Remember the green caterpillar that showed us its trachea and heart?

It has been going through some changes.

One morning it looked like this. No worries though.

There's nothing wrong with it. The green caterpillar has entered the phase of the life cycle called the prepupa. It was ready to change into a pupa.

Sure enough, the next day it had pupated. Can't wait to see what the moth looks like.

Too bad the pupa isn't see-through like the caterpillar was, so we could see the changes happening inside.

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Aside:  Every year we expect to hear cicadas around Father's Day. Sure enough, Father's Day was Sunday and we heard our first cicada on Monday. Talk about sticking to a calendar!

Remember the see-through green caterpillar from last week? I've been studying it some more.

After discovering the air passages or trachea were visible through the exoskeleton, I decided to look for other internal features.

What about the dark green line in the middle of the back? (Photograph was taken looking down at the caterpillar.)

You might think that was the intestine, but I happen to know that the "heart" in insects is a long tube running through the dorsal surface (back). Could that be the "heart?"

Let's take a look at this video taken from the perspective looking down at the caterpillar from the rear. Watch the green line.

 

If you look closely, you should be able to see the vessel expand and contract as hemolymph (the insect version of blood) is pumped through.

You might also notice that the pumping is not regular. It starts and stops.

The circulatory system in insects consists of a long tube called the dorsal vessel. The part running through the abdomen is designated as the heart.The aorta is located in the thorax and head.

Unlike ours, it is an open system. The hemolymph bathes the tissues inside the insect. When the heart pumps, the hemolymph moves into the dorsal vessel from the posterior or rear of the caterpillar and flows toward the head end.

Once in the dorsal vessel, the hemolymph exits through openings known as ostia. There the hemolymph goes back into the tissues, carrying in nutrients and moving away wastes.

It was pretty cool to see something I'd learned about in textbooks pumping away in real life.

Have you ever seen an insect heart in action?

Want to learn more? Try this article about the circulatory system in insects at North Carolina State.

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Toads are fascinating animals that are too often ignored. The new picture book, The Hidden Life of a Toad* by biologist and photographer Doug Wechsler, brings attention to these neglected creatures.

(*Amazon Affiliate link)

The main text concentrates on toad development and life cycle, complete with photographs of toads mating. Back matter is filled with supplemental information, including a glossary, toad facts, suggestions for helping toads, and details about how the author captured the photographs.

For my full review, see Nonfiction Monday blog.

Related:

Is it a Frog or Toad?

The terms "frog" and "toad" are not scientifically-based, but are common names. According to frog scientists, all frogs and toads belong to the Order Anura and are called "frogs." Although many people call the bumpy, dry land-dwelling creatures "toads" and the smooth-skinned, pond-dwelling creatures "frogs," in reality some species are hard to separate into one or the other group.

This brown, bumpy animal is a toad.

Toad External Anatomy

Have you ever taken a close look at a toad? You may discover some interesting things.

(Illustration based on public domain photo from Visual Hunt)

Starting with the head, prominent features are the bulging eyes. Because they are nocturnal, toads have well-developed night vision. A cool fact is that frogs and toads use their eyes to push food down their throat when swallowing. If you aren't put off by seeing frogs eating bugs, there's a video of frogs swallowing from David Attenborough.

Adult toads have lungs and breathe through opening called nares.

Fun fact:  Toads don't drink water through their mouths, but absorb water through their skin by sitting in it.

Beneath the mouth, male toads have a flexible membrane called a vocal sac. The sac helps amplify the mating calls.

The circular tympanum has a dual function, serving to pass sound vibrations into the ear and also as a protective cover.

Large bumps on the back behind the head, the parotoid glands of toads produce toxic secretions. This is why you should keep pets away from toads and wash your hands after touching them.

A toad has four toes on their forelimbs (front legs) and five toes on the back. Unlike frogs, toads lack webbing between their toes. Both frog and toads are known for their ability to jump with their hind legs.

A .pdf worksheet (with blanks) to download:  toad external anatomy worksheet

Toad Life Cycle

Toads also lay their eggs in water and the eggs hatch into tadpoles.

The dark-colored dots are the frog embryos. They are protected by a gooey jelly-like substance.

The embryos grow into free-swimming tadpoles. They feed and grow, eventually developing legs. Once the tadpoles grow lungs they can move onto land and they are called "toadlets." During that time, their tail disappears.

Activity: Life Cycle Poster

Gather:

  • Pictures of frog and toad life stages from books or the internet
  • Art supplies such as markers, crayons, colored pencils, and/or paint
  • Large sheets of paper

Encourage the children to plan and decorate a poster featuring the stages of a frog or toad life cycle. Don't forget the toadlet stage.

Younger children might benefit from exploring life stage models.

Insect Lore Frog Life Cycle Stages

Where Adult Toads Live

Toads feed on insects and other small creepy crawlies. During the day they rest in moist, shady places. Growing some dense shrubby plants will provide them with cover.

Activity:  Make a Toad House

Instructions for making toad houses are all over the internet. Here are directions for a simple version.

Gather:

  • Clay flower pot at least six inches in diameter
  • Two potato-sized stones
  • Optional:  Acrylic paints and paint brushes

If you desire, have the children decorate the flower pot with acrylic paint. Acrylic markers work, too. Precautions:  Prior to painting, protect the work surface with a washable or disposable covering.

Once the paint is dry, find a moist, shady location outdoors. Overturn the pot and use the two stones to prop up one side. Leave enough room between so a toad can climb under. Make sure the toad house is stable, so it won't slip off the stones and trap the toad inside. Burying it slightly on the back side or covering the back side with a small amount of soil may help stabilize it.

Providing a small tray of water nearby will help keep the area moist. Keep curious pets away and check regularly.

Interested in learning more? See our growing list of children's books about frogs and toads at Science Books for Kids.