Disease prevention in caterpillars

It’s time to brush up on disease prevention protocols, how to recognize disease, and other disease related information.  The Disease Prevention in Lepidoptera course begins in February.

Nuclear Polyhedrosis Virus NPV killed a Gulf Fritillary caterpillar
Nuclear Polyhedrosis Virus NPV killed a Gulf Fritillary caterpillar

Information in this course applies to every operation from a table top rearing process (hobby and fun level) to large farms rearing thousands of butterflies each week.

Each week for four weeks, you will receive your course material for that week. A course online mailing list will provide means for classroom discussion. An insect pathologist is on stand-by to answer questions, if needed.

Week One covers:
 Breeding Stock
 Egg Production
 Signs and Symptoms of Disease
 Sanitation
 Disinfecting Eggs
 And More

Week Two covers:
 Disease Transmission
 Disease Triggers
 Breeding Stock
 Rearing Environment
 Sanitizing Eggs & Pupae
 Larvae Food
 Disease Disposal
 And More

Week Three covers:
 Specific Diseases
 Disinfecting recipe and directions
 Stain recipe and directions
 Nosema
 How to determine if your stock has these diseases
 Bacteria
 Fungi
 And more

Week Four covers:
 OE
 Parasitoids

If participants do not wish to take the quizzes and exams, no problem. They are required only for a Certificate of Completion.

Your final exam will be emailed to you. All participants who correctly returns the vocabulary words, passes the weekly quizzes, and passes the final exam will be issued certification for completion of the course. Any answer which is incorrect will be returned for correction. A participant cannot fail unless he/she refuses to make corrections when the answers are returned, marked incorrect. The whole purpose is to learn!

Technical assistance was provided, and the course was edited by Ms. Amanda Lawrence and Leellen Solter PhD, Insect Pathologists.

Ms. Lawrence and Dr. Solter are two of the three insect pathologists who graciously agreed to be Consultants for the Association for Butterflies. These two pathologists offered to answer questions which arise at any time during the year. The AFB’s designated spokesperson gathers questions from course participants during the course, sending the questions to one or more of these two professionals when disease discussion reaches a point where additional information is needed.

Week four, focusing on OE, was edited by Dr. Sonia Altizer and Dr. Karen Oberhauser.

Please join us!

Is it right for my yard?

As we plan to add new plants to our gardens, we should think about which plants are best for our area and the species of butterflies in our area of the world.  Just because it is native, attracts butterflies, and produces nectar doesn’t mean it is best for your garden or yard.

Think twice before choosing a new plant.  Do research.  Ask others for advice, people who may know more about the plant that you are considering for your yard.  Some native plants are better for a yard/garden than others.

One of the wild native nectar plants in our area would win your heart when you see the way butterflies flock to it.  It’s a fantastic source of nectar.  Redroot, Lachnanthes caroliniana, is a native plant that grows in wet soil.  There is just one problem: it is extremely aggressive.

Redroot with a Zebra Swallowtail and a couple of Gulf Fritillaries
Redroot with a Zebra Swallowtail and a couple of Gulf Fritillaries

Blooming only in the fall, this plant spreads rapidly and is difficult to eliminate, once it spreads.  It is great for a boggy area if you don’t mind it taking over.

Redroot with at least 7 butterflies, primarily Swallowtails
Redroot with at least 7 butterflies, primarily Swallowtails

When it sends up bloom spikes, it grows a fuzzy white growth at the top, often thought to be the bloom.  Instead, the blooms are yellow flowers that open in the fuzzy white top of the spikes.

Redroot with two Spicebush Swallowtails and one Gulf Fritillary
Redroot with two Spicebush Swallowtails and one Gulf Fritillary

Although native, we advise using extreme caution if you are considering adding this plant to your garden.  A better plant would be one that doesn’t spread so aggressively.  A  plant that blooms all season, spring through fall, is a better choice for a small yard or garden.

Redroot grows in wet soil
Redroot grows in wet soil

Although native plants are wonderful and I have many in my garden/yard, there are some natives that are not good choices for gardens/yards.

This plant would be great for a retaining pond, wet ditch in the country, or other area where it wouldn’t cause issues with its spreading nature.

Think first:

  • Is it right for my yard?
  • Is there a better location for the plant?
  • Should I avoid it all-together?

A good native alternative for a boggy area would be Cardinal Flower, Lobelia cardinalis.  Its red blooms also attract butterflies and provide nectar to many insects.

Cardinal flower and a Cloudless Sulphur butterfly

What are your favorite native nectar plants?

A bubble in the wing?

Someone asked what to do about a bubble in the wing of a butterfly.  First, nothing!  Nothing, that is, until the wings are totally dry.

A freshly emerged Zebra Longwing is leaking hemolyph from its wing.
A freshly emerged Zebra Longwing is leaking hemolyph from its wing. At the same time, it is peeing a bit of meconium.

The bubble is full of hemolymph/blood, the same fluid it used to pump its wings full.  If a wing vein has a leak, a bubble of the fluid will form.  Once the wings dry, the bubble can be popped with no damage.  Even if wings aren’t dry, it usually doesn’t damage the wing but it is best to wait for the wings to totally dry.

A freshly emerged Zebra Longwing is leaking hemolyph from its wing.
A freshly emerged Zebra Longwing is leaking hemolyph from its wing. At the same time, it is peeing a bit of meconium.

Once popped, there will be little flakes of wing that break off, often leaving a hole in the wing. The hole will not damage the butterfly or its ability to fly.

“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.