Tuesday, July 12, 2016

Pollinator Gardens do Double Duty

Syrphid flies. Pollinators and biological controls. Their larvae feed on aphids
© Beatriz Moisset

More gardeners are learning about pollinators and creating habitat for them. It warms my heart when I see them selecting plants beneficial to pollinators, converting portions of the lawn into flower plots, cutting down on pesticides, and creating the right conditions for pollinators’ nests. Many gardeners are learning to be grateful to pollinators for their services. Some are familiarizing themselves with the most common ones. This is a healthy trend.

Syrphid fly larva devouring aphids
© Beatriz Moisset
An additional advantage of pollinator gardens is that they serve another useful function. Many other beneficial insects depend on pollinator gardens and, in turn, gardens and farms profit from their presence. I am referring to predators and parasites of plant-eating insects. Such beneficial insects have earned the name of biological controls, or biocontrols for short. Many biocontrols need nectar, or nectar and pollen, during part of their life cycle. Some of them prefer to eat insects but can survive on nectar and pollen in the absence of their prey. Thus they are ready to spring to action when the unwanted pest arrives. Gardens lacking on floral resources are not as well protected against pests.

Tachinid fly, Trichopoda pennipes. Its larvae feed on insects
© Beatriz Moisset
The extra bonus of growing a pollinator garden became apparent in studies done by Cornell University. Apple growers could cut down pesticide treatments from ten to two or three a year when they started growing plants for pollinators.

Robber fly, Laphria thoracica, a formidable hunter of insects
© Beatriz Moisset
It is a great thing that the needs of pollinators and those of many biocontrols overlap. Syrphid flies illustrate this point. The adults are bee-like and hover over flowers, earning them their common names, flower flies or hover flies. They feed on nectar and pollen and manage to do some pollination. Their larvae are little green maggots that feed voraciously on aphids. They frequently escape notice. I have learned to check aphid colonies and frequently I find some of these maggots doing what they do best, getting rid of aphids.

An ichneumonid parasitic wasp
Its impressive appendix is an ovipositor (egg laying organ), not a stinger
So there is nothing to fear from this wasp
© Beatriz Moisset
One of the solitary predatory wasps, potter wasp (Eumeninae)
hunting a caterpillar hiding on the flower head
© Beatriz Moisset
Here are a few other examples of biocontrols that prosper in pollinator gardens: Tachinid flies, some of which are hairy, robust and rather ugly, while others are elegant and colorful. All lay their eggs on or in other insects and help control many pests, even gypsy moths and Japanese beetles. Robber flies are fast fliers and skillful at pouncing on unsuspecting victims. Wasps are great garden helpers, both the parasitic ones, which lay eggs on other insects, and the predatory ones, which catch prey to feed their babies. The adults feed primarily on nectar and pollen. It is good to remember that parasitic wasps don’t sting and that most predatory ones are not inclined to do so. In most cases there is no need to fear these wonderful biocontrols. Assassin bugs have front legs that resemble those of praying mantises and, like them, use them to grasp their prey with a swift movement. Not all stink bugs are plant pests; the predatory ones feed on the pests themselves. The merits of lady beetles as eaters of aphids and other soft bodied insects hardly need mentioning. Both larvae and adults feed on these pests. The adults are also fond of nectar and pollen. Other beetles worth mentioning are the soldier beetles, so called because their colors and pattern resemble those of old army uniforms. They are frequently seen visiting goldenrods.

Assassin bug, Zelus luridus
© Beatriz Moisset
Among the plants that feed both pollinators and biocontrols are many Asteraceae, such as coneflowers, coreopsis, yarrow, and goldenrods. Other families include Apiaceae, the carrot family, Lamiaceae, the mint family, Euphorbiaceae, the spurge family, and Fabaceae, the pea family. The best information on planting for pollinators by region is provided by the Pollinator Partnership. You can also find some information in Attracting Beneficial Insects with Native Plants.

Soldier beetles, Chauliognathus
© Beatriz Moisset
In summary, your pollinator garden does double duty, helping pollinators and also biological controls. Perhaps we could say that it does triple duty, as many of the flowers are beautiful and we get to enjoy them too. Happy plantings!

Polished lady beetle, Cycloneda munda
© Beatriz Moisset
References


© 2015, Beatriz Moisset. First published in Native Plants and Wildlife Gardens. 4/7/15

Friday, July 01, 2016

The Twin Brooks of Yesteryear


Two small streams traverse our condominium and they give it its name, Twin Brooks. They escape notice by most visitors because they are no more than tiny rivulets that a young person, not me, could cross in a single jump. Moreover, all the landscaping has done much to hide them out of sight. Probably a good part of the water runs through underground pipes. But Nature persists as best it can and a good observer perhaps could imagine what the land looked like before all the earth moving, paving and construction that could place in recent times.
 

