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

Monday, July 28, 2014

Hairy-legged Fly, a Gardener's Friend

Female Trichopoda pennipes. © Beatriz Moisset
Unsung insect heroes of the native plant garden abound. Pest fighters such as lady beetles, praying mantises and lacewings are receiving growing attention. But pest fighting doesn't end with the three above mentioned. Wasps and flies of many sorts provide invaluable pest control services. Let us look at one of them, the hairy-legged fly (Trichopoda pennipes).

Male Trichopoda pennipes. © Beatriz Moisset
The abdomen of the colorful hairy-legged fly is bright red or orange on the male and with a black tip on the female. Both wear funny looking bell-bottoms on their third pair of legs. This flare is made of a tuft of hairs that gives these flies their name. Like all other flies, they have only one pair of wings. The back wings have been reduced to small balancers, called halteres, hard to see in most species. This fly is the exception. The halteres are relatively prominent and bright orange. If you have been struggling to identify flies by the number of wings and the presence of halteres, you want to start with this example.

They are often seen visiting flowers and drinking nectar. Thus they may perform some pollination. But their most important role in the garden is what they do to feed their young. They hunt a variety of insects on which they lay a single egg. When the baby or larva emerges from the egg, it drills into the hapless bug and proceeds to eat its insides.

Green stinkbug, Chinavia hilaris. © Beatriz Moisset
Two insidious pests are among its favorite hosts: the green stink bug and the squash bug. The green stink bug attacks a number of crops, including corn, cotton and soy bean. The squash bug feeds on squash and related vine crops.

Squash bugs, Anasa tristis on pumpkin. © Beatriz Moisset
The hairy-legged fly deserves more recognition than it gets. If you want to encourage it to visit your garden, reduce or eliminate pesticides and provide native flowering plants that bloom through the seasons so the adults find nourishment. If you are helping pollinators you are probably doing all this already.

Male Trichopoda pennipes. © Beatriz Moisset

Just the fly for your pumpkin patch

For more on pollinators and other flower visitors read the e-book:
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Tuesday, July 22, 2014

Flower Longhorn Beetles, the Elegant Crowd

Strangalia luteicornis on buttonbush
© Beatriz Moisset
 Most beetles we are familiar with are roundish or oval-shaped hard shelled insects. Think ladybugs or Japanese beetles. Others are a little longer and cigar-shaped. An entire group of beetles distinguishes itself for its elegant streamlined figure; these are the so called flower longhorns. The name refers to their love of flowers as a hangout and to their long antennae. No, they don't have real horns, just antennae like other insects. Sometimes these organs can be longer than their entire body.

Strangalia famelica, the hungry strangalia
© Beatriz Moisset
Flower longhorns are the fashion models of the beetle world. Their slender and highly stylized outline is reminiscent of that of wasps; although they would never be mistaken by such because they have the characteristic hard shell (elytra) of all beetles covering their membranous wings. In their elegance they would make a nice fashion parade. Some carry their slenderness to the extreme of appearing anorexic. In fact one of them was given the scientific name of famelica, which means starved one in Latin. By contrast, the banded longhorn (Typocerus) and Brachyleptura appear almost obese, although they are still rather slender when compared to most beetles.

Brachyleptura rubrica covered with pollen
© Beatriz Moisset

The banded longhorn, Typocerus velutinus on milkweed
© Beatriz Moisset
Flower longhorns love flat open blossoms of the umbrella type, such as the members of the carrot family. They also like flowers of the rose and aster family as well as wild hydrangea. They feed on their pollen. Sometimes you find several different types amiably mingling together on these flowers. They are regarded as lesser pollinators of such plants. It is not surprising, when you see some of them coated with pollen.

A couple of Metacmaeops vittata on wild hydrangea
© Beatriz Moisset
Their larvae don't have such wholesome habits. They are wood borers, meaning that they feed on wood. However none has been reported as a serious pest of trees. Perhaps trees have enough defenses against them or there are enough enemies to keep their numbers from getting out of control.

Analeptura lineola on wild hydrangea, with pollen on its back
© Beatriz Moisse
Flower longhorn beetles are a beautiful addition to the biodiversity of forests, well integrated with the remaining members of the community.

For more on pollinators and other flower visitors read the e-book:
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Sunday, July 6, 2014

The Great Impersonators, flower flies

Eristalis tenax, the drone fly, a honey bee mimic
© Beatriz Moisset

Why would one insect want to look like another? There must be some advantage in doing so. When it comes to flower flies the answer becomes apparent after a little observation.

These flies are found visiting flowers rather than garbage or dead meat like some of the flies you are most familiar with. They are rather pretty, with patterns of brown and yellow or black and yellow which easily remind you of bees. I have seen many a photographer deceived to the point of posting a picture of a flower fly claiming that it is a bee.

The goal of this remarkable imitation is not to fool photographers, of course, but rather hungry predators. Flower flies are delicious morsels of food that any bird would readily accept, but the fear of being stung by this bee mimic may lead him to think twice and skip this prey.

Some flower flies are about the size of a honey bee. The mimicry is so convincing that one of them is called the drone fly. Others are smaller and they may be imitating some of the lesser known and very abundant solitary bees. A few are long and thin and look like wasps, rather than bees.

Mallota bautias, a bumble bee mimic
© 2005 Beatriz Moisset
They can be distinguished from bees or wasps by the number of wings. Bees and wasps have four; flies have only two. The back wings have been reduced to little knobs, called halteres, used for balance. The halteres and the number of wings are hard to see when the insect is flitting about. Even when it rests on a flower, you continue to have trouble because a bee's front and back wings hook up appearing like a single unit.

Flower fly (left), bee (right)
Compare the size of the eyes
and the size and placement of the antennae
© Beatriz Moisset
Other differences are more obvious if you train your eye to see them. Flower flies have enormous eyes and tiny antennae that emerge from the front of the head, rather than higher up as in bees. Also flies are almost hairless and their legs are skinny when compared with those of bees. I hope all this helps you and saves you from embarrassing mistakes. I have seen business cards, article illustrations and even a book cover with a fly passing for a bee. So, if you still don't get them right, at least remember that you are in good company.

Toxomerus, mimics of small native bees
© Beatriz Moisset
In England, flower flies are called hover flies, an excellent description of their behavior. Some people in the US are adopting this name, so you may find either term in the growing literature on these interesting and useful insects.

A colorful flower fly
Helophilus, the sun lover
© Beatriz Moisset
These flies feed on nectar; sometimes they also eat pollen, especially the females who need this protein-rich food to produce eggs. This is why they spend so much time visiting flowers. Because of this habit they often end up carrying pollen from one blossom to another. They may not be as good pollinators as bees, but their role is not insignificant and deserves recognition. For instance, the so called drone fly is used to pollinate greenhouse sweet peppers.

Spilomyia sayi, a wasp mimic
© Beatriz Moisset
Let us applaud the bee impostors, flower flies or hover flies, for their role as pollinators.

For more on pollinators and other flower visitors read the e-book:
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014