About Nancy

Nancy is Director of the Cockrell Butterfly Center and curator of entomology. A plant ecologist by training, she specializes in the interaction between insects, especially butterflies, and plants. The tropics are her favorite habitat, and she heads south to Central and South America whenever possible.

Monarchs want YOU to plant milkweed: Butterfly-friendly plants for sale at HMNS

The butterflies need your help! With urbanization, and a host of other factors, monarch butterflies are at risk of not finding places to lay their eggs. So why not help while improving the butterfly traffic through your garden with a butterfly-seducing plant from our biannual plant sale?

Milkweed plants in the genus Asclepias are extremely important for butterflies, especially monarchs. While the blooms provide copious amounts of nectar for many different butterflies, the foliage is an essential part of the monarch butterfly’s life cycle. Milkweeds are the only plant monarch caterpillars will eat. In other words, they can’t live without it!

Native milkweed plants grow along roadsides and in open fields. The butterflies find them by honing in on their volatile chemicals and finally locate the exact plant by “tasting” nearby plants with special receptors called chemoreceptors on their feet. Once a gravid female (one who has mated and is ready to lay eggs) finds a good milkweed plant, she will lay eggs on it — and the miraculous process of metamorphosis has begun!

There are about 100 species of Asclepias in the United States, and over 30 in Texas — but monarchs seem to prefer some of them over others. According to a study by Linda S. Rayor, described in The Monarch Butterfly: Biology and Conservation, when given a choice, monarchs prefer to lay eggs on other species of milkweed over the native species Asclepias tuberosa.

Butterfly - Tropical Milkweed

Besides being a host plant for Monarch larvae, Tropical Milkweed (A. curassavica) is a great nectar source for many butterfly species!

Why? Different Asclepias species contain different cardenolide concentrations (cardenolides are the chemicals in the milkweed leaves that taste bitter). As they eat, the caterpillars store these toxic chemicals in their bodies and thus become distasteful to their predators. A. tuberosa has been found to contain low amounts of cardenolides compared to most other species of milkweed. Although it is unclear how monarchs “know” this, they do not usually use A. tuberosa as a host plant.

Several other native milkweed species, however, are great host plants for the monarch. Asclepias asperula (Antelope Horns), A. viridis (Green Milkweed), A. incarnata (Swamp Milkweed) and A. oenotheroides (Zizotes Milkweed) are some of the more commonly found milkweed plants in our area that monarchs use as host plants.

Unfortunately, most of the native milkweeds are hard to find in plant nurseries. One reason is that their seeds require moist stratification to germinate, and even with this pretreatment, germination can be splotchy. Furthermore, young plants of A. asperula, viridis and oenotheroides take several seasons to establish their thick taproots, and can be hard to transplant.

On the bright side, most of the native milkweeds, except for A. incarnata, are drought tolerant and can handle being mowed. Swamp milkweed obviously likes moist soil. All milkweeds grow best in full sun.

Butterfly - Green Milkweed

Asclepias viridis, Green Milkweed

Most gardeners are familiar with tropical milkweed, or Asclepias curassavica. This plant is commonly available in local plant nurseries and attracts butterflies like a magnet! Its bright orange and gold flowers are irresistible to many butterflies, and the high levels of cardenolides in its foliage make it especially sought out by female monarchs looking for a place to lay their eggs. Although it originates in more tropical climes, it is relatively cold hardy and will usually come back from the base of the plant after a freeze. It is also easy to propagate from seed, and in fact will sometimes seed out (make more of itself) in a garden.

So tropical milkweed seems like the ideal plant. However, one issue with this species is that it is not native to our area and does not exhibit the same characteristics of our native milkweeds, all of which die back to the ground in winter. This perennial habit seems advantageous, but it can be a problem for a couple of reasons. Because it has leaves year-round, it may encourage monarchs to overwinter locally instead of migrating to Mexico. It can serve as a host for a disease that affects monarchs, called Ophryocystis elektroscirrha, or simply O.e. This disease is caused by a protozoan parasite and is spread in the dormant stage of its lifecycle as a tiny spore.

