Thursday, November 1, 2012

Monarchs and their Enemies

Male monarch butterfly. © Beatriz Moisset

We are told that monarch butterflies are well protected against predators and indeed they are. Their caterpillars feed on milkweeds, rich on highly toxic substances known as cardenolides. Having developed resistance against these chemicals, the monarchs themselves are poisonous so predators avoid them. A young, inexperienced bird that takes a bite off of a caterpillar or a butterfly spits it out in disgust and may be sick afterwards. It learns its lesson after no more than one trial.

Are monarchs completely free from enemies, then? Not so, there are exceptions. A number of predators and parasites have also become tolerant or immune to the cardenolides. Thus, they can feed on monarchs with relative impunity. The list of predators includes birds, mice and insects. Monarchs can also become victims of certain pathogens.

Robin. © Beatriz Moisset
Brown thrashers, grackles, robins, cardinals, sparrows, scrub jays and pinyon jays are known to feed on monarchs. Some of these birds avoid the body parts with higher concentrations of cardenolides by eating only the abdomens or by eating this kind of food in moderation. When monarchs arrive in their wintering grounds in Mexico they are plump with stored fats that will keep them through the winter. A whole new set of predators is eagerly awaiting them. Mice feast mostly on dead and dying butterflies that have fallen to the ground. Several species of birds, especially black-backed orioles and black-headed grosbeaks take a heavy toll on the millions of wintering butterflies. A few months after their arrival in Mexico, the monarchs may have lost a fair amount of toxins, making them more appetizing. It is estimated that between 7 and 40% of them fall victims to predation in their roosting grounds.

Small milkweed bug. © Beatriz Moisset

Invertebrates may be worse than mice and birds at decimating the populations of monarchs. Eggs, caterpillars and pupae are all vulnerable. The small milkweed bug doesn't just eat milkweed. It becomes carnivorous in occasions and catches milkweed caterpillars.

Spined soldier bug. Podisus maculiventris. © Beatriz Moisset
The spined soldier bug is an indiscriminate predator of many species and is not averse to feeding on monarchs. It impales caterpillars larger than itself and feeds on the internal fluids. (View of a spined soldier bug feeding on a monarch caterpillar).

Polistes paper wasp. © Beatriz Moisset

Paper wasps, Polistes, sometimes attack monarch caterpillars or pupae to feed their young. Recent reports suggest that this form of predation is more common than originally thought. (View of several paper wasps collecting food from a monarch chrysalis).

Asian lady beetle or ladybug. © Beatriz Moisset

In addition to all these native predators, the introduced Asian lady beetle is becoming a serious enemy of monarch eggs and caterpillars.

Tachinid fly. © Beatriz Moisset

Several tachinid flies and parasitic wasps lay their eggs on the monarch caterpillars for their larvae to feed on. All these insect predators and parasites probably consume a substantial number of monarchs before they even reach maturity.

Parasitic wasp, Pteromalid. © Beatriz Moisset

You may feel sorry for the monarchs; but this is the way of nature. Everything is interconnected and monarchs are not the exception. Sad as it seems, these butterflies serve a purpose by being part of the food chain. They produce enough eggs to survive and prosper despite the attacks. They could go on for thousands of years as they have already done, feeding on milkweeds and providing food for other forms of wildlife. The biggest threat to them does not come from those that feed on them but from the changes we are introducing in the planet.

Another frequent enemy of monarch caterpillars is a predatory stink bug, Stiretrus anchorago (Anchor stink bug).

Further readings:
Parasites Affecting Monarchs. University of Georgia
Parasites and Natural Enemies. University of Minnesota
A Butterfly's Flashy Colors.

List of articles

© Beatriz Moisset. 2012

Tuesday, October 16, 2012

Ants, the Unlikely Pollinators

© Beatriz Moisset

Ants are seen visiting flowers with great frequency. People often ask me: Do ants pollinate? I answer with another question: What do you think? Are ants capable of pollinating flowers? Do they have what it takes to carry pollen from one flower to another, preferably of another plant?

Ants stealing nectar from the spur of a jewelweed. © Beatriz Moisset
Most pollinators can fly from plant to plant. Ants, lacking wings, don't go very far. Moreover, ants may be coated in some sort of antibiotics which may be detrimental to pollen. In some cases ants steal nectar from flowers, causing damage and reducing the likelihood of later pollinators' visits. Some plants resort to extrafloral nectaries, nectar-producing glands located in other plant parts, to keep the ants and other nectar robbers away from the valuable treasure reserved for legitimate pollinators.

