I was asked a question last week about what white-lined sphinx moth caterpillars eat. I had read that they eat wild relatives of the four-o’clock, a garden plant. A few weeks ago we visited Boyce Thompson Arboretum State Park and I got some great first-hand information about what kind of plants the caterpillars feed on.
At the arboretum we found caterpillars on a native plant that is being used as a landscape perennial called pink guara (Guara lindeimeri). I noticed, however, the caterpillars were only eating the flowers. Often the flowers lack toxins or feeding deterrents found in the leaves or stems, although I don’t know for sure this is the case here.
Some of the caterpillars were working on a plant called white ratany (Krameria grayi).
I needed a friend’s help to identify that one. The plant has pretty purplish-pink flowers, but they are inconspicuous. She said the plant is a partial parasite that takes food from the roots of fellow desert plants like bursage or creosote bush. I also found out that the flowers produce an oily substance rather than nectar (weird!), but that some native bees will take it to mix with pollen.
Finally, we cheered the caterpillars when we found this batch eating the noxious weed, spotted spurge. Go white-lined caterpillars, go! (Sorry, the photo isn’t all that great).
For more information about white-lined sphinx moths and their caterpillars, check these previous posts:
Some of you might be wondering why the white-lined sphinx moth caterpillars (Hyleslineata) are traveling in such numbers (see previous post). No one knows for sure what is going on. Two suggestions are that the caterpillars are looking for places where they can dig into the soil to pupate, and/or that they have run out of food and are looking for more. The caterpillars feed on common desert weeds, several wild relatives of four o’clocks. These plants are drying out since we haven’t had rain in a little while, so it is possible at least some of them are looking for food.
I was able to do a small experiment to test whether the pupation idea holds water. If you place one of these wandering larvae in a terrarium filled with soft, moist potting soil, you will be amazed at how fast they dig in. I expected to see a bit of wandering, then dig into the soil. Nope, almost as soon as their legs touched the soil they were digging. The hard clay desert soil (yes, our desert soil is clay rather than sand) is almost like cement where these larvae were found.
Wow, talk about timing. Shortly after I posted my Bug of the Week yesterday suggesting white-lined sphinx moth caterpillars (Hyles lineata) might be coming soon (see after second ladybug in that post), I got a call that masses of caterpillars are crossing Maricopa Road just South of Riggs Road, near Maricopa, Arizona. I drove right down. I probably should have taken the video camera instead of my still camera, because it doesn’t do justice to how fast these caterpillars were moving.
Unlike the pictures I linked to yesterday, these are mostly yellow and black caterpillars with a greenish head. As with many sphinx moths, the caterpillars have a spike at the tail.
The yellow marks below are where caterpillars didn’t make it across the road. I hope you can make out the yellow squiggles of all the caterpillars that are trying.
White-lined sphinx moth caterpillars vary considerably in color. This one was pale green rather than bright yellow.
If all these recent posts about caterpillars have made you interested in butterflies and moths, here are some books where you can learn more.
Books about caterpillars/butterflies for the youngest bug enthusiasts (Toddler):
The Very Hungry Caterpillar by Eric Carle
Summary: The board book version of this story is a perennial favorite. The story line is fun, the illustrations are colorful and the holes in the pages are magnets for little fingers. We made stick puppet characters and performed the story again and again.
In depth review: As a scientist, I do have to point out one minor misuse of a term. In the end of the book (do I need to say spoiler alert here?) the caterpillar turns into a cocoon and then into a beautiful butterfly. Technically, however, a butterfly comes from chrysalis (or chrysalid), not a cocoon. Cocoons are the silken bags that moth caterpillars form around themselves prior to pupating. I see it as just a sloppy use of a word with a precise scientific meaning.
Eric Carle has been very open about admitting his mistake, although he does talk about an obscure butterfly that actually makes a cocoon. See http://www.eric-carle.com/q-cocoon.html for his response. To be fair, this book is a work of fiction. Caterpillars don’t really eat cherry pie or sausages either. That is part of what makes it so fun. So, go ahead and pick up a copy. You can read it as is, substitute chrysalis or substitute the word pupa if you don’t want to say chrysalis.
Caterpillar’s Wish by Mary Murphy is another colorful picture book about a caterpillar that turns into a butterfly. It is a delightful story about three friends. Bee and Ladybug can fly, but Caterpillar can’t. Caterpillar feels left out until he transforms into a butterfly.
In depth: Once again the author has chosen to call the transitional stage a cocoon. In this case it may be because cocoon is a smaller word, more appropriate for toddlers? (Perhaps authors of children’s books should use the more generic word “pupa.” It is short, easy to say and always correct, regardless of which insect is the subject.)
Inch by Inch by Leo Lionni is an adorable tale of an inchworm that escapes from some hungry birds in a clever way. This book could also be useful as an introduction to measuring.
Waiting for Wings by Lois Ehlert is bright, bold and beautifully done. It traces the life cycle of a butterfly very simply, and then has a bit more in depth information about butterflies and flowers at the end. There’s even a page of information about butterfly gardening.
From Caterpillar to Butterfly by Deborah Heiligman, and illustrated by Bari Weissman, is an account of a classroom caterpillar that undergoes metamorphosis into a beautiful butterfly.
Caterpillarology by Michael Elsohn Ross is for children who are interested in science and doing science experiments. This book (and the others in the “-ology” series) are chock full of great information and fun activities. Whereas many children’s books repeat the same information over and over, these books are truly unique and interesting. “Chosen by Science Books and Films as one of the Best Books for Children.” Unfortunately, they are often out of print and may be hard to find.