Why are freezing temperatures good for butterflies?

We dread winter when we think of butterflies. It’s cold. Butterflies aren’t flying. We may go months without butterflies (depending on where we live). So why should we be glad for the freezes that kill back butterfly host and nectar plants? Why should we grin when we see our frozen plants?

Ice-covered passionvine

When most of these plants are frozen, they die back to the stems or to the ground. The leaves are killed and fall off the plants. THAT is the reason to be happy. The leaves are killed and fall off the plants. If that doesn’t make sense, read on!

Frozen pipevine leaves

Out of 100 eggs laid by a butterfly, only about 2 live to become adults. Nature kills the other 98. This is the way that nature is able to keep the species alive. If there were too many butterflies, they’d eat all the host plants and starve, eventually causing the species to become extinct. If you’d like to see the numbers, check out this page.

Various diseases are one of the many methods that nature uses to kill caterpillars and chrysalises. Besides diseases, nature also supplies parasites, predators, parasitoids, and a few other methods to kill eggs, caterpillars, and chrysalises.

Freezing temperatures kill most disease pathogens and most OE spores. Viruses survive freezing temperatures, though. When leaves are killed by a freeze, they eventually fall off the plant and begin decaying. As the decaying leaf washes into the soil, pathogens also wash deep into the soil, ensuring that caterpillars cannot become infected and become diseased.

One of the worst diseases to affect caterpillars is Nuclear Polyhedrosis Virus – NPV. An infected caterpillar, once it is close to dying, will crawl to the top of its plant. There, it waits. It slowly turns to liquid as it dies. The dead caterpillar begins dripping its liquid contents. This liquid falls onto and splashes all over the plant/vine. As it rains or we water our plants, the pathogens are washed off the contaminated leaves and splashed over more leaves. Once another caterpillar eats the virus pathogens, it contracts the disease and dies.

NPV killed this Gulf Fritillary caterpillar. Its insides turned to pure liquid, containing about a billion virus pathogens. The liquid drips out of the dead caterpillar, spreading the virus pathogens over the host plant.

Winter is a time of cleansing. As our gardens grow back in the spring, most of the disease pathogens have been killed or are being washed into the ground. The fresh leaves that caterpillars eat will be healthy and clean. Soon our gardens will again be full of caterpillars and adult butterflies.

In the winter …

Here it is, the middle of winter in the northern half of the world. People aren’t seeing butterflies unless they live below the freeze line, areas equal in the longitude of the central and southern part of Florida, and below. Because butterflies are cold-blooded, they cannot be active when temperatures are too low. If they are caught too far north, they will die unless they are a species that goes into diapause as adults (overwinters as adult butterflies) in the north.

Mourning Cloak butterfly

So what do we do in the winter that pertains to butterflies?

  1. Disinfect rearing containers. No matter if they are made of glass, plastic, mesh, screen, wire, or any other material, they should be disinfected after each batch of caterpillars before they are used again. Nature has many butterfly diseases that contaminate rearing containers.
  2. Repair rearing containers. Mesh, cloth, screen, and other materials sometimes become torn or damaged. Mice, rats, and other predators will eat holes in containers to eat the contents. They can be repaired with glue, wire, thread, or other items. When a mesh habitat is damaged beyond repair, save the undamaged mesh (cut out the sides) for future repairs.
  3. Order more rearing containers if you need them (or even if you simply want more). You need enough containers to be able to disinfect them between batches of caterpillars. Remember that it is best to never emerge adult Monarch or Queen butterflies in the same container where there are caterpillars.
  4. Plan your new spring butterfly plantings. Remember, don’t limit your butterfly plants to just one area. Plant them here and there throughout your yard. Make your land a butterfly habitat, copying nature. Nature plants butterfly plants between other plants. This provides some protection for butterflies (egg through adult).
  5. Read books about butterflies and their plants. Your local library will have butterfly books you can check out and read.
  6. Join butterfly and gardening clubs, either in person or online. There are many Facebook groups that focus on butterflies. Share your experiences and photos. Ask questions. If your focus is Monarchs, we encourage you to join The Beautiful Monarch. There are too many wonderful butterfly pages for us to begin to list the best.
  7. Preorder plants, supplies, and kits. Sometimes supplies are limited and pre-ordering ensures that your order is filled before later orders.
  8. Organize your butterfly related photos. Most of us take hundreds of photos of butterflies, our gardens, and other butterfly related items. It’s a good time to organize them on your computer to make it easier to find specific photos later. Remember, take photos of everything, including the bad things. If you are raising caterpillars and some get sick and die, sharing these photos with knowledgeable people who care can sometimes answer the question of “what happened?”
  9. What else butterfly related do you recommend for winter months? Please share your thoughts with us in the comment section of this blog.

