A Look at Insect Galls

Have you ever seen weird bumps growing on stems, leaves, buds, or flowers? You might be surprised to learn that these odd growths are not the plant’s idea at all but are caused by a fly, wasp, midge, or other insect.

How Are Galls Formed?

The goldenrod gall, for example, is formed by one kind of gall fly. The female picks out a tender spot on a growing tip of the plant where she deposits an egg and flies off. When the larva hatches out of the egg, it will bore into the plant. As it does so, it excretes a chemical which causes this part of the plant to enlarge into the swelling that we call a gall. Soon the larva is surrounded by this enlarged tissue, essentially its gall house.

Through the summer months, the larva will eat away at the inside of the house. In autumn, the plan dies and the gall turns brown and hard. At this time, the larva digs a tunnel out to the skin of the gall, but does not break through. Instead, it curls up to await spring at which point it will pupate and eventually emerge as an adult gall fly.Insect Galls: A Nature Study @EvaVarga.net

Galls Are Diverse

There are many kinds of galls and each is formed in a different way. In my earlier post, Galls: A Nature Study, I shared the small variety of galls we’ve encountered in our nature studies.

In North America, more types of galls are found on Oaks than on any other kind of plant. They can turn up on many different kinds of plants, however. Including flowers, ferns, and even mushrooms.

 

Symbiotic Relationships

Not all galls are started by insects. Some are caused by mites or nematodes (tiny worms). Fungi and bacteria can also cause galls to form.

Nitrogen-fixing bacteria are microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen (inorganic compounds usable by plants). More than 90 percent of all nitrogen fixation is effected by these organisms, which thus play an important role in the nitrogen cycle.

Even though the galls may deform the plant, they usually don’t do serious harm. Galls also provide a food source for many animals – including woodpeckers and many other insects.

Some galls are even useful to humans. The Bushmen of the Kalahari Desert in Africa make a powerful poison for their arrow tips from crushed gall wasps. In the states, galls that fall from Oak trees are sometimes used by farmers to feed their livestock.Insect Galls: A Nature Study @EvaVarga.net

Bring it Home

Undertaking the activities described below provide students with an opportunity to begin to examine the affect of environmental conditions on galls and insect growth. Students also develop an appreciation and understanding of the complex interactions among plants and animals.

Materials

  • collection jars
  • glue
  • old nylon stockings
  • an intact gall (one without an exit hole)
  • dissecting knife
  • rubber band

Gall Dissection

The larva lies at the center of the gall. Use a dissecting knife or other sharp tool to make an incision in the gall parallel to the stem, but off center. Create a small window so the larva is clearly visible.

Put a little glue around the perimeter of the window and press it against the inside wall of a jar. You will now be able to observe the larva as it develops. Keep track of your observations in your notebook.

Larval Development

Place the gall inside a collection container with nylon stretched over the opening and secured with the rubber band. Make observations of the changes that take place as the insect develops and emerges from the gall.

Most specimens should emerge in approximately 3 weeks.

Inquiry Activities

Design an experiment to explore the effect of different environmental factors such as light, temperature, or moisture. For example, does the amount of light affect the development of the larva?

Once you start looking, you’ll likely find lots of galls. Insect galls are fascinating.

Ever Been to a Moth Night?

 

One of the summer activities we most look forward to is National Moth Week. Our First Moth Night was in 2013 and it has since become a tradition. Last year, we collaborated with the rangers at Whiskeytown National Recreation Area allowing us access to the park after hours. Such a delight to have the entire beach all to ourselves!

Several friends joined us – including a small herd of deer who roamed the area nearby for quite some time – and a park ranger and his friend. We hung a sheet between the trees in the forest area adjacent to the picnic tables on the beach and set up a few lanterns. Before night fell, we did a little nature journaling and enjoyed watching the sun set over the lake as we awaited the arrival of the moths.

moth night @EvaVarga.netWhen it was dark, we began to take note of the insects that slowly arrived.  The kids would proudly exclaim, “Here’s another one!” each time a new insect landed on the sheet. While only a few moths came to visit, we did observe many other insects – many of which were beetles.

We did our best to take photographs of each before they flew away – a task that turned out to be a little more difficult than anticipated – and tallied the numbers for each species.

We stayed until the kids began to get a little sleepy. Ranger Bill closed out the evening with a few delightful stories as his friend quietly played her Native American-style flute.

The next National Moth Week will be held July 18-26, 2015 so start planning your events now!

What is Moth Week?

National Moth Week offers everyone, everywhere a unique opportunity to become a Citizen Scientist and contribute scientific data about moths. Through partnerships with Project Noah, Bug Guide, Xerces Society, Lepidoptera Society, and others, National Moth Week participants can help map moth distribution and provide needed information on other life history aspects around the globe.

Ever Been to a Moth Night? @EvaVarga.netMothing can be done anywhere- at parks, nature centers, backyards and even in towns and cities. Events are taking place around the world – join up or host an event of your own. Learn more at National Moth Week.

This year, National Moth Week will spotlight the Sphingidae family of moths found throughout the world commonly called hawk moths, sphinx moths and hornworms.

