower. I wondered what it was going after, and so I split open a stalk lengthwise to find the center of the stem hollowed out and several small larvae squirming through the debris left behind. A quick internet search later and I was learning about sunflower stem weevils, specifically Cylindrocopturus adspersus, which seems to be the species getting the most attention online and the stem-dwelling weevil that commercial sunflower growers seem most concerned about.

However, the range of sunflower stem weevil doesn’t appear to extend into Idaho, and so this is not likely to be the larvae I was seeing. There are other weevil species whose larvae can be found inside the stems of sunflowers (The sunflower I was observing was Helianthus annuus. I wasn’t specific about naming a particular species because it is my understanding that these weevils can be found on a variety of different Helianthus species., such as the cocklebur weevil (which is found in Idaho), but since larvae can be difficult to identify, I’ll wait to confirm the identity until I hear from an expert, find an adult weevil, and/or raise the larvae in captivity and see what it turns into. If and when that happens, I’ll be sure to update you. Until then, I present to you the life cycle of a sunflower stem weevil, which is still quite interesting, even if it’s not the species I found inside my sunflower stalks. And to be clear, the sunflower I observed was Helianthus annuus; however, the weevils I refer to in this post can be found on a number of different Helianthus species and related genera.

Sunflower stem weevils are in the family Curculionidae, which is the snout and bark beetle family. There are tens of thousands of species of weevils, a handful of which interact with sunflowers (plants in the genus Helianthus). Some weevil species eat the seeds, others eat the leaves, some are root feeders, while others are stem feeders. Depending on the life stage of a particular weevil species, it may consume multiple parts of a sunflower. Another interesting weevil is the sunflower headclipping weevil, which you can read about at The Prairie Ecologist.

Adult sunflower stem weevils are about 3/16 inch (4-5 mm) long and somewhat egg or oval shaped. They are grayish-brown with white spots. Their eyes, antennae, and snout are black, and their snout is short, curved, and held beneath the head. As adults, they can be found on sunflowers and sunflower relatives eating the leaves. However, they are not easily found. Their size, for one, makes them difficult to see, and they also move to the opposite sides of leaves and stems when disturbed, sometimes dropping to the ground as a threat approaches. You can see images of them on BugGuide.

unidentified larva in a sunflower stem

The larvae of sunflower stem weevils are about a quarter of a inch long and creamy white with a small, brown head capsule. They feed in the vascular tissue of sunflower stalks during the summer. In the fall, they migrate to the base of the stalks and create chambers in the woody tissue of the stalks and root crowns for overwintering.

Sunflower stem weevils have a single generation per year. After overwintering as larvae in the base of last year’s sunflowers, they pupate and emerge as adults in late spring or early summer. They find young sunflower plants and begin feeding on the leaves. After about 2-4 weeks, the weevils mate and lay eggs just beneath the epidermis of sunflower stems, usually in the stalk just below the cotyledon leaves. The eggs hatch a short time later and begin feeding in the stem until it’s time to overwinter.

the life cycle of a sunflower stem weevil

The damage caused by sunflower stem weevils is generally only a problem on sunflower farms, and only when weevils are found in high enough numbers to cause significant yield losses. Damage to leaves by the adults isn’t usually a concern. On the other hand, as the larvae tunnel through the stem, they can cause the plant to lodge (i.e. fall over prematurely), which is a problem particularly when the plants are machine harvested. Sunflower stem weevils can also introduce and help spread a fungus that causes black stem rot.

Read More About Sunflower Stem Weevil and Other Insect Pests of Sunflowers:

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Flowers Strips Bring All the Pollinators to the Yard

The longer I garden the more I gravitate towards creating habitats for creatures that rely on plants for survival. I’ve always been more interested in functional gardens rather than gardens that are simply “plants as furniture” (as Sierra likes to say) – a manicured, weed-free lawn, a few shrubs shaped into gumdrops, sterile flowers for color – and that interest has grown into a way of life. A garden should be more than just something nice to look at, and for those of us who’ve embraced the “messy ecosystems” approach, what’s considered “nice to look at” has shifted dramatically.

Thankfully, I’m not alone in this thinking. Gardens focused on pollinators, birds, habitats, native plants, etc. seem to be gaining in popularity. The question is, is it making a difference? At least one study, referred to below, seems to suggest that it is. And as more gardens like these are planted and more studies like this are done, perhaps we will get a clearer picture of their impact.

In 2017, eight 1000 square meter flower strips were planted in Munich, Germany. The sites had previously been lawn or “roadside greenery,” according to the report published in the Journal of Hymenoptera Research (2020). An additional flower strip, planted in 2015, was included in the study. Over the next year, an inventory of the number of bee species found in these nine flower strips was taken and compared both to the number of bee species that had been recorded in Munich since 1795 (324 species) and the number of bee species recorded in the 20 years prior to the planting of the flower strips (232 species).