Where the two brooks meet, a small pond is present. Ducks and geese raise their families there some years. An occasional blue heron visits the pond and manages to make a meal of some little fish. Also, a muskrat hangs around the edge of the water.

I wonder what the land was like a few thousand years ago before Europeans arrived and populations grew and grew to what they are nowadays. There were Native Americans then, tribes distributed across the land. The ones living here were the Lenape (or Lenni-Lenapi). Were some of them camped in the Twin Brooks site either temporarily or generation after generation? Do I walk on their steps sometimes?

I search for information on the original residents of this land and learn that the Lenape tribe covered part of Delaware, eastern Pennsylvania, all of New Jersey and a southeastern part of New York state. The region was known to them as “Lenapehoking,” which meant land of the Lenape. These Native Americans had a matrilineal system, that is children belonged to their mother's clan, from which they gained their social status and identity. Male leadership was passed through the maternal line and elder women could remove leaders they didn't approve of. Not exactly equal rights but far better than the condition of European women of those days.

So, I try to imagine the Twin Brooks family or families that occupied this area long before our condominium was built and long before I moved here. Perhaps they built their wigwam at the spot where the two streamlets met. Did they grow the Three Sisters –corn, beans and squash– where we have a parking lot? Are there some broken clay shards buried somewhere? Perhaps a little girl lost her doll exactly under my bedroom, the doll her grandmother lovingly made using corn husks and strings. I have no doubt they hunted deer and turkey nearby. Rarely a lost deer wanders into our property, desperately looking for better cover and finding only pavement, traffic and frightening noises.
 

They must have gathered berries. Still some berry shrubs grow here and there. Chestnuts must have been an important part of their winter food. It is sad to think that practically no chestnut trees are left because of a terrible blight accidentally introduced from overseas.

European colonists coveted the land when their population kept growing, so they relocated the Lenape Indians a couple of centuries ago. “Relocated” is just a wishy-washy way to say that the original residents of the land were robbed of their rights, uprooted and sent to an uncertain fate to the Indian Territory in Oklahoma. There, they had to survive as best they could, making do with limited resources and competing with other tribes already present in the area.

I wonder what we mean when we sing: “This land is my land.”

Thursday, March 12, 2015

Follow the Monarchs

Monarch Butterfly Migration Map

Follow the migration of the monarch butterfly with the help of these maps provided by Journey North. Bear in mind that the subspecies of monarch, Danaus plexippus plexippus, is the migratory one, the one we are familiar with in the United States and Canada. There are 5 non-migratory subspecies in the neotropical region - portoricensis in Puerto Rico; leucogyne on the Virgin Islands; megalippe in Cuba, the Bahamas and the Caymans; tobagi on Tobago, and nigrippus in the Andes. We know next to nothing about these subspecies and their conservation status. Some may be more endangered than “our” monarch. We just don’t know. Some consider all the non-migratory monarchs as members of a single subspecies, megalippe. Still others think that there are 8 subspecies.

The southern monarch, Danaus erippus, of southern South America is closely related and similar looking. It was considered a subspecies of Danaus plexippus, but now it is regarded as a separate species. It is also migratory to some extent. Very little is known about its migration.

Learn more about the present status of the migratory monarch subspecies, Danaus plexippus plexippus:
Conservation Status and Ecology of the Monarch Butterfly in the United States

Sunday, November 23, 2014

Food Chain in the Milkweed Patch



Common milkweed. © Beatriz Moisset
The common milkweed teems with life. Numerous insects feed on leaves, stems, and roots or sip nectar from their flowers. It is ironic that a plant so well protected by powerful toxins and sticky sap behaves like a magnet for a large assortment of creatures. The best known dependent of the common milkweed is the monarch butterfly, but there are many others that deserve our interest. Many species have found ways to overcome the defenses of this plant. They have developed resistance against the toxic cardenolides and methods to avoid the milky sap.

The herbivores are in turn eaten by other insects or spiders, which may fall prey to still other carnivores. It is worthwhile to examine one of these so called food chains or food webs.

Oleander aphids on common milkweed. © Beatriz Moisset
One milkweed feeder, the oleander aphid, has become incredibly common in recent years. This bright yellow-orange aphid was accidentally introduced in this country with oleander plants, widely used in ornamental gardening. It established itself successfully and became adapted to milkweeds. It multiplies in huge numbers near the end of the season. It can do so because females reproduce parthenogenetically, that is without help from males.