Ants pollinating wood spurge. © Beatriz Moisset
Despite all these drawbacks, there are instances in which ants are pollinators. One case is that of spurge, or Euphorbia. This plant grows very low near the ground and tends to intertwine its runners with those of nearby plants. This increases the chances of ants going from the flowers of one plant to those of another without the need to fly. Perhaps the pollen of spurge is more resistant to the chemicals on an ant's body. So, ants pollinate spurge; although, there are also small bees that perform this job just as well.

A few other plants, also low-growing, are pollinated by ants. Finally, there are some interesting cases of orchids pollinated by ants in Australia in a highly specialized way. So, yes, ants join the ranks of pollinators. They may even be the pollinators of choice for some plants in harsh, dry climates.

Ant on Queen-Anne-lace. © Beatriz Moisset

List of articles

© Beatriz Moisset. 2012 

Monday, September 3, 2012

Cast of Characters

Every year flowers bloom in succession and, with them, a predictable cast of characters shows up routinely. Three plants, in particular, call your attention for the numerous repeat patrons to these restaurants and their nectar: common milkweed, mountain mint and goldenrod. Or you may regard the visitors as actors hired to play roles in these theaters. The truth is that every year the theaters have to hire the descendants of previous visitors. The original ones are long gone. Here are some of the representatives of the mountain mint crowd, each photo accompanied by a great-grandchild or great-great-grandchild repeating their roles:

Great golden digger wasp and grandchild (2004 and 2006)

Red banded hair streak butterfly and great- great- great-... well, let us say that at least six generations have elapsed between one and the other (2006 and 2012). It looks like both pictures were taken the same day.

Macrosiagon limbata wedge shaped beetle and his great-granddaughter (2004 and 2007)

Not a very nice fellow. It lays its eggs on the flowers and the little larvae hitches a ride from a passing bee. Then they feed on the bee's stored food and on the bee baby. The adults are so short lived that you don't see them visiting earlier or later blooming flowers.

The wasp and the butterfly also play in many other theaters through the seasons. The beetle, on the other hand, is most often seen on this plant.

Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012

Wednesday, May 30, 2012

Gardening for Honorary Butterflies (Mint Moths)

Not all moths fly at night and not all are drab. Some deserve the name of honorary butterflies. In fact sometimes they are mistaken for them. Sorry I tricked you by using the word butterflies in the title (not really); but I was afraid that most would ignore this article if they just saw the word moths. The fact is that there are ten times more species of moths than of butterflies; that they are very important components of ecosystems and worth welcoming in our gardens. Some are very beautiful and can give visual enjoyment to the gardener. To me, most if not all are beautiful each in its own way. But I know people who dislike, fear or hate moths in general. I hope that at least they take time to look and learn to love the pretty ones.

I will save some of the most striking ones, such as hummingbird, imperial and Luna moths for later. I will start with some that many people are unaware of and amazed when they first see them.

The crambid snout moths represent a family (Crambidae) with more than 850 species in North America. They get their common name from the appendage that sticks out on front of their heads. Some of them, the members of the genus Pyrausta feed on plants of the mint family, so I will be calling them mint moths, although they don't really have a common name. Most of them are brightly colored and are seen during the day.
Pyrausta orphisalis (Orange Mint Moth) on mountain mint
©Beatriz Moisset

The larvae of the orange mint moth (Pyrausta orphisalis) feed on a variety of mints and sometimes you cans see signs of their feeding, especially at the buds and newer leaves. But the damage is not known to reach serious proportions. It is good to remember that caterpillars are bird food. So it is a good idea to have a few well behaved caterpillars such as these ones to attract birds to the garden. It is also a pleasure to spot this very attractive moth resting on a plant of mint.

Pyrausta signatalis (Raspberry Pyrausta) on mint
©Beatriz Moisset

The raspberry mint pyrausta (Pyrausta signatalis) is also richly colored and earns its name because of the raspberry color of its wings. The larvae feed primarily on spotted beebalm (a member of the mint family), they also feed on a few related plants such as wild bergamot and scarlet beebalm.

Pyrausta tyralis
  © Bob in swamp Flickr
 Another member of this genus, even more striking in its coloration is the Coffee-loving pyrausta (Pyrausta tyralis). This one breaks the mold with its feeding habits, a peculiar feat. It gets its name because it likes wild coffee (Psychotria nervosa) found in Florida. It also feeds on some Asteraceae such as dahlia and bidens.

It is worth mentioning that there are many species of mint moths in Europe. Here is a gorgeous one: the golden mint moth (Pyrausta aurata).

Pyrausta aurata © Bramblejungle Flickr

In summary, if you want to attract these honorary butterflies to your garden plant a variety of mints including beebalm which by the way is also good at attracting hummingbird moths and hummingbirds.