In just a year’s time, these newly planted flower strips quickly attracted a surprising number of bees. The researchers identified 68 different species (which is 21% and 29% of the two categories of previously recorded species). As they had expected, most of the bees they identified were common, non-threatened, generalist species; however, they were surprised to also find several species that specialize on pollen from specific groups of plants. Future studies are needed to determine whether or not such flower strips help increase the populations of pollinators in the city, but it seems clear that they are a simple way to increase the amount of food for pollinators, if nothing else.

But perhaps these results shouldn’t be that surprising. Urban areas are not necessarily the biodiversity wastelands that the term “concrete jungle” seems to imply. Though fragmented and not always ideal, plenty of wildlife habitat can be found within a city. In his book, Pollinators and Pollination, Jeff Ollerton lists a number of studies that have been carried out in cities across the world documenting an impressive number of pollinating insects living within their borders [see this report in Conservation Biology (2017), for example]. As Ollerton writes, these studies “show that urbanization does not mean the total loss of pollinator diversity, and may in fact enhance it.” After all, “many of us city dwellers see every day, nature finds a home, a habitat, a place to thrive, wherever it will.”

In a chapter entitled, “The Significance of Gardens,” Ollerton continues to explore the ways in which cities can host a wide variety of flower visiting insects and birds. “Planted patches” don’t necessarily need to be managed as pollinator gardens in order to provide resources for these creatures, nor do all of the plants need to be native to the region to be effective. Rather, diversity in flower structure and timing seems to be key; “floral diversity always correlates with pollinator diversity regardless of the origin of the plants,” Ollerton writes in reference to pollination studies performed in British cities. The more “planted patches,” the better, as “a large and continuous floral display in gardens is the only way to maximize pollinator abundance and diversity.” Add to that, “if you allow some areas to become unmanaged, provide other suitable nesting sites or areas for food plants, and other resources that they need, a thriving oasis for pollinators can be created in any plot.”

ground nesting bee emerging from burrow

Bees and other pollinating insects are finding ways to live within our cities. There is no need to go to the lengths that I like to go in order to help them out. Simply adding a few more flowering plants to your yard, balcony, or patio can do the trick. Eliminating or limiting the use of pesticides and creating spaces for nesting sites are among other things you can do. Learning about specific pollinators and their needs doesn’t hurt either. The continued existence of these creatures is critical to life on earth, and this is one important issue where even simple actions can make a real difference.

Check out the linktree for various ways to follow and support Awkward Botany.

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Camel Crickets and the Dust Seeds of Parasitic Plants

A common way for plants to disperse their seeds is to entice animals to eat their seed-bearing fruits – a strategy known as endozoochory. Undigested seeds have the potential to travel long distances in the belly of an animal, and when they are finally deposited, a bit of fertilizer joins them. Discussions surrounding this method of seed dispersal usually have birds and mammals playing the starring roles – vertebrates, in other words. But what about invertebrates like insects? Do they have a role to play in transporting seeds within themselves?

Certain insects are absolutely important in the dispersal of seeds, particularly ants. But ants aren’t known to eat fruits and then poop out seeds. Instead they carry seeds to new locations, and some of these seeds go on to grow into new plants. In certain cases there is an elaisome attached to the seed, which is a nutritious treat that ants are particularly interested in eating. Elaisomes or arils have also been known to attract other insects like wasps and crickets, which may then become agents of seed dispersal. But endozoochory in insects, at first, seems unlikely. How would seeds survive not being crushed by an insect’s mandibles or otherwise destroyed in the digestion process?

camel crickets eating fruits of parasitic plants (via New Phytologist)

While observing parasitic plants in Japan, Kenji Suetsugu wanted to know how their seeds were dispersed. Many parasitic plants rely on wind dispersal, thus their seeds are minuscule, dust-like, and often winged. However, the seeds of the plants Suetsugu was observing, while tiny, were housed in fleshy fruits that don’t split open when ripe (i.e. indehiscent). This isn’t particularly unusual as other species of parasitic plants are known to have similar fruits, and Suetsugu was aware of studies that found rodents to be potential seed disperers for one species, birds to be dispersers of another, and even one instance of beetle endozoochory in a parasitic plant with fleshy, indehiscent fruit. With this in mind, he set out to identify the seed dispersers in his study.

Suetsugu observed three achlorophyllous, holoparisitic plants – Yoania amagiensis, Monotropastrum humile, and Phacellanthus tubiflorus. While their lifestyles are similar, they are not at all closely related and represent three different families (Orchidaceae,  Ericaceae, and Orobanchaceae respectively). All of these plants grow very low to the ground in deep shade below the canopy of trees. Air movement is at a minimum at their level, so seed dispersal by wind is not likely to be very effective. Using remote cameras, Suetsugu captured dozens of hours of footage and found camel crickets and ground beetles to be the main consumers of the fruits, with camel crickets being “the most voracious of the invertebrates.” This lead to the next question – did the feces of the fruit-eating camel crickets and ground beetles contain viable seeds?