Join Us For a Memorable Summer Evening

So invite a few friends and contribute to this awesome project by hosting a moth night of your own.  What happens at a moth night? Basically, you put up a sheet and a light with a bunch of your friends, and sit around and wait for moths.  How simple is that?  And it is so much fun!

Science Milestones: Jean-Henri Fabre

jhfabreJean-Henri Fabre is best known for his popularization of insect natural history. Although a reclusive amateur, with no scientific training, he was an acute observer of insect behavior. He combined his observations (most made in his own backyard) with an easy to read writing style that made his books popular.

The ten volumes of Souvenirs Entomologiques attracted only mild attention when they were first published. Fabre was 84 when the last volume appeared, and he was “discovered” soon afterwards. He was elected to numerous scientific societies, provided a government pension, and even the President of France came to visit him.

Biography

FabreJean Henri Casimir Fabre was a French entomologist born at Saint-Léons in Aveyron, France on December 22, 1823.

He earned teaching certificate at the young age of 19 and began teaching in Carpentras. He was a popular teacher, however, he is probably best known for his study of insects, and is considered by many to be the father of modern entomology.

Much of his enduring popularity is due to his marvelous teaching ability and his manner of writing about the lives of insects in biographical form. He died on October 11, 1915.

One of his most notable discoveries was in regards to insect pheromones. Pheromones are chemicals released from the body of animals and insects that are used to attract mates or relay danger.

L’Harmas, Fabre’s house at Sérignan in the Vaucluse northeast of Orange, was well screened by trees. In a series of key experiments, initially studying the Great Peacock Moth, Fabre found that a female moth could attract males over large distances, even on stormy nights.

It is smell, therefore, that guides the Moths, that gives them information at a distance“.

He deduced that the male antennae had something to so with it, noted that surrounding the female with trays of molecules like naphthalene or lavender oil did not deflect the males from their aim, and observed that males were attracted to an empty cage where the female had spent the previous evening.

Bring it Home

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

Insect Hotels: Nesting Habitat for Mason Bees

The plight of the honey bee and other pollinators is of concern to me.  Insect hotels or habitat for insects is the perfect project for our Roots & Shoots group to show care and concern for animals.  It was also a great introduction  to service learning for my STEM Club kids.  I thereby invited both groups to join us for a day of insect revelry.

I began by introducing the kids to the Mason bee, the common name for a species of bees in the genus Osmia, of the family Megachilidae (Blue Orchard and Hornfaced the best known species). They are so named for their habit of making compartments of mud in their nests, which are made in hollow reeds or holes in wood made by wood-boring insects.

Unlike honey bees (Apis) or bumblebees, Osmia are solitary; every female is fertile and makes her own nest, and there are no worker bees for these species. The bees emerge from their cocoons in the spring, with males the first to come out. They remain near the nests waiting for the females. When the females emerge, they mate. The males die, and the females begin provisioning their nests.

Osmia females like to nest in narrow holes or tubes, typically naturally occurring tubular cavities. Most commonly this means hollow twigs, but sometimes abandoned nests of wood-boring beetles or carpenter bees, or even snail shells. They do not excavate their own nests. The material used for the cell can be clay or chewed plant tissue. One species (Osmia avosetta) in the palearctic ecozone is known for lining the nest burrows with flower petals.

Females then visit flowers to gather pollen and nectar. Once enough provisions have been gathered, she backs into the hole and lays an egg. Then she creates a partition of “mud”, which doubles as the back of the next cell. The process continues until she has filled the cavity. Female-destined eggs are laid in the back of the nest, and male eggs towards the front. Once a bee has finished with a nest, she plugs the entrance to the tube, and then may seek out another nest location.

By summer, the larva has consumed all of its provisions and begins spinning a cocoon around itself and enters the pupal stage. The adult matures either in the fall or winter, hibernating inside its protective cocoon. Most Osmia species are found in places where the temperature drops below 0°C for long durations, like Canada, and they are well adapted to cold winters.

insecthotelsBuild It & They Will Come

Maintaining Mason bee habitats or insect hotels can be a simple, yet powerful way for people of all ages to intimately connect with the awesomeness of nature. Mason bees don’t sting unless they’re squashed or squeezed so they’re kid and pet friendly and don’t require protective clothing or training to work with. Since they’re sociable but solitary, there’s no need to coax colonies into complex forms. A well-designed and well-built habitat with ample nearby pollen sources will naturally attract mason bees, can allow intimate year-round observation of their lifecycle, and especially for teachers, parents and community garden programs be a powerful real-world teaching tool.

Mason bees are increasingly cultivated to improve pollination for early spring flowers. They are used sometimes as an alternative, but more often alongside European honey bees. Most mason bees are readily attracted to nesting holes; reeds, paper tubes, or nesting trays. Drilled blocks of wood are an option, but do not allow one to harvest the bees, which is vital to control a build-up of pests.