Moth as Pollinators
List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012 

Tuesday, May 1, 2012

Pollinator Conservation Short Course

Snyder Farm

On April 27, I attended a short course on pollinator conservation at the Snyder Farm, an agricultural research station of Rutgers University, located in Pittstown, NJ. It was sponsored by Rutgers University, the Xerces Society for Invertebrate Conservation and the Natural Resources Conservation Service (NRCS). There were very informative sessions in the morning and a walk of the property in the afternoon ending with information on the current Farm Bill provisions for pollinator conservation.

We learned about recent research about the most common native pollinators of crops in New Jersey, several bumble bees and sweat bees among others. This is probably applicable to most of the Mid Atlantic region. We were informed about recent studies on the best native plants for pollinator gardens adjunct to farms. Among them some very familiar ones such as: cutleaf coneflower, some types of goldenrods, butterfly and swamp milkweeds, Joe pye weed and New England aster.
One of the best ecosystem-service providers, Bombus impatiens, on one of the best plants for pollinators, New England aster

There were presentations on how to protect pollinator habitats: bare spots in the ground, logs or old trees and plants with hollow twigs; all of them provide nesting places. Perhaps most important is the use of Integrated Pest Management, to reduce pesticides to the bare minimum and to use them only very early or very late in the day, when pollinators are less likely to be active. See: Attracting native Pollinators, Pollinator Friendly Planting Guide.
Canola fields

During the walk we visited the fields of rapeseed or canola, which are captivating with their incredibly bright yellow flowers at this time of the year. Sadly for us the wind was so strong, sharp and continuous that flower visitors were notoriously absent that day.  The pollinator garden was at an incipient stage. Its value will increase with time. We were shown how to do an assessment of native bee conservation practices; for instance, the presence of a windbreak, hedgerows between fields or along the edges of the property, presence of nest sites and natural vegetation within certain distances, etc. This assessment is used later on to evaluate any improvement.
Pollinator garden

What was completely disconcerting to me was the huge expanse of lawn near the farmhouse and between orchard fields. It would have been more acceptable if the lawn was heavily sprinkled by "grass companions", broad leaved weeds which can provide food for many sorts of pollinators. I didn't see any broad leaved plants worth mentioning. To make sure I was seeing right, I got on my hands and knees and only saw some solitary gill-of-the-ground and the occasional violet. I have seen many suburban lawns that are friendlier to pollinators without really trying.
A wasted opportunity, huge pollinator unfriendly lawn

 Perplexed, I asked Tim Dunne, the NRCS representative, about it. He agreed that such lawn was not exactly pollinator heaven. He has tried to change such practice without success. The farmer in charge of planting and maintenance emphatically refuses to have weeds which, according to him, would promptly invade the orchards. By looking at that lawn, I am sure that they are using herbicides, a practice that makes no sense at all when you are trying to create a pollinator habitat. The few square yards of pollinator garden look puny by comparison with the several acres of pollinator unfriendly lawn I saw that day.
Bluets, one of many lawn companions good for pollinators
Another good lawn companion, low growing aster

It is time that somebody comes up with good seed mixes for pollinator lawns. Sam Droege of the USGS said it very eloquently in 2009 in an e-mail to the Bee Monitoring group.
"What if someone would develop a bee lawn seed mix? 
Wouldn't that potentially have a higher impact on the number and kinds of bees in urban areas than the high effort, high cost, high maintenance (but, yes, very pretty) pollinator garden?"

These mixtures should include lawn companions beneficial to pollinators, non-invasive and reasonably easy to maintain. Meeting these requirements should be easier in a farm than in a suburban garden setting; foot traffic and looks are not important. The Xerces Society advocates the use of "ecolawns". It also was one of the sponsors of this workshop. So why aren't they doing more for pollinator lawns?
Another good pollinator for farm fields, Augochlora pura

Lawns for pollinators, grass companions
Lawn for pollinators. Part II
Lawn for pollinators. Part III

List of articles
Beginners Guide to Pollinators and Other Flower Visitors
© Beatriz Moisset. 2012

Wednesday, April 25, 2012

Moths as Pollinators

Moths evolved to deal with flowers. Their long, tube-like tongues are just right for sipping nectar from long-necked blossoms. Nectar is practically the only food of adult moths, thus a strong partnership with flowers developed. We are familiar with butterflies pollinating flowers, but easily forget about moths. Actually, butterflies are a specialized type of moths, or, more properly they are all Lepidoptera.

Then, it is important to learn more about the role of moths in pollination. Here are a few articles that deal with this subject.

