“How low is too cold for my caterpillars?”

It’s the time of year that the straggler caterpillars, in the more southern US, are outside and may face freezing.  Monarchs, for example, that didn’t go into diapause and migrate, may still be laying eggs if the area hasn’t had a freeze.  But once a freeze is predicted, it’s the time that many of us begin asking that question.  “How low is too cold for my caterpillars?”

Onset of winter
Onset of winter

First, the simple answer.  For Monarchs and those that do not go into diapause as caterpillars, if the lows are above freezing and the day temperatures are above 65-70 F (18.33-21 C), they’ll be fine.  As cold-blooded critters, if temperatures drop too low, they’ll literally freeze.  If temperatures don’t climb high enough in the day, they can’t eat and will either contract disease from their weakness and die or will die from starvation.

Next comes the question of bringing them inside when it is too cold outside.  When they emerge as adults, what if it will be too cold to release them outside?  They can be fed indoors and kept contained.  We recommend Gatorade (not low calorie) as food.  If it isn’t too cold, they can be released.

But the bigger question is this.  Should we bring them in?  That is a personal choice.  There are two basic sides to this question.

1. Some people will save every single one they can save.  They simply do not want one to die.  Period.  They are willing to do whatever it takes to keep them alive.

Feeding Monarch butterflies Gatorade
Feeding Monarch butterflies Gatorade

2. Some people worry that there may have been a genetic glitch that kept them from going into diapause and migrating.  They do not want to pass on that genetic flaw (if there is one) to their offspring to be passed on further, causing this to happen more often.  They will allow nature to make the decision about the caterpillars’ lives.

Frozen Monarch
Frozen (now dead) Monarch with icicles on it

It is a personal choice.  Neither side should judge the other.  Instead, we should all be thankful for all who care about butterflies, whether we agree or not.

From us, we have two words to say to all of you who plant host plants, use less pesticides, teach others, and care about butterflies, whether we agree with your method or not.  Thank you.

Where do parasitoids go in the winter?

It’s bad news for butterflies and moths but good news for parasitoids.  Parasitoids do not die out in the winter, no more than the butterflies and moths that are their hosts.

Tachinid fly infected Monarch caterpillar
Tachinid fly infected Monarch caterpillar

Tachinid flies spend the winter as first instar maggots in their hosts or as pupae inside hosts or in leaves and soil.

Braconid wasp cocoons attached to a Tomato Hornworm moth caterpillar
Braconid wasp cocoons attached to a Tomato Hornworm moth caterpillar

Braconid wasps spend the winter as larvae.

Empty Black Swallowtail chrysalis was parasitized by a ichneuman wasp
Empty Black Swallowtail chrysalis was parasitized by a ichneumon wasp

Ichneumon wasps over winter as adults.

There are many other types of parasitoids, creatures that lay eggs in, on, or near caterpillars.  The wasp larva enters the caterpillar and eats it from the inside out.  Some emerge from the butterfly caterpillar and some emerge from the butterfly chrysalis.  Their numbers thin during the winter, just as butterfly numbers dwindle in the winter. In the spring, both parasitoids and butterfly numbers increase with each generation.

They are a fact of life, playing an important part in the preservation of butterfly and moth species as a whole, even as they kill thousands of caterpillars and chrysalises each year.

Most of us understand their importance in nature but we sing the same refrain. “You will NOT live in MY yard if I can help it!”

Butterfly remembers from caterpillar?

Studies have been conducted to determine whether the adult butterfly remembers from the time it was a caterpillar.   Sure enough, once the studies were concluded, there was scientific fact that they do so. Studies like this are great, providing scientific proof of many things.

We never think of things like this because we assume it would already be known.  After all, the caterpillar is only the young/child form of an adult butterfly.  The ‘brain’ (ganglea) stays the ‘brain’ from caterpillar through chrysalis into the adult.

False foxglove with tiny leaves is a Buckeye butterfly host plant
False foxglove with tiny leaves is a Buckeye butterfly host plant

We had been raising plantain (Plantago lanceolata) for a couple of years before we started to raise Buckeye butterflies.  Because their host plant that they use in the fall has tiny leaves that dehydrate almost immediately, even when placed in water, we were desperate to find another host plant.  Reading a bit in a couple of books, we read that they also host on the same plant we were growing as an herb at our herb nursery.  We placed few large full-leafed plants with caterpillars.  The next morning, the leaves were completely devoured, down to and below the soil level.  We released quite a few of the adult butterflies when they emerged.  Before long, our plantain, growing in pots for customers, were tiny instead of as large as they had been.  They were covered in Buckeye caterpillars.  Although thousands of Buckeyes migrate through every spring and fall, they had never laid eggs on our plantain before we raised caterpillars on it.  Once we fed caterpillars plantain and released the resulting adults, they laid eggs all over the plantain.  After the initial surprise to see the plants, which had never been eaten, suddenly covered in hundreds of caterpillars, we realized it made perfect sense.  The butterfly with wings is nothing more than the caterpillar all ‘grown up’.