Trogus pennator

Trogus wasps are parasitoids that lay eggs in swallowtail caterpillars. There are four different Trogus species in the Eastern US and Canada.

Trogus pennator wasp

Trogus pennator wasps resemble the common red wasp that we know well. Most of us avoid the red wasp. Their stings are painful. The parasitoid wasp, Trogus pennator, doesn’t sting like red wasps sting people. The body is red/orange and the wings are black with a blue sheen. The abdomen is clearly segmented and flatter than a red wasp abdomen. It’s a beautiful wasp.

The adult wasp seeks out caterpillars and lays a single egg in the caterpillar. At the proper time, the egg hatches, and the wasp larva eats the inside of the developing butterfly. This kills the chrysalis.

Once the wasp becomes an adult, it eats a large hole in the side of the chrysalis and emerges, seeking a mate and food. The adult wasp mates and the female is now ready to lay her eggs in more swallowtail caterpillars.

Texas Butterflies and Their Plants

Butterfly species vary from area to area, state to state, and region to region. Plants chosen for a butterfly garden in Florida many not be the best plants for a garden in Texas.

In Texas, these are some of the plants that would be great in a butterfly garden. Some butterfly species in north Texas are not found in south Texas and vice versa.


Pawpaw (Asimina species) for Zebra Swallowtail [eastern edge of Texas only]

Fennel, parsley, dill, carrot tops, Queen Anne’s lace, and other plants in the fennel family for Black Swallowtail [all of Texas]

Hop tree, citrus, prickly ash, rue, and related plants in the citrus family for Giant Swallowtail [all of Texas]

Black cherry (prunus serotina), choke cherry (Prunus virginiana), sweet bay (Magnolia virginiana), basswood, tulip tree (Liriodendron), hop tree, birch, ash, cottonwood, and willow for Eastern Tiger Swallowtail [the eastern half of Texas only]

Spicebush, sassafras,  red bay (Persea borbonia), swamp bay (Persea sp.), silk bay (Persea sp.), for Palamedes Swallowtail [very eastern edge of Texas] and Spicebush Swallowtail [eastern edge of Texas)

Certain Pipevine species for Pipevine Swallowtail [all of Texas]

Certain Pipevine species for Gold Rim (also called Polydamas) Swallowtail [Gulf Coast area of Texas]

Alfalfa, white clover, and other plants in the pea family (Fabaceae) for Orange Sulphur [all of Texas]

Plants in the Senna/Cassia family for the Cloudless Sulphur and Sleepy Orange [all of Texas]

Cabbage, radish, spider flower (Cleome sp), peppergrass (Lepidium species), nasturtium, beach cabbage, clammyweed, and other plants in the mustard family for the Great Southern White [southwest half of Texas], Checkered White [all of Texas], and Cabbage White [all of Texas]

Plumbago for Cassius Blue [San Antonio and further south]

Hackberry for American Snout [all of Texas], Tawny Emperor [all of Texas], Hackberry Emperor [all of Texas], Question Mark (all of Texas0 and Mourning Cloak [all except the most southern tip of Texas]

Milkweed (Asclepias species) for Monarch [all of Texas] and Queen [all of Texas]

Black cherry and choke cherry (Prunus species), deerberry, birch, willow, and shadbush for Red-spotted Purple [eastern and southern halves of Texas]