I found the post, Housing Mason Bees at Bees, Birds, & Butterflies particularly useful as I researched the how-tos for building insect hotels.  You can also purchase pre-made insect hotels from a variety of sources.  For example, Esschert Design Bee House. The kids had a great time building their own and it allowed their creativity to show.  Most of the kids recycled materials (soup cans, two liter bottles, etc.) to create a cylinder to hold bamboo and paper tubes. Many of the kids stated they wanted to build a wooden frame around their tubes and planned to finish their projects at home.

Attract Pollinators with Native Plants

To help bees and other pollinating insects (butterflies) you should provide a range of plants that will offer a succession of flowers, pollen, and nectarthrough the whole growing season. Patches of foraging habitat can be created in many different locations, from backyards and school grounds to golf courses and city parks. Even a small area planted with the right flowers will be beneficial those with small yards shouldn’t hesitate to do their part.

  • Use local native plants.
  • Choose several colors of flowers; particularly attractive to bees are blue, purple, violet, white, and yellow.
  • Plant flowers in clumps.
  • Include flowers of different shapes. Bees are all different sizes, have different tongue lengths, and will thereby feed on different shaped flowers. 
  • Have a diversity of plants flowering all season.

Contact your local extension agency to learn what plants are native to your area.  You may also find useful fact sheets provided by The Xerces Society.

Additional books & resources:

Homegrown Learners

STEM Club: Arthropods

We wrapped up our study of invertebrates this week with a focus on the Arthropod Phyla.  I opened class with a short lecture portion, again encouraging the kids to take notes on the chart I had created the previous week or directly into their notebook.

Characteristics:

  • hard exoskeleton which they molt several times as they grow
  • bilateral symmetry
  • jointed appendages (legs and antennae)
  • largest animal phyla – more arthropods than any other animal

Examples:

  • insects – 3 pairs of legs
  • arachnids (spiders & mites) – 4 pairs of legs
  • crustaceans (crabs & lobsters) – 5 pairs of legs
  • millipedes & centipedes.

I had stations set up around the room introducing the kids to the diversity of insects (each station focused on a characteristic of a specific insect order).  Each station had a card (with printed instructions), a photographs, and at least one actual specimen to observe with a hand-lens.  I have created a slide presentation that you can use to simulate these stations with your students.  Though helpful and certainly of interest to the kids, the actual specimens are not required.  You can download the presentation here:  Insect Classification.

hands-on science activity

Upon concluding the first activity, I then introduced the inquiry portion of the lesson.  I had purchased in advance several live arthropods – 3 Madagascar Hissing Cockroaches (Class Insects, Order Blattodea), Bumblebee Millipedes, and a dozen or so pill bugs (Class Malacostraca [Crustacea], Order Isopoda).  The kids were divided into small groups and instructed to devise a simple experiment to test an experimental question.  For example,

What food(s) do the cockroaches prefer? 

What temperature do the pill bugs prefer?

Do pill bugs prefer light or dark?

isopod inquiry activity

Each group was allowed to utilize any number of the things I had on hand to set up their experiment – cardboard boxes, paper towels, ziplock baggies, aluminum foil, a variety of food (oatmeal, grapes, carrots, crackers, etc.)  I was delighted to see how well the kids worked together in the limited time we had to complete the activity.  Each group was able to quickly decide upon a question and devise a way to test their hypothesis.  However, we did not have the time to carry out different trials (repeat the experiment) and regardless, the sample sizes were too small to make any conclusions.  The activity provided me with a good understanding of what they understood about inquiry activities, however.

Mud Daubers

A month or so ago, we observed a few mud dauber wasps in the vicinity of our garage.  As we watched them fly about our heads, we also came to realize there were several light brown colored blobs of mud plastered on the walls of the garage.  My husband, ever so diligent, wanted to spray them.  I pointed out, however, their ‘homes’ were encased in mud and it wasn’t clear how the chemical would penetrate the walls of their structure even if I was in agreement with his method (which I was not).  He thereby left the disposal of these potentially frightening, thin-waisted stingers to me.

What was I to do?  Google, of course!  Within a few moments I came across a short and sweet little video on eHow of an licensed exterminator (at least I can presume he was a professional) not only explaining how to easily remove the mud case from the walls of the garage but also providing a wealth of information about these tiny architects.

I thereby scraped the few structures we had observed … all but one crumbled into dirt, revealing the cells within which resided the young wasp larvae.  I immediately called the kids over and we marveled at the structure as well as the developing insects.  In one cell, we also observed a number of small, plumb spiders – an insect pantry of sorts.  🙂

A few weeks later, I downloaded the Handbook of Nature Study June newsletter and discovered to my delight that one of the challenges focused upon yellow jackets or mud daubers.  How timely!   We hadn’t thought to journal our discovery earlier .. now we had the perfect inspiration.  We thereby pulled out our journals and sat down at the computer to look again at the photograph we had taken when we disposed of the nest earlier.  
The kids were not keen on sketching the adult insect, “… too scary!” was their comment.  They thought my sketch was “freaky” enough.  I just love the labeling that #2 added to his sketch (his is shown prominently on top). He was confidant and took the initiative to label his without a single request from me.  It is impressive to me – and heartwarming too – that he used his own spelling.  He took the lead … and #1 followed his example.