insects – My Chicago Botanic Garden

Dragonflies capture summer

Summer won’t be over for a while in my book—not as long as there are dragonflies around. I think I’ve seen more dragonflies this year at the Chicago Botanic Garden than I have in the past ten years combined. The quick, strong fliers seem to be everywhere.

Female Eastern Pondhawk — Eastern pondhawk dragonfly, female. Most dragonflies have very different-looking males and females. This one was in the Native Plant Garden. Photo ©Carol Freeman.

Some of the dragonflies migrate south toward the Gulf Coast through September and maybe beyond. With the help of citizen observers, scientists are studying the migration patterns of this fascinating insect, which has a near 360-degree field of vision that helps it avoid predators.

The most abundant dragonfly I’ve seen this year is the Eastern pondhawk, with blue dasher dragonflies coming in a close second. I’m also seeing quite a few damselflies, which are generally smaller and more thin-bodied than dragonflies and tend to hold their wings above their bodies. (See my blogpost Damselflies 101 for more information.)

Female Blue Dasher Dragonfly — Blue dasher dragonfly, female. She looks very different from her male counterpart. Photo ©Carol Freeman.

Male Blue Dasher — Blue dasher dragonfly, male. Hanging out on the waterlilies. Photo ©Carol Freeman.

Dragonflies and damselflies, both in the order Odonata, can spend several years as aquatic nymphs before they emerge into the beautiful winged insects we see on land, which is why you will often see them around water. They are fierce hunters in both stages. They don’t bite or sting humans, though.

Green Darner — The common green darner dragonfly is one of the first dragonflies to emerge in the spring, and one of the species that can be found migrating in huge swarms in the fall. Photo ©Carol Freeman.

Dragonflies can be found here from March through the first hard freeze in the fall. Right now, you might even be lucky to find yourself in the middle of a migrating swarm of green darners, black saddlebags, or wandering gliders as they head south. About 90 different odonates can be found in the Chicago area. Each one is a delight to behold.

Eastern Amberwing — Eastern amberwing dragonfly, male. This is one of the smallest dragonflies in our area, at just more than 1 inch long. Photo ©Carol Freeman.

Widow Skimmer — Widow skimmer dragonfly, male. This is one of the larger, flashier dragonflies, and it is easy to identify. Photo ©Carol Freeman.

Eastern Forktail Damselfly — Eastern forktail damselfly, female. This is the most common damselfly in our area, and it can be found in the Dixon Prairie. Photo ©Carol Freeman.

Dragonflies are territorial and will often chase off other dragonflies, only to return to their favorite perch. A favorite place to find them at the Garden is around the waterlilies and lotus blossoms, but you can spot them throughout the 385-acre grounds. Drop by and keep an eye out for the dragonflies near the late-summer blooms.

Skimming Bluet Damselfly — Skimming bluet damselfly, female. This is a small, delicate damselfly found in the Dixon Prairie.
Photo ©Carol Freeman.

Slender Bluet Damselflies — Slender bluet damselflies, getting ready to lay some eggs. I found this pair along the shoreline next to parking lot 5.
Photo ©Carol Freeman.

Pest Alert: Know Your Galls

A gall, tumor, or burl is an abnormal growth on the leaves, stems, roots, buds, twigs, or crown of a plant. In most cases, the gall is unsightly but not damaging. In small plants, the vascular flow of water and food can be restricted, causing poor growth and making the plant more susceptible to other stresses. A large tree can be weakened by an infection over many years. Nematodes, mites, and insects cause 95 percent of galls. Bacteria and fungi cause the remaining five percent. In most cases, the gall-making organism can be identified by observing the structure of the gall and the species of the host plant.

Galls on a Flower — Galls on *Rudbeckia laciniata* ‘Herbstsonne’

Fungal galls are spread by ascospores in wind and water and can be found on many common trees including oak, maple, and common privet. Black knot affects many species of the genus Prunus—particularly cherries and plums.

Crown gall is a common problem caused by bacteria. The disease is spread by infested soil, transplants, or contaminated tools. The bacteria enters the plant through wounds caused by cultivation, pruning, or insects. Easy prevention methods are to plant only healthy stock (no suspicious bumps), to clean pruners between use on each plant with alcohol or a 10 percent bleach/water solution, and to take care not to injure plant stems. The bacteria stays active in the soil even after removal of infected plants, so place new, healthy stock elsewhere. Remove and destroy all infected plants. Galls caused by bacterial and fungus are more prevalent during wet years.

A gall can form in response to toxins injected during insect feeding or egg laying, or around a feeding larva. The hackberry leaf gall is caused by psyllids, which are tiny winged insects. Galls formed by insects usually do not affect the overall health of the tree unless they experience early defoliation over the course of many years. Parasites are an important control of this pest. Many oak galls are caused by gall flies and generally are not detrimental. A severe twig infection can, however, cause severe injury and even death. Spruce galls are often caused by several species of an aphid-like insect. If only a few galls are present, they can be cut off and destroyed before the insects emerge in midsummer.

Leaf galls on maple trees form because of feeding mites. Eriophyid mites produce a gall that resembles a felt patch and may occur on the upper or lower side of the leaf. The overall health of the tree should not be seriously affected.