Monotropastrum humile via wikimedia commons

After collecting a number of fecal pellets from the insects, Suetsugu determined that the seeds of all three species were “not robust enough to withstand mastication by the mandibles of the ground beetles.” On the other hand, the seeds passed through the camel crickets unscathed. A seed viability test confirmed that they were viable. Camel crickets were dispersing intact seeds of all three parasitic plants via their poop. The minuscule size of the seeds as well as their tough seed coat (compared to wind dispersed seeds of similar species) allowed for safe passage through the digestive system of this common ground insect.

In a later study, Suetsugu observed another mycoheterotrophic orchid, Yoania japonica, and also found camel crickets to be a common consumer of its fleshy, indehiscent fruits. Viable seeds were again found in the insect’s frass and were observed germinating in their natural habitat. Seutsugu noted that all of the fruits in his studies consumed by camel crickets are white or translucent, easily accessible to ground dwelling insects, and give off a fermented scent to which insects like camel crickets are known to be attracted. Camel crickets also spend their time foraging in areas suitable for the growth of these plants. All of this suggests co-evolutionary adaptations that have led to camel cricket-mediated seed dispersal.

Yoania japonica via wikimedia commons

Insect endozoochory may be an uncommon phenomenon, but perhaps it’s not as rare as we once presumed. As mentioned above, an instance of endozoochory by a beetle has been reported, as has one by a species of cockroach. Certainly the most well known example involves the wetas of New Zealand, which are large, flightless insects in the same order as grasshoppers and crickets and sometimes referred to as “invertebrate mice.” New Zealand lacks native ground-dwelling mammals, and wetas appear to have taken on the seed dispersal role that such mammals often play.

Where seeds are small enough and seed coats tough enough, insects have the potential to be agents of seed dispersal via ingestion. Further investigation will reveal additional instances where this is the case. Of course, effective seed dispersal means seeds must ultimately find themselves in locations suitable for germination in numbers that maintain healthy populations, which for the dust seeds of parasitic plants is quite specific since they require a host organism to root into. Thus, effective seed dispersal in these scenarios is also worth a more detailed look.

Further Reading:

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For more stories of seed dispersal check out the first issue of my new zine, Dispersal Stories.

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Selections from the Boise Biophilia Archives

For a little over a year now, I’ve been doing a tiny radio show with a friend of mine named Casey O’leary. The show is called Boise Biophilia and airs weekly on Radio Boise. On the show we each take about a minute to talk about something biology or ecology related that listeners in our local area can relate to. Our goal is to encourage listeners to get outside and explore the natural world. It’s fascinating after all! After the shows air, I post them on our website and Soundcloud page for all to hear.

We are not professional broadcasters by any means. Heck, I’m not a huge fan of talking in general, much less when a microphone is involved and a recording is being made. But Casey and I both love spreading the word about nerdy nature topics, and Casey’s enthusiasm for the project helps keep me involved. We’ve recorded nearly 70 episodes so far and are thrilled to know that they are out there in the world for people to experience. What follows is a sampling of some of the episodes we have recorded over the last 16 months. Some of our topics and comments are inside baseball for people living in the Treasure Valley, but there’s plenty there for outsiders to enjoy as well.

Something you will surely note upon your first listen is the scattering of interesting sound effects and off the wall edits in each of the episodes. Those come thanks to Speedy of Radio Boise who helps us edit our show. Without Speedy, the show wouldn’t be nearly as fun to listen to, so we are grateful for the work he does.

Boise Biophilia logo designed by Sierra Laverty

In this episode, Casey and I explore the world of leaf litter. Where do all the leaves go after they fall? Who are the players involved in decomposition, and what are they up to out there?

 

In this episode, Casey gets into our region’s complicated system of water rights, while I dive into something equally complex and intense – life inside of a sagebrush gall.

 

In this episode, I talk about dead bees and other insects trapped and dangling from milkweed flowers, and Casey discusses goatheads (a.k.a. puncture vine or Tribulus terrestris) in honor of Boise’s nascent summer celebration, Goathead Fest.

 

As much as I love plants, I have to admit that some of our best episodes are insect themed. Their lives are so dramatic, and this episode illustrates that.

 

The insect drama continues in this episode in which I describe how ant lions capture and consume their prey. Since we recorded this around Halloween, Casey offers a particularly spooky bit about garlic.

 

If you follow Awkward Botany, you know that one of my favorite topics is weeds. In this episode, I cover tumbleweeds, an iconic western weed that has been known to do some real damage. Casey introduces us to Canada geese, which are similar to weeds in their, at times, overabundance and ability to spawn strong opinions in the people they share space with.

 

In this episode, I explain the phenomenon of marcescence, and Casey gives some great advice about growing onions from seed.

 

And finally, in the spring you can’t get by without talking about bulbs at some point. This episode is an introduction to geophytes. Casey breaks down the basics, while I list some specific geophytes native to our Boise Foothills.

 

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Dung Moss (Revisited)

This is a revised version of a post that was originally published on January 14th, 2015. It includes excerpts from a chapter entitled, “Portrait of Splachnum,” in the book, Gathering Moss, by Robin Wall Kimmerer.