Yellow-collared scape moth on turtlehead
Black-and-yellow lichen moth, a little known pollinator
Crambid snout moths
Gardening for Honorary Butterflies: Mint Moths
Hummingbird Moths. Where do they go in Winter?
Inch worms: more little known pollinators
Little known moth pollinators: seed casebearers and flower moths
Metalmark moths. More little known pollinators
Noctuids, another family of little known pollinators
Plume Moths. More Little Known Pollinators
Pollinators, the Night Shift
Yellow-collared scape moth
The Yucca Moth and the Yucca
Zygaenidae, more little known pollinators
Geometrid caterpillar, or inchworm (Eupithecia) on sunflower

Other Articles on Moths and other Lepidoptera:

Bugs in the Garden. Hornworm: Friend or Foe? Friend and Foe
Caterpillars are for the Birds
Food for wildlife
Gardening for Honorary Butterflies (Mint Moths)
Pollinators in Winter: Fritillaries

Hummingbird moth on Monarda
Hummingbird Moth
Hawk Moths
Ailanthus Web-worm Moth
Yellow-collared Scape Moth
Carnivorous Lepidoptera. In
Projectile Frassing. In Flickr
Pollinators in second shift: moths. Dave's Garden
Pollination by Nocturnal Lepidoptera and Effects of Light Pollution: a Review

List of articles 

© Beatriz Moisset. 2012

Saturday, March 31, 2012

The Yucca Moth and the Yucca

Yucca (Yucca glauca), the state flower of New Mexico, illustrates an intimate relationship between a specialized pollinator and its equally specialized flower. The plant and the insect co-evolved; that is, they developed in intimate connection with each other. This is called an obligate mutualism in which if one were to disappear, the other would follow the same path. Originally it was a relationship of exploitation, with the moth larvae feeding on the seeds of the yucca. But, eventually the plant devised methods to take advantage of the situation and as a consequence, the moth also evolved to ensure food for its babies and preservation of its food plant.

Yucca flowers open for a few days, attracting a variety of insects during day hours; but they produce more nectar and send their strong and sweet aroma at night. Flowers with these characteristics are usually pollinated by moths or other nocturnal pollinators.

The yucca adds a special embellishment to this arrangement; of all the insects that visit its flowers, the only ones that can accomplish pollination are the yucca moths (Tegeticula yuccasella and Parategeticula depending on the species of plant).

Yucca moths are small, white, not very noticeable. They spend a good part of their adult life inside the flowers of the yucca, meeting members of the opposite sex and mating. Once mating has taken place, the female, very purposely visits the male parts of the flowers (anthers) to collect pollen which she stores under her chin.

Later, she flies to another flower, inspects it carefully, and if no other female has deposited her eggs, she proceeds to do just that. She refrains from laying more than a small number of eggs. The larvae will feed on the seeds of the plant. She seems to know that if she gets carried away and lays too many eggs, the flower will abort rather than produce a seedless fruit. It would be a no win situation, both for the plant and the moth.

Then, just as purposely as before, she goes to the right place, at the top of the ovary (called stigma), and deposits some of her precious cargo of pollen from under her chin, ensuring, this way, that the seeds will grow and feed her babies. She repeats this operation in other flowers.

The larvae feed on some of the seeds and there are enough left for the plant to reproduce. When fully grown, the larvae drop to the ground, where it goes through the transformation called pupation and finally it emerges as an adult several months later to repeat the cycle.

Without this insignificant little moth, the landscapes of the west would look dramatically different in the absence of yucca.

© Cillas. Wikicommons
Read more:

Moths as Pollinators
List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012

Sunday, March 25, 2012

Plume Moths: More Little Known Pollinators

Himmelman's Plume Moth

The plume moths or Pterophoridae get their name because of their feathery wings. Their aspect is quite unusual for a moth. The wings are narrow and fringed by bristles. When resting they spread their wings looking like the letter T. Their wing span ranges from ½ to 2 ½ inches. Most have a pattern of broken colors, tan and white or brown and white. The legs also present bristles. The combination of these colors and their shape makes them look like a piece of dry grass. Probably this helps them to escape predators' notice. They are easily missed by this photographer although in plain view. You may have seen one resting on your window screen where they are easier to notice

There are about 150 species in North America; most are hard to tell apart. A very common one is the Himmelman's Plume Moth or Geina tenuidactylus.