These spores are typically on the abdomen of an infected monarch butterfly and can be spread to her eggs or onto the milkweed plants themselves when a female lays eggs. Then, when the caterpillars hatch out of the eggs, they consume the spores that lie on their empty egg shells or on the leaves around the egg and become infected.

Over a few generations, the parasite load can build up to high enough levels that it impacts the butterfly’s survival. Depending on the severity of the infection, the disease can make the caterpillars look a bit grayish and their stripes not as distinct. When the caterpillars pupate, their chrysalis may look brownish or spotted. The butterfly inside may emerge but have problems, such as an enlarged, gray abdomen and weak, faded wings.

Sometimes they emerge and look healthy, but secretly harbor O.e. spores on their abdomens. Other times they don’t emerge from the chrysalis at all, or get stuck while trying to come out.

So what is my point? I thought we were talking about milkweed plants! ;-) The reason this is important is because O.e. spores persist on the leaves of the tropical milkweed plants, waiting for an unsuspecting caterpillar to munch them up. To break this cycle, we recommend cutting your tropical milkweed plants back after a monarch generation has stripped their leaves, especially in the spring and fall. A simple pruning of the plant’s stems about six inches from the ground will get rid of any remaining spores and will sprout new growth in no time.

Some other closely related plants that monarchs will use as a host are Gomphocarpus physocarpus or “family jewels” milkweed, and a species of Funastrum or twinevine. Gomphocarpus is a lot like A. curassavica in that it doesn’t lose its leaves in the winter so it also needs to be cut back periodically to keep it from spreading O.e.

Butterfly - Funastrum cynanchoidies flower

Funastrum cynanchoidies flower

Funastrum or twinevine is an interesting climbing plant native to south Texas and Mexico. The plant is not very impressive looking until the summer, when it puts on beautiful balls of milkweed-like flowers that are great nectar sources for many kinds of butterfly. Another good thing about it is that when monarch caterpillars have stripped all your milkweed plants of their leaves and are still hungry, they will eat the leaves of Funastrum.

With their habitat dwindling due to urbanization, the use of Round Up ready crops, shrinking right-of-ways due to intensive agricultural practices and other factors, monarch butterflies need all the help they can get. The take-home message today is PLANT MORE MILKWEED! (please)

For milkweed and other awesome butterfly host and nectar plants, come visit us at our biannual Spring Plant Sale on Saturday, April 5th from 9 a.m. until we sell out! We are located on the 7th level of the Museum parking garage. Parking is free if you spend $30 or more!

Come early, the plants go fast!

Exotic edibles & tongue trickery at Cockrell Butterfly Center: Trip out your taste buds Aug. 28!

The tropical vegetation in the Cockrell Butterfly Center features a number of plants with edible fruits. Some, such as coffee, chocolate, pineapple and papaya, are familiar and readily available in local stores.

But most visitors — unless they hail from equatorial climes — are probably  unfamiliar with caimito, jaboticaba, calabash, Barbados cherry or miracle fruit.

One of our favorites is the jaboticaba, a small tree that bears grape-sized fruits in clusters growing directly out of the smooth-barked trunk — very bizarre looking! The tasty pulp inside the rather thick, purplish-black skins is translucent white and juicy, surrounding one to three seeds. Very popular in its native Brazil, jaboticaba fruit is eaten fresh or used in jellies and drinks.

JaboticabaWe get many questions about the calabash tree, which hails from the dry forests of Central America. Strictly speaking, its grapefruit-sized (or larger), green fruits are not edible, although cows and horses may sometimes break open the thick shell to eat the pulp and seeds inside. In El Salvador, the seeds are ground to make the traditional beverage horchata. More often, people dry and hollow out the shell, sometimes carving the surface, and use it as a cup or dipper.

One of our most prolific fruit bearers is the caimito (also called custard apple or star apple) from the West Indies. This tree’s dark green leaves are a shimmering copper on their undersides—the scientific name Chrysophyllum, which means “golden leaf,” is very appropriate! The fruits are the size of large plums and the color of eggplants; inside they have a dense, lavender flesh that is somewhat sweet. The milky sap is quite sticky, so it’s best to eat these with a spoon. (However, we feed most of them to our butterflies, since none of us like the taste much.)