Certain plants, like corpse flowers and carrion flowers, emit foul odors when they bloom. The scent is akin to the smell of rotting flesh, hence their common names. The purpose of this repugnant act is to attract a specific group of pollinators: flies, carrion beetles, and other insects that are attracted to gross things. Though this particular strategy is rare, these aren’t the only plants that employ stinky smells to recruit such insects to aid in reproduction and dissemination. Consider dung mosses.

No moss is more fastidious in its choice of habitats than Splachnum. Absent from the usual mossy haunts, Splachnum is found only in bogs. Not among the commoners like Sphagnum that build the peaty hummocks, not along the margins of the blackwater pools. Splachnum ampullaceum occurs in one, and only one, place in the bog. On deer droppings. On white-tailed deer droppings. On white-tailed deer droppings which have lain on the peat for four weeks. In July.

At least three genera (Splachnum, Tetraplodon, and Tayloria) in the family Splachnaceae include species that go by the common name, dung moss. All Splachnum and Tetraplodon species and many species in the genus Tayloria are entomophilous. Entomophily is a pollination strategy in which pollen or spores are distributed by insects. Compare this to anemophily, or wind pollination, which is the common way that moss spores are distributed. In fact, dung mosses are the only mosses known to exhibit entomophily.

Dung Moss (photo credit: wikimedia commons)

Dung Moss (photo credit: wikimedia commons)

Before we go too much further, it’s important to understand how mosses differ from other plants. Mosses are in a group of non-vascular and non-flowering plants called bryophytes. Vascular tissues are the means by which water and nutrients are transported to and from plant parts. Lacking vascular tissues, water and nutrients are simply absorbed through the leaves and stems of mosses, which is why mosses are typically petite and prefer moist environments. Mosses also lack true roots and instead have rhizoids – threadlike structures that anchor the plants to their substrate of choice (such as dung).

Another major distinction between bryophytes and other plants is that bryophytes spend most of their life cycle as a haploid gametophyte rather than a diploid sporophyte. In most plants, the haploid gametophytes are the sperm (pollen) and egg cells; the sporophyte is everything else. In mosses, the familiar green, leafy structure is actually the gametophyte. The gametophyte houses sperm and egg cells, and when the egg is fertilized by sperm it forms a zygote that develops into the sporophyte structure which extends above the leafy gametophyte. A capsule at the top of the sporophyte contains spores which are eventually released and, upon finding themselves on a suitable substrate in a hospitable environment, germinate to produce new plants. The spore then is comparable to a seed in vascular, seed-bearing plants.

photo credit: wikimedia commons

photo credit: wikimedia commons

As stated earlier, the spores of most mosses are distributed by wind. Dung mosses, on the other hand, employ flies in the distribution of their spores. They attract the flies by emitting scents that only flies can love from an area on the capsule of the sporophyte called the apophysis. This area is often enlarged and brightly colored in yellow, magenta, or red, giving it a flower-like appearance which acts as a visual attractant. The smells emitted vary depending on the type of substrate a particular species of dung moss inhabits. Some dung mosses grow on the dung of herbivores and others on the dung of carnivores. Some even prefer the dung of a particular group of animals; for example, a population of Tetraplodon fuegiensis was found to be restricted to the feces and remains of foxes. However, dung is not the only material that dung mosses call home. Certain species grow on rotting flesh, skeletal remains, or antlers.

Splachnum ampullaceum inhabits the droppings of white-tailed deer. Had a wolf or coyote followed the scent of the deer into the bog, its droppings would been colonized by S. luteum. The chemistry of carnivore dung is sufficiently distinct from that of herbivores to support a different species. … Moose droppings have their own loyal follower. The family to which Splachnum belongs includes several other mosses with an affinity for animal nitrogen. Tetraplodon and Tayloria can be found on humus, but primarily inhabit animal remains such as bones and owl pellets. I once found an elk skull lying beneath a stand of pines, with the jawbone tufted with Tetraplodon.

Yellow Moosedung Moss (Splachnum luteum) has one of the largest and showiest sporophytes. (photo credit: www.eol.org)

Yellow moosedung moss (Splachnum luteum) has one of the largest and showiest sporophytes. (photo credit: www.eol.org)

The set of circumstances that converge to bring Splachnum into the world is highly improbable. Ripening cranberries draw the doe to the bog. She stands and grazes with ears alert, flirting with the risk of coyotes. Minutes after she has paused, the droppings continue to steam. … The droppings send out an invitation written in wafting molecules of ammonia and butyric acid. Beetles and bees are oblivious to this signal, and go on about their work. But all over the bog, flies give up their meandering flights and antennae quiver in recognition. Flies cluster on the fresh droppings and lap up the salty fluids that are beginning to crystallize on the surface of the pellets. Gravid females probe the dung and insert glistening white eggs down into the warmth. Their bristles leave behind traces from their earlier foraging trips among the day’s dung, delivering spores of Splachnum on their footprints.

