Friday, November 21, 2014

My Metallic Green Bees

My favorite bee, Augochlora,
on cone flower.
© Beatriz Moisset

I often marvel at the exquisitely colored bees that visit my flowers. My favorite ones have a metallic green sheen that makes me think of them as miniature robots. How do they get such an interesting hue? Many other insects, such as wasps, flies, butterflies and beetles, also dress up on shiny armors. Metallic colors range from blue to copper and even red, with green being perhaps the most common. I decided to learn more about these shimmering hues, so different from ordinary colorations.

Another view of my favorite bee, the pure golden-green bee (Augochlora pura)
© Beatriz Moisset
It turns out that biologists have a lot to learn about this subject. The physics is quite complicated and I will not attempt to give more than the simplest explanation here. Most colors we see in nature are produced by pigments. The shiny and iridescent effects we see on certain animals are caused, not by pigments, but by tiny structures in the cuticle (the skin) of insects and thus they are called structural colors. Those microscopic ridges or plates or cross ribs make the light rays bounce off, scattering them in ways that produce special effects. The term iridescence lumps together three different types of chromatic effects: metallic looks, spectral iridescence (rainbow effects) and opal-like effects. Peacock feathers and Morpho butterfly wings are fine examples of iridescence. Some metallic colors observed in insects show a certain degree of iridescence. They change from green to copper or red depending on the angle of the light rays.

Parasitic wasp, Perilampidae.
© Beatriz Moisset
Pigments tend to decay after death, so ordinary tints usually fade away. Museum collections of dead specimens may look rather boring. In contrast, structural colors remain vibrant for a long time because the miniature structures don't change as long as the cuticle is intact. They may even be present in fossils.

Green-bottle blowfly, Lucilia.
© Beatriz Moisset
Let us get back to metallic colors, what function do they serve? Why do so many different insects wear these shimmering hard-looking coats? Some biologists think that structural colors serve functions of camouflage, signaling or disguise. What do these words mean? Can we find examples of these functions?

"Camouflage" enables the insect to blend with its surroundings and escape notice by predators. Let us look at my shiny bee. It blends moderately well with the foliage on which it often rests despite the fact that it is not a perfect imitation. It turns out that, while plants make green pigment in abundance, insects have trouble producing such pigment. The best approximation to the appearance of leaves is a structural color.

"Signaling" refers to sending a sign or a coded message to others. It may be a warning to predators, such as: I am poisonous; you don't want to eat me. It may be a message to other males of the same species: I am stronger, I am brighter; you'd better give up. Or, it may be telling females: I am the best male around.

Dogbane beetle.
© Beatriz Moisset
Finally "disguise" is a little different from camouflage. It is an imitation or mimicry of something else. The purpose is to deceive the observer

I hope you enjoy this gallery of metallic insects. It includes bees, wasps, flies, beetles and a butterfly. You may recognize some of these beauties in your garden or notice other ones.

Augochloropsis, a relative of Augochlora. © Beatriz Moisset



Parasitic wasp, Torymus. © Beatriz Moisset
Cuckoo wasp. Chrisididae. © Beatriz Moisset
Longlegged fly, Dolichopodidae. © Beatriz Moisset
Syrphid fly, Copestylum. © Beatriz Moisset
Tiger beetle. Cicindelidae. © Beatriz Moisset
Buprestid beetle. © Beatriz Moisset
Mating dogbane beetles. © Beatriz Moisset
Red spotted purple butterfly. © Beatriz Moisset



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© Beatriz Moisset. 2014 

Tuesday, November 18, 2014

Crab spiders hiding in goldenrod

Crab spider (Mecaphesa) on goldenrod. © Beatriz Moisset
Crab spiders are good at hiding among the flowers. Even after I annoyed this one quite a bit, it still remained somewhat hidden.