The Barbados cherry has red, cherry-sized fruits that are a little tarter than cherries. Some people grow a miniature form of this tree here in Houston, but the much smaller fruits of this plant are relished only by birds.

"Miracle Fruit"Finally, “miracle fruit,” the color and size of a cranberry, is borne on a shrub from West Africa. One doesn’t eat the fruit for itself, as it is quite insipid, but rather for the amazing transformation of one’s taste perception that results from eating it. Chewing on this berry makes even the sourest lemon taste sweet; it was apparently used in its place of origin to make sour fruits and bitter roots more palatable.

You can experience this interesting sensation yourself if you come to our special “taste-tripping” event on Aug. 28.

WHAT: Adult Hands-On Class — “Taste Bud Tripping with Miracle Fruit”
WHEN: Wednesday, August 28, 6 p.m.
HOW MUCH: Tickets $50, Members $40

The miracle fruit berry from west Africa tricks your taste buds and makes food taste sweeter. Even the most sour and tart foods, such as lemons, are transformed into sweet morsels. Experience the magic of miracle fruit along the dramatically lit trails of the Cockrell Butterfly Center rainforest. After you eat the exotic berry, sample food and drink selected for the delicious impact the miracle fruit has on its taste. Book your taste buds on a trip of a lifetime at HMNS and see why—out of all of the delicious fruits of the Cockrell Butterfly Center flora—the miracle berry fruit is arguably the sweetest.

For tickets call (713) 639-4629 or click here to purchase them online in advance.

Buzz or flutter: Who matters when it comes to pollination? (Hint: It’s everybody.)

In economic terms, bees far outstrip butterflies and moths as pollinators. However, there are some plants that are exclusively pollinated by butterflies — especially some wildflowers and garden ornamentals — and several night-blooming species are specifically pollinated by hawkmoths.

Butterflies and moths are members of the insect order “Lepidoptera” — the scaly-winged insects. In addition to the scales covering adults’ wings, Lepidoptera have unique mouth parts as adults: a long, thin, double-barreled, flexible “straw” that is kept coiled up when not in use and extends to reach deep into flowers to extract nectar. This long proboscis means the plants that butterflies and moths typically pollinate have long, thin floral tubes, making the nectar inaccessible to other pollinators with shorter tongues, such as bees or flies.

courtesy of Wikimedia commons

The technical term for butterfly pollination is “psychophily” — psyche being Greek for butterfly.  Butterfly-pollinated flowers are usually brightly colored (butterflies have the widest-known range of color vision in the animal kingdom), especially in yellows, oranges, reds, pinks, and purples or combinations. Scent is apparently not important for butterflies.  However, the flower structure and position is important.  Butterfly-attracting flowers are often produced in showy terminal clusters of smallish blossoms, each with a floral tube that contains nectar and is easily accessible by the butterfly’s long proboscis.

Smaller flowers are usually pollinated by smaller butterflies, which have relatively shorter probosces; large butterflies such as swallowtails have very long probosces and a longer “reach.” Some familiar examples of “classic” butterfly-pollinated flowers are pentas, lantana (indeed many plants in the verbena family), thistles and coneflowers (and many other members of the sunflower or aster family), and milkweeds, among others.  Milkweeds are especially interesting as their pollen is not powdery but occurs in masses or pollinia, each of which bears a little hook that catches on a butterfly’s leg as it probes among the flower clusters.

A few butterflies (mostly the genus Heliconius in the longwing butterfly family) are known to collect pollen on their proboscis and absorb the amino acids from it.  In general, butterflies do not have the “carrying capacity” for pollen as bees do with their hairy bodies.  However, as they move from flower to flower, enough pollen accumulates on their legs or proboscis to get the job done!