The spores of dung mosses are small and sticky. When a fly visits these plants, the spores adhere to its body in clumps. The fly then moves on to its substrate of choice to lay its eggs, and the spores are deposited where they can germinate and grow into new moss plants. Flies that visit dung mosses receive nothing in return for doing so, but instead are simply “tricked” into disseminating the propagules. The story is similar with corpse flowers and carrion flowers; flies are drawn in by the smells and recruited to transmit pollen while receiving no nectar reward for their work.

There are 73 species in the Splachnaceae family, and nearly half of these species are dung mosses. Most are found in temperate habitats in both the northern and southern hemispheres, with a few species occurring in the mountains of subtropical regions. They can be found in both wet and relatively dry habitats. Dung mosses are generally fast growing but short lived, with some lasting only about 2 years. It isn’t entirely clear how and why mosses in this family evolved to become entomophilous, but one major benefit of being this way is that their spores are reliably deposited on suitable habitat.

Since Splachnum can grow only on droppings, and nowhere else, the wind cannot be trusted with dispersal. Escape of the spores is successful only if they have both a means of travel and a reserved ticket for a particular destination. In the monotonous green of the bog, flies are attracted to the cotton candy colors of Splachnum, mistaking them for flowers. Rooting about in the moss for non-existent nectar the flies become coated with the sticky spores. When the scent of fresh deer droppings arrives on the breeze, the flies seek it out and leave Splachnum-coated footprints in the steaming dung.

Sporophytes of Splachnum vasculosum (photo credit: www.eol.org)

Sporophytes of Splachnum vasculosum (photo credit: www.eol.org)

References

Koponen, A. 2009. Entomophily in the Splachnaceae. Botanical Journal of the Linnean Society 104: 115-127.

Marino, P., R. Raguso, and B. Goffinet. 2009. The ecology and evolution of fly dispersed dung mosses (Family Splachnaceae): Manipulating insect behavior through odour and visual cues. Symbiosis 47: 61-76.

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Grasshoppers – More Friend Than Foe?

Major outbreaks of grasshoppers can be devastating. A plague of locusts of biblical proportions can decimate crop fields and rangelands in short order. Clouds of grasshoppers moving in and devouring every plant in sight makes it easy to see why these insects are often seen as pests. Even small groups of them can do significant damage to a garden or farm. Yet, grasshoppers and their relatives have great ecological value and are important parts of healthy ecosystems. Love them or hate them, they are an essential piece of a bigger picture.

Grasshoppers are in the order Orthoptera, an order that includes katydids, crickets, wetas, and a few other familiar and not so familiar insects. Worldwide, there are more than 27,000 species of orthopterans. These insects mostly feed on plants; many are omnivorous while others are exclusively herbivorous. They are most commonly found in open, sunny, dry habitats like pastures, meadows, disturbed sites, open woods, prairies, and crop fields. Most insects in this order are fairly large, making them easy to identify; yet they don’t seem to receive the same level of human attention that charismatic insects like bees and butterflies do. In Field Guide to Grasshoppers, Katydids, and Crickets of the United States, the authors defend this diverse group of arthropods: “Grasshoppers often are thought of as modest-looking brown or green insects, but many species in this family are brightly colored, and some of the most dull-colored species rival butterflies in beauty when they spread their wings in flight.”

photo credit: wikimedia commons

photo credit: wikimedia commons

The voracious appetite of grasshoppers and their preference for plants can influence ecosystems in many ways. Certain plants may be favored over others, which affects the diversity and distribution of plant communities. Grasses are a particular favorite, despite being high in hard to digest compounds like lignin, cellulose, and silica. As grasshoppers consume vegetation – up to their body weight per day – digested materials return to the soil where soil dwelling organisms continue to break them down. In this way, grasshoppers and their relatives are major contributors to nutrient cycling. Returning nutrients to the soil results in increased nutrient availability for future plant growth. In fact, one grassland study found that despite short-term losses via grasshopper herbivory, plant growth was enhanced in the long-term due in part to accelerated nutrient cycling.

Because grasshoppers are such prolific consumers, their robust bodies are loaded with nutritious proteins and fats, making them a preferred food source for higher animals. Reptiles, raccoons, skunks, foxes, mice, and numerous species of birds regularly consume grasshoppers and related species. While many adult birds feed mostly on seeds and fruits, they seek out insects and worms to feed their young. Nutrient-packed grasshoppers are an excellent food source for developing birds. Humans in many parts of the world also find grasshoppers and crickets to be a tasty part of their diet.