Willow, poplar, and cottonwood for Viceroy [all of Texas]

Specific passion vine species for Gulf Fritillary [all of Texas], Variegated Fritillary [all of Texas], and Julia [southeastern third of Texas] (Passion vine available from Shady Oak are located here)

Specific passion vine species planted in the shade for Zebra Heliconian [all except the northern half of the middle of Texas] (Passion vine available from Shady Oak are located here)

Frogfruit (Lippia species), water hyssop (Bacopa species), and ruellia species for the White Peacock [southwest half of Texas]

Cudweed (Gnaphalium sp), pearly everlasting (Anaphalis margaritacea), plantain (plantago sp), frog fruit (Lippia sp) for the American Lady [all of Texas]

Hollyhock, mallow, pearly everlasting, thistles (Asteraceae sp), plantain (Plantago sp), and many more for the Painted Lady [all of Texas]

False nettle (Boehmeria cylindrica) or nettle (Urtica sp) for the Question Mark [all of Texas], Red Admiral [all of Texas], and Eastern Comma [eastern third of Texas]

Snapdragon, plantain (Plantago sp), twin flower, wild petunia, some plants in the Ruellia family, and toadflax (Linaria) for Common Buckeye [all of Texas]

Leafy prairie clover for Southern Dogface [all of Texas], Sleepy Orange [all of Texas], Cloudless Sulphur [all of Texas]

Some plants in the Scrubby plants in the acanthus family (Acanthaceae) for the Crimson Patch [all of Texas]

Sunflower for Bordered Patch [all of Texas]


Sweet gum for Luna moth

Texas sage (also called Ceniza) (Leucophyllum frutescens), Mexican jumping bean, ash, and ocotillo (Fouquieria splendens) for the Calleta silkmoth [extreme southern part of Texas]

Oak, maple, willow, and birch for the Polyphemus silkmoth [all except the northern part of Texas]

Pine, maple, oak, box elder, sweet gum, and sassafras for the Imperial moth [eastern half of Texas]

Willow, black cherry, box elder, sugar maple, plums, apple, alder, birch, and dogwoods for Cecropia silkmoth [eastern half of Texas)

What is a cocoon?

Silk moth cocoons

What is a cocoon? A cocoon is the silk ‘sleeping bag’ some species of moths make before they pupate. A caterpillar creates the silken cocoon with a silk gland/spinneret that is located under its mouth. Butterfly caterpillars do not make cocoons. (Some people consider the nest that a few species of butterflies make before pupating – a cocoon.)

Polyphemus moth cocoon

Not all species of moths make cocoons. Some pupate in leaf litter and some pupate under the soil. Some make a leaf nest, not a ‘cocoon’ as most of us think of a cocoon.

A Tersa Sphinx Moth pupa, dug up from the top layer of soil near a pentas plant

All butterflies and moths go through four stages. Ova (egg), larva (caterpillar), pupa (pupa or chrysalis), and imago (adult. A moth pupa is called a pupa (singular = pupa and plural = pupae). A butterfly pupa is correctly called either a pupa or a chrysalis. A butterfly pupa/chrysalis is not called a cocoon. A moth pupa is not called a chrysalis.

Gulf Fritillary butterfly chrysalis

Cocoons that are used to make silk material contain about four thousand feet of one long silk strand.

It does not harm the pupa to cut the cocoon open and remove it, as long as the pupa is protected from predators and dehydration. If it is removed, it should be placed in a container where it can emerge and climb high to expand its wings.

A freshly pupated silk moth pupa was removed from its cocoon

Inside the cocoon is the moth pupa. Once the cocoon is finished, the caterpillar takes about three days to pupate. Changing from moth caterpillar to pupa is a longer process than changing from a butterfly caterpillar to chrysalis. Butterflies usually pupate within 24 hours.

A Cecropia moth caterpillar makes its cocoon

Butterflies and moths both pupate from caterpillar to pupa. A butterfly pupa is often called a chrysalis.