Moth pollination is termed “phalaenophily” (phalaen- meaning moth). A number of moths, including tiger moths, noctuid or owlet moths, and more, visit flowers.  But the best-known pollinators among the moths are the hawkmoths, also known as sphinx moths — the adult form of hornworm caterpillars. These large, powerful fliers are basically the nocturnal equivalent of hummingbirds.  Hawkmoth-pollinated flowers are usually white or pale-colored, making them stand out from the surrounding vegetation at night.  They have long floral tubes to accommodate the very long proboscis of these moths, and many are highly fragrant in the evening, or may only open after dark.  Some examples are moonflower, Brunfelsia, Brugmansia and Datura, night-blooming jasmine, four o’clocks, and evening primrose.

Back to bees:  most of us think “honey bee” when we think of bees, but there are many other bee species, from the familiar bumblebee (not common in our area) to the giant carpenter bees, to tiny sweat bees and colorful leaf cutter bees. These different bee species also have favorite flowers to visit for nectar or pollen (most bees only collect pollen).  For the technophiles, pollination by bees is called “melittophily.”

The wonderful variety of flowers — their shapes, sizes, colors, scents and time of day they bloom, even their placement on a plant — have all evolved to attract a pollinator, often a specific one.  Since plants are rooted in the ground, they depend on things that move, mostly flying things — whether butterfly, moth, bee, fly, hummingbird, bat, or even wind — to transfer their male gametes (in pollen) from flower to flower so that the plants can make more of themselves through forming fruits and seeds.

Next time you are out in your garden, in a field of wildflowers, in a gardening shop, or any place with an abundance of flowers, stop to look more closely at the blooms and think about what pollinator that plant might depend on for its survival.

Are there butterflies in your stomach? Two new types join the Cockrell Butterfly center — one with clear wings

This fall, for the first time we have begun receiving a few Green Birdwing butterflies from one of our suppliers, and are they ever fantastic. The birdwings are very large, tailless swallowtails in the “poison feeder” group — the clan of swallowtails that feeds on poisonous Dutchman’s pipevine plants as caterpillars. Until recently, it wasn’t possible to display birdwings, because the entire group is listed as endangered and it is prohibited to collect them from the wild or sell them, dead or alive. However, a few people are now breeding them in captivity.

The Green Birdwing, Ornithoptera priamus priamus, is from Indonesia and New Guinea (all the birdwings are native to the Indonesian islands, and/or northern Australia). Like peacocks and cardinals among the birds, male Green Birdwings are much more spectacularly colored than the females. Females are larger, but are mostly black, with some white and yellow patches. Males, however, sport glowing, iridescent lines of green and black on their upper side and have similarly shining patches of yellow and green below. Their very heavy abdomens are bright yellow, while the thorax is velvety black with a vivid red patch near the head. Because their abdomen is so large, both males and females seem almost to struggle when flying or hovering at flowers as they feed.

Ornithoptera priamus


We are quite pleased at the relative longevity of these giants — typically swallowtails are rather short-lived, but some of our first batch of Green Birdwings survived for over a month. We also sometimes import another birdwing, Troides rhamadanthus, which is black with a brilliant yellow patch in the hindwing — not quite as spectacular, but still very showy.

The name “birdwing” comes from the size of these butterflies, whose females are the largest butterflies in the world. Alfred Russel Wallace, often cited as the co-discoverer of the theory of evolution by natural selection, was one of the first Europeans to capture and describe these creatures.  Here is his journal entry after first netting a male Ornithoptera croesus (now known as Wallace’s Golden Birdwing):

“The beauty and brilliance of this insect are indescribable, and none but a naturalist can understand the intense excitement I experienced when I at length captured it. On taking it out of my net and opening the glorious wings, my heart began to beat violently, the blood rushed to my head, and I felt much more like fainting than I have done when in apprehension of immediate death. I had a headache the rest of the day, so great was the excitement produced by what will appear to most people a very inadequate cause.”

We hope you will agree with Wallace that these wonderful butterflies are not “an inadequate cause” for excitement, but are a great reason to visit the Cockrell Butterfly Center!

Great Oro

Also new to the Cockrell are Glasswings, or Greta oto. These aptly named creatures are native to Panama to Mexico and even occur in south Texas. Their wings are clear except for the outer rim, hence the name “Glasswing.” Come check them both out in the Butterfly Center!