Grasshoppers provide food for other invertebrates as well. The aforementioned field guide refers to the fate of grasshoppers and certain species of blister beetles as being “intimately linked,” because the larvae of these blister beetles feed exclusively on grasshopper eggs. Several species of flies and other insects, as well as spiders, also feed on grasshoppers and other orthopterans.

grasshopper on blade of grass

In short, grasshoppers play prominent roles in plant community composition, soil nutrient cycling, and the food chain. When grasshopper populations reach plague proportions, their impact is felt in other ways. From a human perspective, the damage is largely economic. However, their ability to thoroughly remove vegetation across large areas can be environmentally devastating as well, particularly when it comes to soil erosion and storm water runoff. The USDA’s Agricultural Research Service considers grasshoppers “among the most economically important pests” and cites research estimating that they are responsible for destroying as much as 23% of available range forage in the western United States annually. A paper published in the journal, Psyche, references a period between 2003-2005 in Africa where locusts were responsible for farmers losing as much as 80 to 100% of their crops.

This level of devastation is relatively rare. In Garden Insects of North America, Whitney Cranshaw states that of the more than 550 species of grasshoppers that occur in North America, “only a small number regularly damage gardens…almost all of these are in the genus Melanoplus.” Like most large, diverse groups of organisms, many grasshopper species are abundant and thriving while others are rare and threatened. Human activity has benefited certain species of grasshoppers while jeopardizing others. In general, grasshopper populations vary wildly from year to year depending on a slew of environmental factors.

Differential grasshopper (Melanoplus differentialis) - one of the four grasshoppers that Whitney Cranshaw lists as "particularly injurious" in his book Garden Insects of North America. (photo credit: www.eol.org)

Differential grasshopper (Melanoplus differentialis) – one of the four grasshoppers that Whitney Cranshaw lists as “particularly injurious” in his book Garden Insects of North America. (photo credit: www.eol.org)

A plague or outbreak of grasshoppers is a poorly understood phenomenon. It seems there are too many factors at play to pin such an occasion on any one thing. Warm, sunny, dry weather seems to favor grasshopper growth and reproduction, so drought conditions over a period of years can result in a dramatic increase in grasshopper populations. But drought can also limit plant growth, reducing the grasshoppers’ food supply. Natural enemies – which grasshoppers have many – also come into play. It seems that just the right conditions have to be met for an outbreak to occur – a seemingly unlikely scenario, but one that occurs frequently enough to cause concern.

Grasshoppers and fellow orthopterans are fascinating insects, and their place in the world is worth further consideration. For an example of just how compelling such insects can be, here is a story about crickets from Doug Tallamy’s book, Bringing Nature Home:

“Male tree crickets in the genus Oecanthus attempt to lure females to them by making chirping songs with their wings. The loudest male attracts the most females, so males often cheat a bit by positioning themselves within a cup-shaped leaf that amplifies the song beyond what the male can make without acoustical help. Each male chews a hole in the center of his cupped leaf that is just large enough to accommodate his raised wings during chirping. This ensures that the sound projects directly from the center of the parabolic leaf for maximum amplification.

Related Awkward Botany Posts:

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The Making of a Kill Jar

I often hear stories from plant lovers about their initial nonchalance concerning plants. The common refrain seems to be that they were fascinated by wildlife and largely ignored plant life until they came to the realization that plants were integral in the lives of animals and play a major role in shaping the environments that support all life. Such an epiphany spawns an insatiable obsession with botany, at least for some people.

I seem to be on the opposite trajectory. It’s not like I have ever really been disinterested in animals; I’ve just been significantly more interested in plants and haven’t bothered to learn much about the animal kingdom (with the exception of entomology). My growing fascination with pollination biology (see last year’s Year of Pollination series) isn’t much of a stretch because insects have always appealed to me, and their intimate interactions with plants are hard to ignore. Ultimately, it is my interest in urban ecology and wildlife friendly gardening that is driving me to learn more about animals.

I started this year off by finally reading Doug Tallamy’s popular book, Bringing Nature Home. Tallamy wrote a lot about birds in his book, which got me thinking more about them. I then discovered Welcome to Subirdia, a book by John Marzluff that explores the diversity of birds that live among us in our urban environments. I then found myself paying more attention to birds. Many bird species rely on insects for food at some point in their lives. Plants regularly interact with insects both in defending themselves against herbivory and in attracting insects to assist in pollination. It’s all connected, and it seems I wouldn’t be much of a botanist then if I didn’t also learn about all of the players involved in these complex interactions.

So, now I’m a birdwatcher and an insect collector. Or at least I’m learning to be. Insects are hard to learn much about without capturing them. They often move quickly, making them hard to identify, or they go completely unnoticed because they are tiny and so well hidden or camouflaged. With the help of a net and a kill jar, you can get a closer look. This not only allows you to determine the species of insects that surround you, but it can also help give you an idea of their relative abundances, their life cycles, where they live and what they feed on, etc.

insect net 2_bw

As the name implies, if you’re using a kill jar, your actions will result in the death of insects. Some people will be more pleased about this than others. If killing insects bothers you, don’t worry, insect populations are typically abundant enough that a few individuals sacrificed for science will not hurt the population in a serious way.

