The Butterfly Center beat: Everything you ever wanted to know about raising Atlas moths

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The Atlas moth (Attacus atlas) is a large moth belonging to the Saturniidae family. Saturniids, familiarly called giant silk moths, include some of the largest species of Lepidoptera (moths and butterflies). Two local species that may be familiar to readers are the polyphemus and luna moths.

Atlas moths are considered the largest moths in the world in terms of total wing surface area. Their wingspans are also among the largest, often reaching over 10 inches. They are strikingly beautiful, with tawny wings punctuated with translucent “windows” bordered by black. Their most distinguishing feature (other than their size) is an extension of their forewings that resembles a snake’s head, thought to be a means of scaring off potential predators.

The forewing of an Atlas moth resembles a snake’s head. ©Erikki Makkonen

The forewing of an Atlas moth resembles a snake’s head. ©Erikki Makkonen

These spectacular moths make superb additions to the Cockrell Butterfly Center. During the day, they spend most of their time motionless, clinging to the side of a tree or other surface. Visitors can thus get up close to intimately study these creatures, and can clearly observe their fat, furry bodies, fuzzy antennae, and teddy bear like expressions.

Close-up of the fuzzy face and feathery antennae of a female Atlas moth (males have larger antennae). © John Horstman

Close-up of the fuzzy face and feathery antennae of a female Atlas moth (males have larger antennae). © John Horstman

Once night falls, the male Atlas moths take flight in search of a female. The search has a sense of urgency, as adult Atlas moths typically live only about one week. This is because the adults do not have fully formed mouth parts and therefore cannot eat; they are sustained only by the fat reserves they built up as a caterpillar. The moths will quickly mate, lay eggs, and die soon after.

One day at the Cockrell Butterfly Center, a male and female emerged from their cocoons around the same time. We took the opportunity to breed and raise this species of moth. The newly emerged male and female were placed in a flight cage in the greenhouses on the top level of the museum parking garage. They paired the very first night they were together. During mating, the moths remained coupled for several hours. Then, over the next three days, the female laid approximately 150 crimson eggs, placing them indiscriminately along the walls and edges of the flight cage.

A mating pair of Atlas moths clinging to the sides of a flight cage. The larger of the two is the female.

A mating pair of Atlas moths clinging to the side of a flight cage. The larger of the two is the female.

Atlas moth larvae are generalists, meaning they will feed on a wide variety of host plants (but not all plants). Hoping to determine which of several possibilities would be the best food for our caterpillars, we searched the literature for recorded host plants.

We chose four that we had available, including Camphor Tree (Cinnamomum camphora), Vitex (Vitex trifolia purpurea), Mahogany Tree (Swietenia mahoganii) and Sweet Potato Vine (Ipomoea batatas). Gathering the eggs, we divided them among four plastic containers lined with moist paper towels and ventilated with tiny holes poked in the lid, each containing a different kind of leaves.

The eggs took 10 days to hatch. The hatchling larvae were covered in pale protuberances and had black heads. After eating their eggshell, the tiny caterpillars began eating the provided foliage. Once the caterpillars were feeding reliably, they were moved to netted cages containing potted plants, so the leaves would be constantly fresh.

The caterpillars hatched on a Friday in September. To track their weekly growth and development, we took a photograph of them each Friday thereafter. It quickly became obvious that the caterpillars on Camphor were thriving: they grew bigger and faster than their siblings on the other plants (the pictures shown below are of larvae fed on Camphor). In each photograph, larvae were placed next to a standard sized Popsicle stick, fondly known as “Size Reference Ralph,” to track their relative growth.

The caterpillars took six weeks from hatching to pupation. They ate voraciously, becoming soft and fleshy to the touch, and were a pale blue-green color. Their backs were covered in a Mohawk of tubercles with a thick, waxy, flaky coating. After six weeks, the caterpillars were almost as long as Size Reference Ralph and were quite pudgy.

The sequential pictures show the dramatic changes in the larvae, followed by the start of silk spinning, and finally a complete cocoon. Once they finished their cocoons, the larvae pupated inside. We then gently moved the dried cocoons to the emergence chamber inside the entomology hall of the Butterfly Center.

Egg to cocoon in Atlas Moths. Pictures were taken one week apart next to Size Reference Ralph. ( Pictures courtesy of Lauren Williamson)

Egg to cocoon in Atlas Moths. Pictures were taken one week apart next to Size Reference Ralph. (Pictures courtesy of Lauren Williamson)

Then we waited. Atlas moths may eclose from their cocoon in as little as three weeks, but can sometimes take several months. To escape from their silken enclosures, they must excrete a substance that dissolves a hole in the silk, allowing them to crawl out. They then cling to their cocoons while their wings expand and dry.

The first Atlas moth of our batch of cocoons emerged on Dec. 17, almost 3 months after hatching from the egg. It was a large female, with a wingspan of just over 10 inches. As you can see, Size Reference Ralph was dwarfed by her!

Our first Atlas Moth to emerge on Dec. 17th 2013. (picture courtesy of Lauren Williamson)

Our first Atlas moth to emerge on Dec. 17, 2013 (picture courtesy of Lauren Williamson).

