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

Sunday, March 2, 2014

The Importance of Native Pollinators

Bumble bee visiting a sunflower. © 2010 Beatriz Moisset
At the risk of repeating myself, I want to discuss once again the widespread erroneous belief that we depend entirely on honey bees for the pollination of one third of our food and that we would all die if they were to disappear. Honey bees are not the only pollinators. We must value all the others and we should learn to take advantage of them for our crops' pollination.

We must remember that 4,000 species of native bees populate this country; 20,000 the entire world. They vary in size, appearance, season of activity, flower preference. . .  Some live in colonies similar to those of honey bees, but most are solitary and nest in holes in the ground or in hollow tubes inside soft pitted canes or in holes left behind by beetle larvae.

All of them combined are tremendously important, not just for the pollination of wild flowers but also of some crops. In fact, all the crops pollinated by honey bees could be taken care of by one or another of the numerous species of wild bees.

A few examples of the marvelous things native bees do

*Bumble bees and several solitary bees pollinate tomatoes, peppers and eggplants. Only they know how to manage their flowers. Honey bees cannot do it

*The alfalfa bee and the alkali bee pollinate 80% of the alfalfa flowers they visit. Several bumble bees do just as well. The batting average of honey bees is a mere 20%

*A single southern blueberry bee can pollinate $20 worth of blueberries (probably more at current rates). Honey bees don't come even close

Osmia  sp., a mason bee. © 2007 Beatriz Moisset

*An acre of apples can be pollinated by 250 female orchard mason bees. This task would require 1.5 to 2 honey bee hives—approximately 15,000 to 20,000 bees

Squash blossom. © 2014 Beatriz Moisset

*Squash bees are up early in the morning, when squash flowers are at their peak. Later on, when bumble bees and honey bees arrive, most of the pollination has already taken place

*When the weather is bad, too cold or wet, some native pollinators go out anyway. A few work before sunrise or after sunset. The honey bees prefer to stay home under these conditions

An assortment of pollinators provides a degree of insurance. When the population of one species  declines, as it is bound to happen some years, other species take over the slack. This is one of the advantages of diversification. We have depended for too long on just one species.

Despite the advantages of this variety of native pollinators, farmers often resort to honey bees because the wild pollinators are, well, wild, not easily controlled. Honey bees provide a large task force that can be managed and transported where needed. They are perfect for large monocultures, with only one kind of food temporarily available and nothing else the rest of the year.

We shouldn't ignore the contributions of native bees. They can do a superb job at small or medium sized farms. Managing them would require a healthier habitat and less pesticides. A polyculture, the opposite of a monoculture, would also be important.

We are reaching a point in which we cannot rely entirely on just one species of pollinator. The task of changing cultivation practices is huge but it can be done and it needs to be done. The Xerces Society and some universities are committed to developing the ways of putting native pollinators to good use. The results have been highly encouraging.

Long-horned bee on sunflower. © 2007 Beatriz Moisset


Additional readings

Farming with Pollinators, the Xerces Society
Wild Pollinators, Agriculture’s Forgotten Partners. WildFarm Alliance
Native Pollinators. Wildlife Habitat Council

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014 

Saturday, February 22, 2014

Don't Underestimate the Native Pollinators

Honey bee and several native bees on flowers of fruit trees
© Beatriz Moisset
 The concern for honey bees has exploded in recent years. A day doesn't go by without a new article on the media or comments on numerous nature blogs. Some are agonized cries of help with words such as: Save the bees to save our food supply! Honey bees are going extinct, we are next! Almost completely lost in the shuffle are native pollinators, namely the 4,000 species of bees in the US.

Most of the public is unaware that native pollinators could supply a substantial amount of crop pollination. In many instances one or another native bee or an entire cadre of them results in more efficient pollination than that of honey bees. Here are a few examples:

In an apple orchard, 250 orchard mason bees can do as much as 15,000 to 20,000 honey bees. Squash bees are early risers and are likely to do more pollination of pumpkins and squash than the late arrivals—honey bees and bumble bees. The Southeastern blueberry bee, Habropoda laboriosa, is capable of pollinating $20 worth of blueberries in her lifetime. Many native bees work in wetter or colder weather than honey bees. The alkali bee and the non-native alfalfa leaf cutter bee pollinate a higher percentage of visited flowers than honey bees do. Some small orchards and vegetable fields get most of their pollination done by native bees.

Many native bees practice buzz pollination,
needed by tomatoes and other crops
© Beatriz Moisset
All and all according to some studies, native bees provide $3 billion worth of pollination to agriculture, while honey bees' contribution is valued at $15-18 billion. If we put native bees to work, we could reverse these proportions. Perhaps the best way out of the so-called honey bee crisis is to find the way to take better advantage of the other bees. How difficult would that be?
A hundred years ago native bees played an important role on crop pollination. As far back as seventy or eighty years, several authors noticed that bumble bee and solitary bee populations were dropping. This loss was most noticeable in larger farms where sometimes fruit or vegetable yield suffered by the absence of pollinators. Nobody seemed terribly concerned as long as the honey bee could be brought into service. Some observers knew that native bees were more efficient in many cases, but felt that the ease with which honey bees can be managed compensated for this drawback.