Red Admiral butterfly

Red Admiral Butterfly
Red Admiral Butterfly – Vanessa atalanta Red Admiral Butterflies are found during the winter months in Florida. They prefer cooler weather, laying eggs on Pellitory and False Nettle around our area. They also lay on stinging nettles around the United States. We definitely prefer False Nettle to the stinging nettles!

In the above image, you can see where Red Admiral Butterfly  caterpillars have created a ‘tent’ out of host plant leaves. Look for these tents while searching for caterpillars in the wild.

At the farm, we feed them a mixture of False Nettle and Pellitory, depending on the time of year and what is most readily available. Pellitory only grows in the cooler months for us, seeds germinating and sprouting in the fall, dying back once the weather gets hot again in late spring. During the warmer months we use False Nettle.Read below to follow us as we care for our Red Admiral Butterfly caterpillars in the lab here at Shady Oak Butterfly Farm.
We start with eggs laid by our breeder butterflies. This image is of Red Admiral eggs on False Nettle. In the wild, you will not find a large number of eggs on a single plant, this is only the result of several adult females in an enclosure with one host plant provided.

We keep the plant in a mesh habitat and water it daily while waiting for the eggs to hatch. False Nettle requires a great deal of water, and will even grow in standing water along rivers and in ditches in the wild.

It is easy to tell when the eggs have hatched! The caterpillars will eat quickly and the leaves become skeletonized.
The small black caterpillars will soon be seen sitting on the leaves. These caterpillars are around 1 week old. When first hatched they are very difficult to see due to their tiny size. At this point, we transfer the caterpillars to cups.

Here you see a handful of Pellitory we have gathered to feed the caterpillars. They will not need many leaves at first, but as they grow their host plant needs grow with them!

Here is a tote of cups, each holding one Red Admiral caterpillar. You can see that most have eaten all the food provided from previous day. The cups on the bottom left have already pupated and the chrysalises were left to harden overnight before removing them from the cups.

The cup on the left in this image still has green leaves left, which is a clue to me that the caterpillar may be done eating during the larval stage and is ready to pupate!

Another image of the cup from the side. Plenty of leaves left, but no sign of a caterpillar on the lid – I will need to open the cup to investigate further.

Still no sign of the caterpillar…

Ah-hah! Found him. Red Admirals love to form their chrysalises inside a small ‘tent’ of host plant material. We always have to keep that in mind while removing old leaves from cups and habitats.

The chrysalis has hardened and is ready to be removed and taken into our pupae room. We do not keep chrysalises in the same room as caterpillars.

Here are a few more chrysalises that were removed and taken to another room. This batch will be used as breeders. The next batch of caterpillars will be ready to ship out in a few weeks. 

Once the butterfly has fully formed and is ready to emerge from the chrysalis, you will see the wings through the chrysalis cuticle. This butterfly will emerge within the next 24 hours. We will have Red Admiral Butterfly caterpillars available in a few weeks, reserve yours today! They are available for pre-order on this page. Are you interested in adding Red Admiral Butterfly Host Plants to your butterfly garden? False Nettle – Bohemeria cylindrica and Pellitory – Parietaria floridana 

What killed my caterpillars?

When we’re raising caterpillars in our homes, we are fighting nature. Nature has a goal of killing 98% of them before they become adult butterflies. The odds are stacked against us before we even bring a caterpillar from our garden to our home.

Nature uses disease as one method to keep a butterfly species alive while killing most caterpillars.

Gulf Fritillary caterpillar died from Nuclear Polyhedrosis Virus (NPV)

NPV – Nuclear Polyhedrosis Virus – is one of the worst diseases. One caterpillar can have a billion virus particles in its body. The virus causes caterpillars to crawl upward before they die. The caterpillar or chrysalis turns to liquid and the virus particles drip and splash, covering a large area as it rains or we water or gardens. Another caterpillar needs only to eat a leaf with invisible virus particles on it and it will soon die of the disease too.