Kill jars can be purchased or they can be made very simply with a few easy to find materials. Start with a glass jar with a metal lid. Mix up a small amount of plaster of paris. Pour the wet plaster in the jar, filling it to about one inch. Allow the plaster to dry completely. This process can be sped up by placing the jar in an oven set on warm. When the plaster is dry, “charge” the jar by soaking the plaster with either ethyl acetate, nail polish remover, or rubbing alcohol. I use nail polish remover because it is cheap and easily accessible. It doesn’t work as quickly as pure ethyl acetate, but it is less toxic. Place a paper towel or something soft and dry in the jar. This keeps the insects from getting beaten up too much as they thrash about. Once the insect is dead, it can be easily observed with a hand lens or a dissecting microscope. It can also be pinned, labeled, and added to a collection.

There are several resources online that describe the process of collecting and preserving insects, including instructions for making an inexpensive kill jar, which is why I am keeping this brief and will instead refer you to a couple of such sites. Like this one from Purdue University’s extension program. It’s directed toward youth, but it includes great information for beginners of any age. This post by Dragonfly Woman is a great tutorial for making a kill jar, and there are several other posts on her blog that are very informative for insect collectors of all experience levels.

I guess you could consider this part of my journey of becoming a naturalist. Perhaps you are on a similar journey. If so, share your thoughts and experiences in the comment section below.

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Book Review: Bringing Nature Home

Since Bringing Nature Home by Douglas Tallamy was first published in 2007, it has quickly become somewhat of a “classic” to proponents of native plant gardening. As such a proponent, I figured I ought to put in my two cents. Full disclosure: this is less of a review and more of an outright endorsement. I’m fawning, really, and I’m not ashamed to admit it.

9780881929928l

The subtitle pretty much sums it up: “How You Can Sustain Wildlife with Native Plants.” Ninety three pages into the book, Tallamy elaborates further: “By favoring native plants over aliens in the suburban landscape, gardeners can do much to sustain the biodiversity that has been one of this country’s richest assets.” And one of every country’s richest assets, as far as I’m concerned. “But isn’t that why we have nature preserves?” one might ask. “We can no longer rely on natural areas alone to provide food and shelter for biodiversity,” Tallamy asserts in the Q & A portion of his book. Humans have altered every landscape – urban, suburban, rural, and beyond – leaving species of all kinds threatened everywhere. This means that efforts to protect biodiversity must occur everywhere. This is where the You comes in. Each one of us can play a part, no matter how small. In closing, Tallamy claims, “We can each make a difference almost immediately by planting a native nearby.”

A plant is considered native to an area if it shares a historical evolutionary relationship with the other organisms in that area. This evolutionary relationship is important because the interactions among organisms that developed over thousands, even millions, of years are what define a natural community. Thus, as Tallamy argues, “a plant can only function as a true ‘native’ while it is interacting with the community that historically helped shape it.” A garden designed to benefit wildlife and preserve biodiversity is most effective when it includes a high percentage of native plants because other species native to the area are already adapted to using them.

Plants (and algae) are at the base of every food chain – the first trophic level – because they produce their own food using the sun’s energy. Organisms that are primarily herbivores are at the second trophic level, organisms that primarily consume herbivores are at the third trophic level, and so on. As plants have evolved they have developed numerous defenses to keep from being eaten. Herbivores that evolved along with those plants have evolved the ability to overcome those defenses. This is important because if herbivores can’t eat the plants then they can’t survive, and if they don’t survive then there will be little food for organisms at higher trophic levels.

The most important herbivores are insects simply because they are so abundant and diverse and, thus, are a major food source for species at higher trophic levels. The problem is that, as Tallamy learned, “most insect herbivores can only eat plants with which they share an evolutionary history.” Insects are specialized as to which plants they can eat because they have adapted ways to overcome the defenses that said plants have developed to keep things from eating them. Healthy, abundant, and diverse insect populations support biodiversity at higher trophic levels, but such insect populations won’t exist without a diverse community of native plants with which the insects share an evolutionary history.

That is essentially the thesis of Tallamy’s book. In a chapter entitled “Why Can’t Insects Eat Alien Plants?” Tallamy expounds on the specialized relationships between plants and insects that have developed over millennia. Plants introduced from other areas have not formed such relationships and are thus used to a much lesser degree than their native counterparts. Research concerning this topic was scarce at the time this book was published, but among other studies, Tallamy cites preliminary data from a study he carried out on his property. The study compared the insect herbivore biomass and diversity found on four common native plants vs. five common invasive plants. The native plants produced 4 times more herbivore biomass and supported 3.2 times as many herbivore species compared to the invasive plants. He also determined that the insects using the alien plants were generalists, and when he eliminated specialists from the study he still found that natives supported twice as much generalist biomass.

Apart from native plants and insects, Tallamy frames much of his argument around birds. Birds have been greatly impacted by humans. Their populations are shrinking at an alarming rate, and many species are threatened with extinction. Tallamy asserts, “We know most about the effects of habitat loss from studies of birds.” We have destroyed their homes and taken away their food and “filled their world with dangerous obstacles.” Efforts to improve habitat for birds will simultaneously improve habitat for other organisms. Most bird species rely on insects during reproduction in order to feed themselves and their young. Reducing insect populations by filling our landscapes largely with alien plant species threatens the survival of many bird species.