Some native bees are just as efficient as honey bees
at pollinating fruit trees
© Beatriz Moisset
Intensive farming grew as did the need for pesticides, and beehives started to be transported long distances and in large numbers to do their duty. It was the birth of the pollination industry involving beekeeping practices far removed from what would be considered natural. It shouldn't surprise us that such an unsustainable system is causing troubles for honey bees.

Can we bring native pollinators back after they continued to lose ground for the past century? Are there enough left around to take over the task of pollinating our crops? Even without statistics, we can be sure that only a tiny fraction of the previous populations remains. Perhaps, some species are precariously hanging on the verge of extinction or have already disappeared.

Dead solitary bee © Beatriz Moisset
No species takes the road to extinction willingly. Every creature, large or small, fights tooth and nail, or mandible and tarsal claw as the case may be, to stay alive and procreate. A few years ago, an entomologist found a miner bee's nest in a flower pot in his backyard. Another bee expert encountered a rare species of bee, regarded close to extinction, in the very heart of Washington DC, in a butterfly garden at the Washington Mall. With remarkable tenacity, these little survivors had managed to find just enough resources and shelter to raise their families in the middle of the concrete jungle.

We should not give up hope. Native pollinator populations can be brought back to the levels of yesteryear; perhaps then they can resume pollinating the crops that feed us.

Pollinators. © Beatriz Moisset.
Update, April, 2014. I followed some published reports when I said "native bees provide $3 billion worth of pollination to agriculture, while honey bees' contribution is valued at $15-18 billion." However this may be shortchanging native pollinators. Perhaps they do a lot more. A publication by Claire Kremen states that in California  native pollinators are responsible for $2.4 billions and honey bees for $3.9 billions. In other words, in that state native pollinators are responsible for about 40% of all agricultural pollination. I will keep searching the truth.

List of articles

Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014 

Monday, February 10, 2014

Alfalfa Pollination

What is the most important insect-pollinated crop? Not a fruit or a vegetable but alfalfa. Yes, alfalfa, not because we consume large amounts of their sprouts, but because cattle needs this food. Thus: no alfalfa, no beef or milk.

This crop was first introduced in California during the gold rush. Alfalfa farming grew from there at a steady pace to what it is today, the third largest crop, after corn and soy bean. A few species of bumble bees and solitary bees took a look at this exotic flower, found it to their liking and proceeded to pollinate it. It wasn't a big leap; this plant's blossoms resemble those of other members of the pea or bean family. The native pollinators were familiar with bean flowers and adapted easily to the new arrival.

Alfalfa blossom. H. © Zel. Wikicommons
Peas, beans, alfalfa, clover and several other plants have butterfly-like (papilionaceous) flowers. The lower petals form an enclosure, shaped like the keel of a boat. This structure holds the sexual parts, the anthers and pistil. When an insect lands on the flower, a trigger mechanism makes it snap open or trip the flower. This is how pollination is accomplished.

Honey bees were not present in California when the earliest fields of alfalfa were cultivated. The first beehive arrived in 1853, just one solitary hive; a few others had died in transit. It took many years for the honey bee populations to build up to significant levels. This didn't matter because the wild bees did an excellent job.

New Zealand wasn't so lucky when it started growing alfalfa to feed the recently introduced cattle. The few native pollinators were stumped by the new flower. They lacked the necessary equipment and dismissed the strange blossoms. Year after year, hay grew luxuriantly, but no seeds. Alfalfa growers resorted to importing a few species of bumble bees from Europe to cut down the expenses of having to buy seed every year. Thus, industrious bumble bees saved the day in that country.

Scotch broom, a papilionaceous flower, being tripped. © Beatriz Moisset
 Honey bees detest the rough treatment alfalfa flowers subject them to and soon learn a trick of their own. They enter the flower from the side and help themselves to nectar without tripping its mechanism. Only na├»ve, youthful ones pollinate flowers. Despite the honey bees' poor performance, most alfalfa farmers resort to them because of the convenience in using a managed species.

In addition to the honey bee, two other species of alfalfa pollinators are managed to some extent and used commercially. They are the Japanese alfalfa leafcutter bee and the native alkali bee.

The populations of native bees have been severely reduced in the last one hundred years largely because of intensive agriculture. Restoring their numbers and putting them to work in alfalfa fields would be an arduous task but a worthy one. Some farmers find that, when they include flowering and nesting site places in their fields or orchards, the health of the crop improves and the need for pesticides diminishes. Thus, alfalfa pollination could be done entirely and more efficiently by native bees. This form of agriculture would be more sustainable than the present methods.

List of articles
Bring Back the Native Pollinators
Will We all Die if Honey Bees Disappear?
Growing Insects: Farmers Can Help to Bring Back Pollinators
Organic Farming for Bees

© Beatriz Moisset. 2014