Monarch with anal prolapse
Gulf Fritillary with anal prolapse

Anal prolapse may happen naturally. It can also be caused by exposure to some pesticides. The digestive tract begins to come out of the caterpillar’s anus. When this happens, the caterpillar will die.

A Monarch chrysalis failed to finish forming and sealing properly

It is natural for a chrysalis to be deformed or fail to finish forming properly. It shouldn’t happen often. If it happens to more than a couple at a time, chances are that they have been exposed to a pesticide. Some pesticides cause failure to pupate.

Monarch caterpillars quit eating due to Bt (Bacillus thuringiensis) bacteria ingestion

Bt is a natural soil-dwelling bacteria. When caterpillars take a bite of food that includes Bt, its gut lining begins to break down and it stops eating. Three days later, the caterpillars die. One of the first signs of Bt ingestion is what you see in the photo above. Caterpillars had been given fresh food 18 hours earlier and didn’t eat more than a couple of bites

Dehydrated Red Admiral and Julia chrysalises

Chrysalises can dehydrate if they are in a dry area. In nature, they usually have plenty of humidity from the plants around it. In captivity, they sometimes die from lack of humidity. The butterflies fully form yet die before emerging. The tell-tell sign is that chrysalises are light as a cotton ball and when broken open, they are dry inside.

A deadly fungus kills a moth caterpillar

Fungi kills caterpillars, chrysalises, and adult moths and butterflies. When you touch caterpillars or their food, always wash well first. It is easy to track/carry spores with you as you touch a plant in nature with the spores before picking food for your caterpillars.

Bright green spit/vomit from pesticide exposure

Caterpillars that are exposed to certain pesticides will spit or vomit green liquid. Some spit green as a defensive mechanism. In time, you’ll learn which naturally spit green when touched and which are reacting to pesticide exposure. Spit/vomit stays green. Hemolymph (like blood) that drips from a caterpillar or chrysalis will turn black or gray within five minutes.

Monarch caterpillars abnormally colored

One of the signs of disease is abnormal coloration of caterpillars. Sometimes the abnormal color is natural, from cooler weather or genetics, but sometimes it is from disease.

Bacteria can cause abnormal coloration of pupae, such as with these three Monarch pupae

There are many signs that you can see from bacterial infection. An abnormal color of caterpillars or chrysalises can be caused by bacterial infection.

Improper molt of a Monarch caterpillar

Caterpillars should do a complete molt, their cuticles coming off in one piece. When a molt looks like this, it is a sign of other problems, disease or even a too-dry environment.

OE infected Monarch butterfly

OE (Ophryocystis elektroscirrha) is a protozoan parasite that infects Monarch, Queen, and other species that host on milkweed. In the photo above, we see the discolored abdomen and crumpled wings, classic signs of OE. The adult butterfly is often sticky with a darker than normal abdomen. Quite often, in the worst cases, adult butterflies cannot get out of their chrysalis shells.

What can you do? Use caution. Stay clean. Clean the rearing area well. Disinfect rearing containers between every generation of caterpillars. Check every milkweed-eating butterfly for OE spores. Avoid pesticides. When purchasing host plants, ask if they have been treated for plant pests and be aware that the retail nursery may not have been told if the wholesale nursery has treated the plants earlier. Remember that organic pesticides are as deadly as inorganic pesticides – both are created to kill plant pests.

Jonathan found a Gulf Fritillary caterpillar in the garden

Be aware that when you bring in a caterpillar, it may already have had a death sentence and you can do nothing about it. Focus on the butterflies and moths that you raise successfully.

Thank you all for what YOU do for butterflies!

Orientation of Attaching to Pupate

Why do caterpillars tend to attach with their legs toward the light? Or do they?

We noticed that most of the Monarch chrysalises in our lab were oriented with their legs to the light. We did a test to see if this was right. Was it our imagination? We selected four containers with Monarch caterpillars and placed them in specific spots in the room, on opposite walls, to determine whether this was so. Each container was marked and placed in the exact same spot, level, and position each day.