The same spider coming out of hiding. © 2007 Beatriz Moisset
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© Beatriz Moisset. 2014

Monday, November 3, 2014

Sticky Pollen


Arrowwood (Viburnum dentatum) in bloom. © Beatriz Moisset
 Some kinds of pollen are stickier than others. I marvel at that of arrowwood, Viburnum dentatum. These flowers attract numerous insects. The pollen coating can be impressive. It is hard to identify some of the bees when their features are hidden by abundant white dust.

Can you tell which kind of bee? © Beatriz Moisset
Probably the same bee. Hard to tell. © Beatriz Moisset
A closeup of another bee. © Beatriz Moisset
And one more. Take a look at those anthers. © Beatriz Moisset
Flower longhorn beetle taking a break. © Beatriz Moisset
Even the lady beetle larva gets coated with pollen. © Beatriz Moisset

Monday, October 20, 2014

Blowflies are Pollinators Too

Mating Lucilia flies. © Beatriz Moisset

A bright metallic green insect lands on one of the flowers in your garden. It has large red eyes. Aside from the interesting colors, it looks like a plump house fly. You can't decide whether you like it or not. Its scientific name is Lucilia, its common one is greenbottle blowfly. It is unusual for a scientific name to be prettier than the common name. You dislike the common name even more when you find out its meaning. According to the Free Dictionary a blowfly is "any of several flies of the family Calliphoridae that deposit their eggs in carcasses or carrion or in open sores and wounds." Carrion? Open sores? Definitely not pretty.


Lucilia on common milkweed. © Beatriz Moisset

So, it is agreed, Lucilia is an ugly fly despite its startling colors. But, does it have some redeeming features? Fortunately, it does. Its habits are put to full advantage in forensics. By examining the Lucilia's maggots found in a corpse it is possible to determine the time of death. Another use is in medicine. This may cause you some revulsion, but it isn't as bad as it seems. Open wounds that don't heal and begin to accumulate dead tissue can be cleaned up by blowfly larvae. Let me clarify that only maggots raised in perfectly sterile conditions are used for this purpose. The larvae feed only on the dead cells and leave the healthy tissue untouched. This method is superior to that of the most expert scalpel held by a surgeon.


© Beatriz Moisset

But this is a blog about pollinators, so let us get into this subject. Blowflies, Lucilia in particular, are good pollinators of certain flowers. You see them frequently visiting a variety of blooms in your garden. They are more efficient than bees in pollinating onions and cabbages. I wonder why they show such preference for plants so notorious for their strong odor. Perhaps there is a connection between these plants' fragrance and that of smelly dead things fowever I haven't found any references so far. Most pollinators don't fair well in greenhouses. Lucilia, on the other hand, is easy to raise and to maintain in these conditions, so this is the preferred pollinator of the mentioned plants.

Two Lucilia flies pollinating Allium. © Beatriz Moisset

In summary, blowflies aren't that bad at all. In fact, they are so beneficial that we may begin to see their beauty. Let us welcome them in our gardens.
Lucilia on mountain mint. © Beatriz Moisset


List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Thursday, September 18, 2014

Sneezeweed or Helenium


Halictid male bee on Helenium. © Beatriz Moisset
It is September, the days are getting shorter, the weather cooler. Plants put up a display that rivals or even surpasses that of spring. Asters, goldenrods, coneflowers and a number of other similar flowers create a golden explosion in gardens and meadows. Pollinators seem busier than ever, taking advantage of this bounty. Insect flower visitors love yellow and flowers seem to know it. They dress up in colors that attract their favorite visitors in the hope that they carry pollen to other flowers of the same kind. Pollinators, in turn, know that abundant resources await them in the bright yellow flowers.

Fig. 1. Three Helenium blossoms of different ages. © Beatriz Moisset
Let us look at one of these flowers in closer detail. Helenium, also called sneezeweed, has the same structure as sunflowers and asters, a crown of petals and a center made of little knobby structures called florets. Each one of those knobs is an entire flower which produces pollen and seeds. Each one needs to be pollinated in order to produce a seed. The dead heads you see later in the fall are little packages of these nutritious mature seeds that bring joy to passing hungry birds.

