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.

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

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.

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?

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.

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.

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.

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.

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.

Enthusiasts often run out of leaves for caterpillars and rush to the nursery to buy more plants. Then comes the BIG question: How long should I test it with one caterpillar before placing more caterpillars/leaves together? You won’t like the answer.

First, to be 100% sure, until it becomes an adult and flies away without problem. If a caterpillar is exposed just before pupating, some insecticides won’t affect them until they emerge as adults. If some pupae are exposed, it won’t affect them until they emerge as adults. The adults will expand and dry their wings, but when they start to fly around, they go into spasms, usually eventually dying with their wings folded over their legs.

Next, at least into chrysalises. Some insecticides (such as used in some oral flea/tick medications) will affect them only when they begin to pupate. The result is deformed or incomplete chrysalises.

If you don’t have that much time and MUST feed the leaves to your caterpillars, wait three days if at all possible. The certified organic pesticide, Bt (a natural soil-dwelling bacteria), takes three days to do it’s job. Three days after caterpillars eat it, the caterpillars die.

Many insecticides will cause almost immediate vomiting (green fluid that stays green) and sometimes convulsions. This isn’t a pain reaction. It’s a nerve reaction. The insecticide acts on certain nerves, causing the caterpillars to jerk around.

Bottom line – the longer the better, up to the adult emerging and flying away.

For folks who live in Florida, Southern Texas, and below Tuscon, Arizona, your pipevine plants may be visited by two different swallowtail butterflies. This can cause a problem because most plants that Pipevine Swallowtail caterpillars can safely eat will kill Polydamas Swallowtail caterpillars and vice versa.

Now it’s a bit easier for you. Click here to visit our page that shows the difference in egg, larva, chrysalis, and adult forms of these two species.

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 New York or Oregon.

For the Southeastern US, these are some of the plants that would be great in a butterfly garden.

• Pawpaw for Zebra Swallowtail
• Pipevine for Pipevine Swallowtail
• Fennel, parsley, dill for Eastern Black Swallowtail
• Black cherry, tulip poplar for Eastern Tiger Swallowtail
• Spicebush, red bay, sassafrass, for Spicebush Swallowtail and Palamedes Swallowtail
• Milkweed for Monarch and Queen
• False nettle, hackberry, for Eastern Comma, Question Mark, Red Admiral
• Passion vine for Gulf Fritillary, Zebra Longwing, Variegated Fritillary, Julia
• Asters for Pearl Crescent
• Willow, hackberry for Mourning Cloak
• Willow, black cherry for Red-spotted Purple
• Willow for Viceroy
• Hackberry for Tawny Emperor and Hackberry Emperor
• Hackberry for American Snout
• Senna for Cloudless Sulphur, Orange-barred Sulphur, and Sleepy Orange

Many of these plants are available online from Shady Oak Butterfly Farm.

There is a concern expressed by enthusiasts who want to remove the head capsule from a molting/molted caterpillar. Should you? Or not?

There are two beliefs on this. One belief is that, if it molted and can’t get its head capsule off, an enthusiast should remove it to allow it to eat and grow. The other belief is that, if it didn’t take it off naturally, removing it and allowing it to live and lay mate may pass on a defective gene, one that may have interfered with the molting process.

There is a challenge to be sure that it has finished molting. Removing it too soon will kill it. If it has been observed molting and it has been a while with the head capsule still on its mouth, what do you think?

What are your thoughts? Please comment below.