Containers of Monarch butterfly caterpillars in the lab, fed daily, removed when they became chrysalises, and were then shipped to exhibits throughout the US.

In each container, Monarch caterpillars were housed and fed fresh milkweed daily.

Monarch caterpillars and chrysalises in the lab.

Out of 30 chrysalises in each container, only two or three attached with their backs to the light. Most were angled with their legs more to the light than to the back.

Nearly all the Monarch chrysalises had pupated with their legs toward the light.

More studies need to be done by others to see if this proves true in all areas. Our one study does not make a definitive scientific conclusion other than, in our lab, they pupated with that orientation.

If this position is an advantage, why? We believe that pupating with their legs toward a solid object, as they pupate on in nature at times, can cause life-threatening damage to the finished chrysalis. When attaching to a fence, side of a house, or other solid object, pupation direction may be a life-death instinct. If they attach on or to a flat object, that side will be darker. If the back of the abdomen is flattened by a stem or wall, the adult butterfly will look and function normal. If the leg/antennae/proboscis area is flattened, it often leads to failure to pupate properly which can cause death or disfigurement that leads to death.

If it is an advantage, those that had an instinct to pupate with their backs to the light would be less apt to survive. The number that die would be minimal, perhaps not enough to make a difference. Was our experience a coincidence or is this the normal ratio of angle to the light that happens all over in the Monarch world?

Fatal damage to the leg side
of a Monarch chrysalis

Please do your own studies. Do they pupate the same way in your house? Do you see more damage with those that pupate with their backs to the light? When we all observe what happens in our own caterpillar rearing environments, we all learn.

Spotting late Monarchs?

Why are people reporting so many Monarch (and other species) of butterflies later in the year than normally reported? There are several simple reasons.

  1. More people are noticing butterflies, especially Monarch butterflies. The internet has increased the number of people who recognize Monarch butterflies. More people (than in the past) are aware of the dates they should normally be absent in an area. They record and share the dates that they spot Monarch butterflies in their area. In the past, when people would see the exact same species on the exact same place and on the exact same date they didn’t report it. It meant nothing to them.
  2. More people are raising caterpillars indoors. This protects them from nature’s enemies, including cold temperatures. Many of the butterflies spotted were raised indoors. If they had been left outdoors, low temperatures would have killed them. There are more late-season butterflies because people save them from the weather.
  3. Artificial lighting (along with artificially raised temperatures) in communities and around houses often give a false sense of the time of year to caterpillars under the lights. This can prevent some from going into diapause and/or migrating.
Monarchs overwintering at Norma Gibbs Butterfly Park in Huntington, CA
Monarchs overwintering at Norma Gibbs Butterfly Park in Huntington, CA

Late season butterflies aren’t a reason to panic. Nature will take care of them. If they are where it will freeze, they will die unless they are a species that survives freezing temperatures, such as Mourning Cloak butterflies.

Mourning Cloak butterfly

Extra reports of late-season butterflies are a sign of good things: that people are noticing them and reporting them. When more people are aware of butterflies and their natural lives/life-cycles/timing, they are less apt to use insecticides in their gardens. They are more apt to plant butterfly host and nectar plants.

“Which of these is a butterfly?”

Monarch Life Cycle

The answer, of course, it ALL of them.

It helps to know which stage is a butterfly. When I do presentations for children or students, I always ask that question.

We have a BUTTERFLY egg (undeveloped butterfly), a BUTTERFLY child (young butterfly – caterpillar), a BUTTERFLY teenager (chrysalis – a maturing butterfly – going through sexual maturity), and an adult BUTTERFLY.

They are all the same organism, same critter, just one that is maturing. The caterpillar is not a different creature. It simply has a different appearance. The chrysalis is not a different creature. It simply has a different appearance.

A few years ago, a woman called our office, asking how she can kill the ‘worms’ eating her passion vine without harming the butterflies. She was unable to grasp the fact that the ‘worms’ (caterpillars) were butterflies in child form. Once people grasp that important fact, they begin to use less pesticides and plant more host plants.