Fig. 2. Several Helenium or sneezeweed flowers. © Beatriz Moisset
The florets do not mature all at once. They proceed in an organized fashion from the outer ring to the center, row by row; they open and expose the pollen-carrying anthers and the pistils ready to receive pollen. They also fill up with nectar. Only one row or two at a time are ready to welcome visitors and to be pollinated. Bees know that. Even syrphid flies know that. You can see them moving from floret to floret until they complete the circle. Then they fly to the next blossom. They know enough not to waste time on the unopened flowers or the ones past their prime.

Bumble bee collecting pollen and nectar from open florets. © Beatriz Moisset
 Take a look at figure 1. The sneezeweed blossom near the center is quite fresh; most florets are still closed; only one is almost ready for pollination. The one in the upper right is halfway through; there are still some rows of unopened florets to go. The one below it is approaching old age, almost all done. Now, you can look at Helenium flowers and determine their approximate age just by looking at them. What do you think about the flowers in figure 2?

Another bumble bee. © Beatriz Moisset
 Smart pollinators, not only know where the food is in each flower, but also know that they will continue to find supplies in the following days. Bumble bees are known to faithfully come back to their favorite flower patches.

Sunflowers and asters do the same. See the following examples:

Agapostemon female on sunflower. © Beatriz Moisset



Halictid bee on coneflower. © Beatriz Moisset


Syrphid fly, Toxomerus on daisy. © Beatriz Moisset
 
Skipper on sunflower. © Beatriz Moisset



List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014


Sunday, August 31, 2014

The "Unbeetle" Beetle


© 2007 Beatriz Moisset
The distinguishing feature of all beetles is their hard external shell or coat. They don't seem to have wings. At least none are visible. The delicate, film-like wings of wasps and flies seem absent. But most beetles do have wings and fly quite well. The front wings of most insects have been modified in beetles into a hard case, called elytra, that covers and protects the second pair of wings. Their membranous hind wings remain out of sight, folded like origami. When they are ready to take off, the hinged hard elytra moves out of the way and the unfolded large hind wings are ready to go.

The exception to this rule is a peculiar insect without a common name and with just as peculiar a scientific name, Ripiphorus. In the case of this unusual insect the elytra are reduced to two little nubbins incapable of covering anything. The hind wings are longer than the beetles body, thin and translucent like those of wasps or flies. For lack of cover there is no point in folding them, so they are in plain sight all the time. I wouldn’t expect you to realize that it as a beetle if you are not an entomologist. I remembered being perplexed, myself the first time I saw one of these. You would probably ask: "Is that a wasp, or could it be some kind of fly?"

Male Ripiphorus beetle © 2011 Ilona Loser
 Some Ripiphorus are entirely black, others deep red. The males can be distinguished from the females by their flamboyant, feather-like antennae. Now, let us get back to its name and what it means. It should be spelled Rhipiphorus. Too bad the original author made a mistake and the rules of nomenclature prevent us from changing the original name. In Greek, it means a fan carrier, in reference to the male's impressive antennae. So, let this be its common name.

Female laying eggs. © 2007 Beatriz Moisset
You are more likely to see the females because they live a little longer than the males. They diligently visit flowers, not just any flowers, but only the fresher ones, the ones that are just beginning to open. They have a clever reason for doing this. They lay their eggs inside the blossoms and leave them to fend for themselves.

The newborn is not a defenseless shapeless grub like most beetle larvae. Instead it is mobile, with sharp claws, and can recognize a bee when it sees one. When a pollinator arrives at the flower, a few days later, the larva jumps into action and climbs into it. When the bee arrives at the nest with her load pollen and nectar, the little hitchhiker dismounts, ready to perpetrate its deed. Soon, it proceeds to feed on the bee's growing larvae and it may also consume some of the supplies. This is how a Rhipiphorus beetle makes a living, at the expense of an innocent pollinator's babies. Thus, it is considered a parasitoid, a word derived from parasite, but with a slightly different meaning. A parasite, ordinarily, doesn't kill its victim or host. The parasitoid behaves like a parasite at first but ultimately kills its host.