They are seen at flowers frequently, so they may be pollinators; although I don't know of any studies about it. More is known of their role as pests of some ornamentals and as biological control to keep in check some introduced invasive plants

Himmelman's Plume Moth

Moths as Pollinators
List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012

Wednesday, March 21, 2012

Of Spring Beauties and Lesser Celandines

A few spring beauties surrounded by the invasive lesser celandine

Lesser celandine along the trail where native flowers used to be
Last year I was disheartened to find that the lesser celandine, that attractive but aggressive invader, had spread over the land that once belonged to spring beauties and trout lilies. I am sorry to say that it looks like the non-native continues to make inroads.

Pachysandra, upper right corner; snow drops, bottom; spring beauties, center; lesser celandine. There are also stems of another alien, multiflora rose

Lesser celandines, with the help of snow drops and pachysandra, all of them garden escapees, have taken over the forest floor along my favorite nature trail. Later on, garlic mustard will show up in all the same places, but now it is not in sight. Snow drops were in bloom the last couple of weeks and now they are past their prime. This is another delightful but aggressive invader which brings joy to the hearts of many with its early blooms. Spring beauties struggle to survive hemmed in by all these newcomers to the land. Trout lilies face the same predicament in these areas.

A patch of lesser celandine
This spring I want to see how our native spring beauties and their pollinators are faring among the many introduced plants. So a few days ago I sat on my little stool on front of a patch of lesser celandine. It was a warm and sunny day and insects were quite active, including some gnats that enjoyed attacking my ears and forehead. During my forty minutes of observation I saw a number of little dark insects approach the patch and inspect the blooms by briskly hovering above them. Only one landed on a flower and stayed long enough for me to recognize it as an Andrena bee, the kind that would be loading her leg baskets with pollen from spring beauties if there were any around. Soon it left without attempting to gather anything from the flower. Perhaps it was just using it as a perch to pause during an exhausting and frustrating search for its favorite food.

Another patch of lesser celandine, near a stream
I continued my observations two days later. For more than an hour I walked along the trail illustrated above. I kept my eyes open for flower visitors and made frequent stops. I found only a handful of spring beauties nearly smothered by the lesser celandines. Even that very low number managed to have a few visiting bees. On the other hand, the bright yellow blossoms of lesser celandine remained neglected by anybody other than a small gnat and a beetle.

Finally, I sat for half an hour on front of another patch of lesser celandine, as on the previous time and intently looked for flower visitors. Finally a honey bee showed up and methodically worked the flowers. Let us remember that both honey bees and lesser celandines are European imports. There were no native pollinators in sight.

I should be glad that the lesser celandines don't get pollinated; but I can't. The variety brought from Europe propagates primarily by small bulbs (bulbils) with no need for pollinators. It reproduces this way only too well. Its abundance and the growing scarcity of spring beauty flowers forces the Andrena bees to travel longer and longer distances to gather pollen for their young. As a result, they can raise fewer and fewer babies each year. Both the flower and its pollinator continue to lose ground to the invaders.
A spring beauty and its pollinator, a rarer sight each year

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012

Sunday, March 11, 2012

Zygaenidae, more little known pollinators

Harrisina americana (Grapeleaf Skeletonizer) on common milkweed

Another family of moths with a number of species that visit flowers is Zygaenidae. Many of them are day flying moths and, as usual, they are more colorful than night flying ones. Some are known to pollinate orchids. Their larvae feed on foliage, eating everything but the veins of leaves, so one common name for them is leaf-skeletonizers.
Acoloithus falsarius (Clemens' False Skeletonizer)

Two of them are frequently seen on milkweed flowers, the grapeleaf skeletonizer and Clemen's false skeletonizer. They are both dark blue or blue gray with a bright orange collar. The Clemen's moth is smaller than the grapeleaf skeletonizer. What is interesting about this imitative pattern is that it also mimics that of another common flower visitor, the yellow-collared scape moth. As mentioned before, the latter is toxic to predators and uses its colors to advertise its toxicity. The same thing is true of members of the Zygaenidae family. These, as well as some beetles, form part of a large mimicry complex, a fine example of Mullerian mimicry, in which they all benefit from this use of a similar warning pattern; predators need to learn their lesson only once, so more members of the guild escape attacks.
Cisseps fulvicollis (Yellow-collared Scape Moth). An unrelated moth member of the guild

Asclera ruficollis (Red-necked False Blister Beetle). A bettle member of the same mimicry guild

Another Zygaenidae that frequents flowers is the orange-patched smoky moth. Its wings are dark gray or black near the farther tip; the front half is orange. They too are members of another group of moths and also beetles with a pattern that warns predators. You can see some in a previous post: the black and yellow lichen moth and the end band net-wing lycid beetle.
Pyromorpha dimidiata (Orange-patched Smoky Moth)

Moths as Pollinators
List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012