Buckeye butterfly caterpillar eating ribgrass plantain
Buckeye butterfly caterpillar eating ribgrass plantain

We learned that raising caterpillars on a less-favored yet totally legitimate host plant is a good way to start a generation that will, for the most part, prefer that plant when they lay eggs.

There are so many topics that are still waiting to be studied in proper scientific studies.  Done properly, any of us could do these studies and write up a paper on our experiments and results.

What have you learned that you later realized was new information to butterfly and moth enthusiasts, citizen scientists, and/or lepidopterists?

 

Freezing temperatures and butterflies

Now that much of the US has already experienced freezing temperatures, butterflies and moths in those areas are set for the winter. Those that overwinter have gone into diapause. Those that migrate south have migrated. Those that will die in the cold have done so.

So where are they? Let’s look!

Some species, such as Mourning Cloaks and Question Marks stay where they are (as adult butterflies) during the winter. Hiding in cracks and crevices in wood, they come out only on the warmest days, if at all.

Question Mark butterfly
Question Mark butterfly
Mourning Cloak butterfly
Mourning Cloak butterfly

Some are young caterpillars, simply tucked away in sewed-together leaves.  Having produced sorbitol and glycerol in their hemolymph/blood, they can withstand freezing temperatures for days to months without a break.

 

A Viceroy caterpillar hides in a rolled leaf for the winter.
A Viceroy caterpillar hides in a rolled leaf for the winter. The caterpillar is totally hidden.
Tawny Emperor caterpillars hide inside leaves during the winter.
Tawny Emperor caterpillars hide inside leaves during the winter.

Some species, such as the Striped Hairstreak, spend the winter in their eggs.  In the spring, the eggs hatch and the young caterpillar begins eating fresh tender leaves.

Striped Hairstreak butterflies spend the winter as eggs. All other stages die before winter or in the cold that winter brings.
Striped Hairstreak butterflies spend the winter as eggs. All other stages die before winter or in the cold that winter brings.

Swallowtails and a few other species spend the winter in chrysalis.  Whether in a milder winter in Florida or months of ice and snow in Canada and the northern US, the chrysalis can survive sub-zero temperatures.  In the spring, the adult butterfly emerges, mates, and begins laying eggs on fresh tender spring leaves.

 

Eastern Tiger Swallowtail chrysalis on a stem.

Gulf Fritillary butterflies fly south and spend the winter in warmer areas, where day temperatures stay above 60 degrees.
Gulf Fritillary butterflies fly south and spend the winter in warmer areas, where day temperatures stay above 60 degrees.

 

Monarch butterflies in Mexico, where they spend the winter in the mountains where temperature are cool.
Monarch butterflies in Mexico, where they spend the winter in the mountains where temperature are cool but do not stay below freezing.

So while we go about our business in cold temperatures, wearing heavy coats and turning on heaters, butterflies have either flown south or are waiting out the cold, patiently waiting until spring when longer days and warmer temperatures trigger them to come out of diapause and begin active living again.

Why raise butterflies?

Why should we raise butterflies, Monarch and other species?

We can save them from predation.  Wasps, birds, spiders, predatory stink and assassin bugs, ants, and many other critters kill them, egg through adult.  Predation, from egg through chrysalis, isn’t about survival of the fittest.  Eggs, caterpillars, and chrysalises cannot run away and escape.  This is about saving many that otherwise would die.

We can save them from disease.  Disease is rampant in nature.  From simple bacterial diseases to the horrific viruses, such as Nuclear Polyhedrosis Virus, when we bring in eggs and caterpillars we can prevent many of them from becoming diseased.  Raising butterflies in a clean environment with clean sanitary practices saves many from death.

Gulf Fritillary caterpillar dead from NPV
Gulf Fritillary, dead from NPV

We can save them from parasites like OE, a protozoa that parasites Monarch and Queen butterflies as well as other butterfly species that host on milkweed.  By bringing in eggs and disinfecting them as well as disinfecting the plants we feed them, OE can be avoided.

OE spores on a wild Queen butterfly
OE spores from a wild Queen butterfly

We can save them from parasitoids.  Tachinid flies, chalcid wasps, and other parasitoids lay eggs in or on caterpillars or soft chrysalises.  By bringing them in before they are infected, we can protect them.

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NOTE: Disease, parasites, parasitoids, and predation are tools that nature uses to keep the species, as a whole, alive.  You can learn more about nature and death by clicking on this sentence.