In the chapters “What Should I Plant?” and “What Does Bird Food Look Like?,” Tallamy first profiles 20 groups of native trees and shrubs that excel at supporting populations of native arthropods and then describes a whole host of arthropods and arthropod predators that birds love to eat. Tallamy’s fascinating descriptions of the insects, their life cycles, and their behaviors alone make this book worth reading. Other chapters that are well worth a look are “Who Cares about Biodiversity?” in which Tallamy explains why biodiversity is so essential for life on Earth, and “The Cost of Using Alien Ornamentals” in which Tallamy outlines a number of ways that our obsession with exotic plants has caused problems for us and for natural areas.

Pupa of ladybird beetle on white oak leaf (photo credit: wikimedia commons)

Pupa of a ladybird beetle on a white oak leaf. “The value of oaks for supporting both vertebrate and invertebrate wildlife cannot be overstated.” – Doug Tallamy (photo credit: wikimedia commons)

Convincing people to switch to using native plants isn’t always easy, especially if your argument involves providing habitat for larger and more diverse populations of insects. For those who are not fans of insects, Tallamy explains that “a mere 1%” of the 4 million insect species on Earth “interact with humans in negative ways.” The majority are not pests. It is also important to understand that even humans “need healthy insect populations to ensure our own survival.” Tallamy also offers some suggestions on how to design and manage an appealing garden using native plants. A more recent book Tallamy co-authored with fellow native plant gardening advocate Rick Darke called The Living Landscape expands on this theme, although neither book claims to be a how to guide.

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Year of Pollination: Figs and Fig Wasps

This post originally appeared on Awkward Botany in November 2013. I’m reposting an updated version for the Year of Pollination series because it describes a very unique and incredibly interesting interaction between plant and pollinator. 

Ficus is a genus of plants in the family Moraceae that consists of trees, shrubs, and vines. Plants in this genus are commonly referred to as figs, and there are nearly 850 described species of them. The majority of fig species are found in tropical regions, however several occur in temperate regions as well. The domesticated fig (Ficus carica), also known as common fig, is widely cultivated throughout the world for its fruit.

common fig

Common Fig (Ficus carica) – photo credit: wikimedia commons

The fruit of figs, also called a fig, is considered a multiple fruit because it is formed from a cluster of flowers. A small fruit develops from each flower in the cluster, but they all grow together to form what appears to be a single fruit. The story becomes bizarre when you consider the location of the fig flowers. They are contained inside a structure called a syconium, which is essentially a modified fleshy stem. The syconium looks like an immature fig. Because they are completely enclosed inside syconia, the flowers are not visible from the outside, yet they must be pollinated in order to produce seeds and mature fruits.

This is where the fig wasps come in. “Fig wasp” is a term that refers to all species of chalcid wasps that breed exclusively inside of figs. Fig wasps are in the order Hymenoptera (superfamily Chalcidoidea) and represent at least five families of insects. Figs and fig wasps have coevolved over tens of millions of years, meaning that each species of fig could potentially have a specific species of fig wasp with which it has developed a mutualistic relationship. However, pollinator host sharing and host switching occurs frequently.

Fig wasps are tiny, mere millimeters in length, so they are not the same sort of wasps that you’ll find buzzing around you during your summer picnic. Fig wasps have to be small though, because in order to pollinate fig flowers they must find their way into a fig. Fortunately, there is a small opening at the base of the fig called an ostiole that has been adapted just for them.

What follows is a very basic description of the interaction between fig and fig wasp; due to the incredible diversity of figs and fig wasps, the specifics of the interactions are equally diverse.

First, a female wasp carrying the pollen of a fig from which she has recently emerged discovers a syconium that is ready to be pollinated. She finds the ostiole and begins to enter. She is tiny, but so is the opening, and so her wings, antennae, and/or legs can be ripped off in the process. No worries though, since she won’t be needing them anymore. Inside the syconium, she begins to lay her eggs inside the flowers. In doing so, the pollen she is carrying is rubbed off onto the stigmas of the flowers. After all her eggs are laid, the female wasp dies. The fig wasp larvae develop inside galls in the ovaries of the fig flowers, and they emerge from the galls once they have matured into adults. The adult males mate with the females and then begin the arduous task of chewing through the wall of the fig in order to let the females out. After completing this task, they die. The females then leave the figs, bringing pollen with them, and search for a fig of their own to enter and lay eggs. And the cycle continues.

But there is so much more to the story. For example, there are non-pollinating fig wasps that breed inside of figs but do not assist in pollination – freeloaders essentially. The story also differs if the species is monoecious (male and female flowers on the same plant) compared to dioecious (male and female flowers on different plants). It’s too much to cover here, but figweb.org is a great resource for fig and fig wasp information. Also check out the PBS documentary, The Queen of Trees.