I feel sorry for the poor pollinator, but realize that this is the way of nature. I accept the behavior of this fascinating beetle and marvel at its strange looks and singular life style.

© 2007 Beatriz Moisset


List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Sunday, August 17, 2014

The Mason Wasp and the Caterpillar


Mason wasp, Euodynerus hidalgo and caterpillar
© Beatriz Moisset. 2014
Recently I found a wasp on a sunflower wrestling a caterpillar almost as big as herself into submission. The caterpillar had made considerable damage to the flower head as shown on the pictures. Finally the hunter managed to grip its prey by the throat, if that is where caterpillars have a throat. Carefully tucking her prey under her body, she flew away, presumably to her nest to feed her brood with it.

Caterpillar held firmly behind the head
© Beatriz Moisset. 2014
I identified the hunter as one of the mason wasps, so called because they use clay to build nest partitions. It was a rather small wasp, mostly black with yellow markings on its body. The wings remained folded lengthwise. All members of the family Vespidae do this when not in flight. Now, I finally could decipher the mystery presented to me a year earlier in the same garden where I was doing my observations.

On that occasion, I noticed a mason wasp furiously searching a flower head, almost a carbon copy of the one in front of my eyes. It had the same kind of damage, but, at that point, I didn't know what or who had caused it. The mason wasp rummaged the entire center of the blossom, even burying half of her body in it with no apparent success. After observing these antics for a while I moved on without finding out what she was looking for. Now, I had the answer.

Another mason wasp found a year earlier
© Beatriz Moisset. 2014
 A mother mason wasp, like the one I was observing, builds her nest inside any available hole of the right size, slightly wider than her own body. It could be a hollow stem or some other cavity previously dug up by a beetle or other insect. Unlike their distant cousins, hornets and yellowjackets, they don't form large colonies. Each mother wasp minds her own business, builds a nest where it raises maybe a dozen babies and is not inclined to defend this small investment as ferociously as hornets tend to do. Thus, their presence can be easily tolerated in the garden.


Mason wasp tending her nest

Interestingly the so called mason bees have similar nesting habits. These bees are excellent pollinators of fruit trees and other plants, so gardeners prize their services. Some gardeners provide housing for them by hanging a bundle of hollow twigs or drilling a number of holes in a piece of wood. These bee houses and bee hotels have been growing in popularity in recent years. You can purchase them from several venues usually accompanied by an instructions booklet.

© Beatriz Moisset. 2014
Mason wasps use caterpillars to feed their babies. They keep their prey alive, so the food supply remains fresh as long as needed. They do so by paralyzing but not killing their victims with their stingers, a delicate operation. This is why my wasp was so busy getting the right hold of the caterpillar, firm but not too harsh.

Most adult wasps are often seen on flowers because they feed mostly on nectar. This particular species has another reason for visiting flowers. This is where it finds its prey. Some caterpillars, especially some inchworms and owlet moths, show a preference for sunflower heads. They hide in the very heart of the flower and proceed to eat the growing seeds causing a bit of destruction. It is nice to see that this hunting wasp prey on them preventing further damage.

If you love pollinators you may be raising mason bees. Perhaps you find some of the holes in your bee houses occupied by mason wasps. You may be tempted to destroy the "invaders." Please, don't! You probably didn't know that they help the pollinators by keeping down the populations of plant eating insects. We need biological controls as much as we need pollinators to maintain a healthy garden.

Additional readings
In Praise of Wasps
Urban Bee Gardens. Berkeley University
Nests for Native Bees. The Xerces Society
Bee houses. National Wildlife Federation. (How to build a bee house)

Sellers of bee houses
Knox Cellars.
Mason bee homes.


List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014