Parasitized or mummified aphids. One wasp left the corpse through a round hole. © Beatriz Moisset
This aphid has few enemies. One of them is a tiny parasitic wasp. The mother wasp lays one egg inside a growing aphid and the larva completes its entire life cycle inside the unfortunate host. By the end of the aphid's life, it becomes dark, rounded and dried up. We call that a mummy. The fully grown wasp cuts out a round hole and emerges ready to start parasitizing other members of the aphid colony. It isn't easy to see the wasps, but almost every aphid colony has some of these mummified bodies. So you know that the parasitic wasps have been around.

Parasitic wasp. © Beatriz Moisset

Lacewings, lady beetles and syrphid flies also feed on aphids. Their stories are worth telling but we'll let them be for now.

The food web does not end there. Not surprisingly, many predators visit the milkweed patch in search of animal food. Parasitic wasps seem to be a delicacy among some flies. I have found members of two different families of predatory flies dining on the wasps.

Robber fly (Taracticus octopunctatus) feeding on a parasitic wasp. © Beatriz Moisset
One is a member of the family of robber flies, Asilidae. The name describes the members of this family well. They are seen pouncing mercilessly on their prey. One of them is Taracticus octopunctatus (no common name), a slender, hunchbacked fly with large eyes.
Long-legged fly feeding on a parasitic wasp. © Beatriz Moisset
Another one is a longlegged fly, Condylostylus, a shiny metallic green fellow, with long skinny legs. Parasitic wasps are part of its menu.

I marvel about this food preference. Evidently, these flies look down on the most abundant food nearby, the aphids, and go for the far less common parasites. Perhaps, the latter have less cardenolides than the aphids and this is why the predatory flies prefer them as food.

Longlegged fly caught by a spider. © Beatriz Moisset
A second layer of predation is added to the one just described. A spider feeds on a longlegged fly. We can summarize this food chain this way:
Milkweedaphidparasitic wasppredatory flyspider

Will a bird sweep by and eat the spider? Will it in turn fall prey to a hawk or a snake? How many steps can be added to this food chain? Common milkweed feeds many members of the wild life directly and indirectly. The links of this food chain are numerous.

More on milkweed dependents and visitors

Monday, November 03, 2014

Wasps, Motherhood and Ultrasound

Female Pimpla wasp locating a moth pupa. © 2014 Beatriz Moisset

A slender wasp lands on a plant stem and starts gently tapping it with the tips of her thread-like long antennae. Tap-tap-tap, she goes up and down the stem. She may abandon her search and repeat the same process on another plant, and another. When she finally finds what she is looking for, the tapping becomes more pronounced and remains concentrated in a single spot. A Pimpla wasp is delicately built, glossy black with bright orange legs. Its body ends in a sword-like projection used for egg laying and called ovipositor. This is how we know she is a female. Her methodical activity is a preparation for motherhood.

At a hospital an expectant mother is having a sonogram of her fetus. The technician gets the equipment ready, applies gel to the mother's belly and runs a wand over it. The image of the baby inside the womb emerges in the monitor. The invisible becomes visible through the magic of ultrasound technology.

Ultrasound of a fetus. By Pacres. Flickr
These two unrelated events have something in common. The expectant wasp mother is also using ultrasound for the benefit of her progeny. The amazing thing is that she and her ancestors have been using this technology for millions of years. Even more amazing is that she carries all the needed equipment in her tiny body. One big difference is that she is not observing her unborn baby but locating the food her baby will need. Other wasps have an easier time. They hunt for caterpillars, which are relatively easy to find because they make noises when munching away. But a pupa remains perfectly still and requires special equipment to be detected.

The ultrasound equipment used to see a fetus inside the mother's womb consists of a machine that produces high-pitch vibrations, beyond human hearing, and a sensor, called a transducer, that collects and interprets the sounds bounced back from the mother's body, her placenta, and the little body curled up inside.

The Pimpla wasp vibrates her body in a special way, producing ultrasound waves which she transmits to the plant surface through her antennae. She absorbs the bounced back ultrasound through her legs where some tiny organs, called genua, collect information on the shape, size and location of its quarry. An image develops in her minuscule brain, an image similar to the ones we have all seen of unborn babies inside the womb. Now she knows exactly where to lay her egg.

Pimpla wasp, female. © 2014 Beatriz Moisset
She bends her abdomen and points the sharp ovipositor toward the hiding moth pupa. She inserts an egg on it and leaves. Her mission accomplished, she starts looking for other occult cocoons to lay more eggs on them.