Nematode feeding activity can injure roots and allow gall-forming bacteria into the plant. Nematodes can also form galls on carrots, camellia, fig, gardenia, okra, potato, roses, sweet potato, and tomato. Plants can be stunted, yellow, and wilted due to restrictions on the uptake of water and nutrients. Individual nematodes are invisible to the naked eye, but egg masses can be seen as pearly objects. Roots can appear scabby, pimpled, rough, and have knots. Two important prevention methods are to rotate with nematode-resistant crops and to maintain rich organic soil.

Please contact Plant Information Service at (847) 835-0972 or at plantinfo@chicagobotanic.org for additional information.

Praying Mantis “Children” in the Growing Garden

One of our favorite insects at the Chicago Botanic Garden is the praying mantis. So we were very excited to obtain an egg case earlier this spring. We decided to keep it indoors so we could watch it hatch, and then release the newly hatched insects into the Garden.

PHOTO: Preying mantid egg case on a twig. — About 100 praying mantises emerged from this ootheca and were released into the Grunsfeld Children’s Growing Garden.

A praying mantis egg case is called an ootheca (pronouned oh-uh–THEE-kuh). The plural is oothecae (oh-uh-THEE-see). The ootheca was produced by a female praying mantis last fall. She laid her eggs in this foam of protein that hardened around a stick and protected the eggs through the winter. The eggs usually hatch in mid-June to early July. The half-inch-long immature praying mantis nymphs resemble the adult, but they do not have wings.

PHOTO: Hundreds of baby mantids pour out of an egg case. — Colorless praying mantis nymphs emerge from the ootheca all at one time. During their first hour, they darken in color to blend in with their surroundings.

After our praying mantises hatched inside an insect cage, I discovered that a bed of false sunflower plants (Heliopsis helianthoides) in the Grunsfeld Children’s Growing Garden was infested with red aphids. I released the praying mantises, and the hungry babies immediately began to feed.

PHOTO: Mantis nymphs on the head of a Rudbeckia flower covered with aphids. — At first, the praying mantis babies seemed a little bewildered by their new surroundings, but they quickly acclimated.

PHOTO: Mantis nymph on a flower stem eyes aphids—a tasty meal. — This mantis held very still as it eyed its prey.

PHOTO: A row of mantis nymphs on a leaf face a stem covered with red aphids. — These four little mantises lined up and stared at the aphids that would certainly become lunch soon.

It wasn’t exactly aphid carnage—much to the disappointment of our eighth grade Camp CBG helper, Joshua, who assisted me with the release—but the young predators did appear to enjoy their first meal.

PHOTO: Preying mantis on liatris bloom in August. — By the end of August, some of our little friends will be as big as this praying mantis (and just as hungry)!

It may surprise you to know that although it looked like a bad infestation, aphids are not really a big problem for the plants. When they are very abundant, it does not take long for natural predators like praying mantises and ladybugs to find them and move in for a feast. Predatory insects will take care of the problem if you are patient and let nature take its course. If aphids show up in your garden and they bother you, we recommend hosing them off with water rather than using an insecticide, because chances are pretty good that there are beneficial insects on your plants, too. Hosing with a strong jet of water will knock off all the bugs and kill most of the aphids, but it won’t be as devastating to the mantises or other beneficial insects as poison.

We have placed praying mantis oothecae in the Regenstein Fruit & Vegetable Garden and Elizabeth Hubert Malott Japanese Garden, as well as in the Children’s Growing Garden, to ensure that there will be a population of our favorite insect for you to find. Many of them will survive on aphids and other insects they capture and devour on our flowers, and they will grow up over the summer. The next time you visit, stop by and see if you can find them helping our plants remain healthy and less bothered by pests.

Cicadas by the Numbers

Cicadas have been out and singing for a while now. If you live around trees, you may be enjoying their late summer serenade. You also may be finding them on the ground. After they emerge from underground burrows, they molt and enter their adult stage. Then they mate, lay eggs, and die. When you find one, you can examine it to learn more about these big bugs.

Did you know that cicadas have five eyes?

In school we learn that insects have compound eyes, and we use toy bug eye viewers to get a sense of what dragonflies and bees see. But the real picture is a little more complicated. In addition to the pair of compound eyes, many insects, including cicadas, have three simple eyes. They are easy to see on a cicada if you look carefully.

PHOTO: Front "face" view of a cicada, showing 5 eyes. — This cicada’s three simple eyes show up as three spots reflecting the flash from the camera.

The simple eyes are called ocelli, and they are usually arranged in a triangle between the compound eyes, like those in picture of the cicada’s face. Grasshoppers, bees, and praying mantids also have them.

PHOTO: Side view of a cicada. — The Latin name for this cicada is *Tibicen canicularis*. “Canus” is the Latin word for dog. Why do you think he’s called the Dogday cicada?)

Let’s do some cicada math!
If you find a cicada on a tree or the ground, see if you can count:

1 mouth part to drink sap from trees

2 antennae that grow under the eyes and look like whiskers

3 body parts: head, thorax, and abdomen

4 wings, arranged in two pairs

5 eyes, 3 simple + 2 compound

6 legs

Want more cicada by the numbers? Click here to download a Color-by-Number Cicada.

Spring and Summer Camps at the Chicago Botanic Garden

Chicago Botanic Garden camp instructor Aimee Frank discusses the fun and adventures kids experience during Spring Break Camp and Camp CBG. During Spring Break Camp (March 29-April 2) children ages 5-8 discover bulbs, look for birds and other wildlife, and learn about all aspects of nature at the Chicago Botanic Garden. Starting in mid-June, children can attend Camp CBG which provides exciting outdoor learning opportunities for kids ages 2-15.