When we raise caterpillars and others see what we do, it ignites a passion in others.  This passion leads others to become aware of butterflies and their enemies as well as their needs.

A private butterfly garden with dozens of species of host plants as well as dozens of species of nectar plants
A private butterfly garden with dozens of species of host plants as well as dozens of species of nectar plants

It teaches our children to respect and protect butterflies and our environment.  As we raise caterpillars, our children learn from us.  They learn the importance of building and protecting habitat, not just for butterflies, but also for other pollinators.

Jonathan discovers a Gulf Fritillary caterpillar in the garden
Jonathan discovers a Gulf Fritillary caterpillar in the garden

It teaches us the dangers of pesticides.  Many of us grew up in an era when pesticides were encouraged, far beyond the amount of encouragement today.   Pesticides were considered crop-savers.  Once we start raising butterflies and see the effect of pesticide, first hand, we re-evaluate our use of pesticides.  We either limit the types of pesticides we use or we totally eliminate the use of pesticides.  We begin to educate others, including nurseries, and (as a result) fewer pesticides are used on plants.

A crop duster returns from spraying crops with pesticide
A crop duster returns from spraying crops with pesticide

People share butterfly host and nectar plant seeds and plants.  Many enthusiasts give away seed, some asking for a self-addressed-stamped-envelope.  This adds to the number of pesticide-free butterfly plants that are grown for butterflies.

envelopes stuffed with (free) butterfly host and nectar plant seed
Envelopes stuffed with (free) butterfly host and nectar plant seed

It is a passion that is fun.  Because we clearly enjoy it, others become interested in what we do.  We are able to teach others about butterflies.  As a result, butterfly numbers increase.  More habitat is planted.  More people use fewer pesticides.  Even the choice of which government official receives our vote can be affected by whether or not they choose to protect our environment.

Why raise butterflies?  There are numerous reasons, all good for butterflies and nature in general.

 

Pupating lying down?

Sometimes a caterpillar will fall after it attaches.  What to do?  Some species will pupate fine laying down.  Some of those, such as Monarch, must hang to finish forming or they will form with one side flat.  Others, like swallowtails, do fine if they are left laying flat on a soft surface after they pupate.

Gulf Fritillary pupating on a coffee filter
Gulf Fritillary pupating on a coffee filter

When a Gulf Fritillary container built up too much moisture and several caterpillars fell after they had attached, I laid them on a coffee filter and continued feeding other caterpillars.  I decided to watch and see what happened.  As they pupated, I used old silk and attached them to the old silk.  This works if they are freshly pupated.  I left others laying on the coffee filter.  The next day most had pupated and hardened without problem.  Although there was a greater curve to the abdomen than normal, they emerged and flew without problem.

This method works well for swallowtails.  When one has attached in the wrong place or has been found laying down before pupation, they can be laid on a coffee filter or other soft paper and they will (almost always) pupate and harden without problems.

Now, when I don’t have time to wait for them to pupate so I can reattach them, I leave them laying down.

Note: if they are left on a hard surface, such as a counter top or desk, the soft chrysalis often adheres to the surface as it hardens.  When the chrysalis is moved, it either leaves part of itself attached to the surface or has a shiny deformed side.  We always leave them on a soft surface, such a a paper towel, tissue, or coffee filter.

WHEN do we know a host plant is safe (pesticide-free) to feed to caterpillars? 

Pesticide is a fearful thing when we’re raising butterflies and moths.

spintor

When we buy a plant or think our plants may have been treated with pesticides, we test the plant on one or two caterpillars before feeding it to all the caterpillars we are raising.  But the question is WHEN do we know a plant is safe to feed to caterpillars?  If the caterpillars are alive the next day, is the plant OK?

insecticide.bright.greenlorena.popelka.6

The answer is a simple and resounding NO.  Some pesticides will kill immediately.  Others take a day or two.  Some take three days (such as Bt).  Others will slowly kill them, by interfering with their mandibles and how much they can eat (lack of nutrition).  Yet others won’t affect them at all until they begin to pupate and won’t be able to finish the pupation process.

malathionandorganicidetreatedmilkweed6

If caterpillars are fed some pesticides just before they pupate, they will emerge fine, inflate and dry their wings, and begin to fly before falling to the ground, quivering and dying with their wings folded downward over their legs.

The only fully correct answer is that a caterpillar should be fed the plant and it considered unsafe until it emerges and lives a day as an adult.  BUT …

In most cases, after a caterpillar that has been eating the plant has successfully and fully pupated, it is safe.  

That isn’t the answer we hoped for but it is the answer we want, the one that will help prevent more deaths.

cropduster6