We marvel about bats and dolphins using a similar process, echolocation. It is remarkable that a tiny insect can also use a version of this complicated technology.

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Sunday, August 17, 2014

Ladybugs, Praying Mantis, and other So-called Beneficials. Are They?

The native polished lady beetle, a good one
I recently published an article on ladybugs, better called lady beetles, in Native Plants and Wildlife Gardens. My purpose was to explain that not all lady beetles are beneficial. Unfortunately some are introduced species which disrupt the ecosystems, competing with and even killing some of the native ones.

Spotted lady beetle larva (Coleomegilla maculata)

In writing the article and later reading people's responses, a more serious problem caught my attention. Companies that sell lady beetles are causing more damage than good. Well-intentioned gardeners buy them without realizing the consequences of introducing non-native lady beetles or the pests that they carry.

An invasion of Asian lady beetles. More trouble than they are worth
This led me to want to learn more about other bio-controls or biological pests controls being sold to unwary gardeners. I will be writing in the future about praying mantis and their commercialization. This seems to be a bigger problem than that of lady beetles. For now, just look at these pictures. More coming up later on.

Tenodera sinensis sinensis (Chinese Mantid)


© Beatriz Moisset. 2013


Friday, July 04, 2014

Hidden Life on a Pear Tree



Bradford pear in bloom, attracting numerous pollinators
© 2014 Beatriz Moisset
Spring finally arrived, although a little later than usual. At the end of April, the Bradford pear trees in front of the Abington Library were in full bloom, white clouds against a sapphire sky. Hordes of little bees eagerly visited the sweet flowers.

Pollinators were not the only visitors to the trees. Surprisingly, life was also present in places you wouldn't think to look at. A cluster of bright yellow dots in a bark's crevice caught my eye just by chance. Afterwards, I began to see many similar clusters, partially hidden by the bark's irregularities. I knew them as lady beetle eggs, so I wasn't surprised to see some adult lady beetles engaged in romance or in search of potential nurseries for their babies.


Lady beetle eggs
© 2014 Beatriz Moisset
 A solitary green aphid painstakingly climbed the tree trunk, probably in search of tender shoots to feed on its juices. What was it doing so far from its traditional food? Perhaps, it had fallen to the ground and, obstinately, was engaged in the arduous voyage back to distant branch tips.

I puzzled at the lady beetles' choice of egg-laying sites. The tree trunk may offer refuge for the eggs, but not food for the newborns. The tiny larvae would have a long way to go to find nutritious aphids. Perhaps, just like the lost aphid, they could manage the perilous trek successfully.

I visited the trees a week later. They were still blooming, although slightly past their peak. I looked for the lady beetle eggs and found many of the clusters still in place. Some had darkened, a sure sign that the larvae inside would soon emerge, hungry for aphids. Others had become food for unknown predators and were gone.


An incipient aphid colony
© 2014 Beatriz Moisset
 Once again, I wondered where they would find food and looked at the new growth, the clusters of flowers which were already beginning to leaf out. Aha! Just as I suspected, the green aphids were there, small colonies of young and adults, wingless and even some winged ones. I would have never noticed them if I hadn't suspected their presence because of the lady beetles.

Aphids have a way of multiplying at great speed. One female can produce many babies in a mere week and the babies start reproducing in an equally short time. The small colonies I observed would become huge by the time the new leaves reached full size. They would be numerous enough to damage the new growth.


Aphid in search of food
© 2014 Beatriz Moisset
Would something keep the aphids in check? The mentioned lady beetles had their job cut out for them. But they would need lots of help and I was pleased to see other aphid enemies. I caught a glimpse of a parasitic wasp. These tiny wasps lay their eggs inside aphids and their larvae feed and kill their hosts in the process. Another great helper became apparent later on, on further observation. Some minute greenish grubs were thrashing about in the midst of the aphid colony. A syrphid fly had chosen this place to lay her eggs. The recently emerged blind and apparently helpless larvae were busy devouring their favorite food, juicy aphids. They grow fast on this nutritious diet and soon metamorphose into small flies, ready to lay more eggs.


Syrphid fly maggot feeding on aphids
© 2014 Beatriz Moisset
 The accidental sight of the lady beetle eggs led me to the related findings, aphids and their predators—an entire mini-ecosystem well hidden in bark cracks and flower clusters of a pear tree. A month later, I visited the trees again and found no traces of this entire food chain. The stems appeared too tough for the aphids; the winged ones had moved elsewhere. The lady beetles and other predators also took their leave in their perennial search for nourishment.

Aphids in the web of life

List of articles

© Beatriz Moisset. 2014