Know a girl who’s interested in math and science? Come to GEMS (Girls Exploring Math & Science) on Sat., Feb. 8 from 9 a.m. to 1 p.m. The Museum will be filled with hands-on science and math for everyone to experience. Local professionals will be at the Museum to answer questions about their careers in the fields of science, technology, engineering and math.

The event is free with paid admission to the Museum. Click here for $7 admission to all permanent exhibit halls on Sat., Feb. 8.

 

 

Where Have All the Bugs Gone?

It’s that time of year again. The days have gotten shorter and the temperature is slowly dropping. You may have been too busy to notice, but sometime between the shopping and cooking you probably have thought to yourself: I haven’t had to swat away any mosquitoes, or I haven’t been dive-bombed by clumsy June bugs. Where have all the bugs gone? Did they die? Are they hibernating? Well, the answer isn’t quite that simple. Over the last millions of years, insects have learned to employ all sorts of strategies to ride out the winter. While we are putting on thick socks and sweaters, the bugs are right there with us. They are everywhere, right under our noses, literally!

Visitors of the Prayerful Sort
Creative Commons License photo credit:
Clearly Ambiguous

If you’re an insect, you basically have two choices; you can stay or you can leave. An overwhelming amount of insects choose to stay put and deal with the frigid temperatures. One of the best ways to deal with the cold is to suspend your growth and remain as an egg, larva (or nymph), or a pupa. The adults of these insects do die off in the winter, but they are very busy until then. In the late summer and early spring, praying mantidsall around are laying their egg cases in preparation for the winter. They will lay hundreds of eggs, glued together, attached to a stick or leaf, and cover them with a thick layer of foam. After constructing her last egg case, the mother of many will pass away. Through the winter, the egg case will remain safe until it feels the warmth of spring. Then hundreds of tiny mantids will hatch and start the life-cycle over again.

If you are like the June bug, you will spend the winter as a fat grub, lazily feeding on roots all winter deep underground, where it is much warmer. When spring arrives, they form a pupa and emerge as adults in early summer, giving rise to the name June bug. Similarly, dragonfly and mayfly nymphs will remain under the water’s surface where temperatures stay warm enough to sustain them. This is often under a thick layer of ice! There are plenty of mosquito larvae down there to feed them through the long months. Right now in Texas, swallowtail butterflies are forming a chrysalis. The life stage that usually lasts about 2 weeks, will last for 3 months or more. Many of our visitors have a hard time thinking of a chrysalis as a living thing. It doesn’t resemble anything alive at all. When they see them wiggle in response to touch, they are always amazed. The thing that they don’t realize is that aside from not being able to see, they know exactly what’s going on. They can feel the days getting shorter, and the temperature dropping. They won’t make a move to emerge until spring comes!

If an insect is stuck as an adult, the most vulnerable life stage, it gets a little trickier! As long as they can keep their body temperature above 45 degrees Fahrenheit, they will make it. In Texas, this is not a problem, but in the north, they sometimes have to use drastic measures. These insects often find shelter in hollowed out trees, in leaf litter, and under rocks or dead logs.

If this cannot keep the freezing temperatures away they can do something pretty interesting. They can lower the water content in their bodies and replace it with a substance called glycerol. This chemical has several practical uses, but most importantly it lowers the freezing point in their bodies, acting as antifreeze! This is what can make an insect that appears frozen and dead to magically come back to life when thawed. That’s pretty impressive! This, along with going into a hibernation-like state called diapause keeps them alive. One insect that uses this method is the mourning cloak butterfly. This beautiful butterfly is the first to come out of hiding and appear in the spring.

Now if you’re a social insect, you pretty much have it made. Honeybees can store several pounds of honey for food. They don’t even need to leave the hive which is kept warm by the body heat of all the bees. Ant colonies spend all year building up a food supply and stay very deep below the ground. Even some insects that are not social will seek out others to pile on top of for warmth, like ladybugs.

bugs 2
Creative Commons License photo credit: Jef Poskanzer

Butterfly in HDR
Creative Commons License photo credit: chefranden

There are some insects that have opted to take a yearly vacation to sunny Mexico, which would definitely be my choice! The monarch, perhaps the most well known insect in North America makes this amazing journey every year. It’s a mind boggling to think that millions of butterflies fly up to 3000 miles to a few sites that they have never been to or seen before, how do they know how to get there? It is a mystery that keeps us all enchanted by the amazing insect. If you’d like to learn more about the monarch butterfly and their journey, visit the monarch watch website.

Since we live in an area with very mild winters, there are some bugs that we still see all year, including a lot of butterflies. There are a few local monarchs that don’t feel the need to migrate south. Every year we get several calls from people who have spotted a monarch and want to know what will happen to it or if they should help it. The answer we give them is to just let it be, the temperature will probably not drop low enough to kill it and if it does freeze, the butterfly will find shelter. They know how to deal with the cold! So you may enjoy this little break from the bugs buzzing all around us. As for myself, I can’t wait until the spring when all of the bugs are back, happily doing their jobs to keep the world turning! Plus I hate cold weather!

Go buggy! Learn more about insects:
The Sphinx Moth: It’s a Work of Art
Don’t worry, it doesn’t hurt: learn how to pin a butterfly
Do butterflies breed? Your butterfly questions answered