21 July 2010

critters: Hawkmoths Munch the Datura

After I posted this about letting a big ol' Manduca sexta tobacco hornworm devour my tomato plant, I learned from a reader Paul that the hornworms - the larvae of hawkmoths in the family Sphingidae - love datura as well. He said that he picks them off his tomatoes and relocates them to datura. That makes sense, because datura and tomatoes are both nighshades in the family Solanaceae.

Solanaceae is big plant family that includes lots of common plants that we know, from tomato, potato, and chili pepper to datura, tobacco and petunia. So, if a hawkmoth evolves a way to handle the poisonous defenses of plants in the nightshade family, it would make sense that it might be able to eat others of the same family.

After Paul's comment, I kept an eye on my datura plants, of which I have 3. One day, I saw that one of the datura plants in front was being completely devoured by hawkmoth larvae. It probably had about 10 of them at minimum! And I'd identify these again as the common Manduca sexta because of the white stripes and the orange horn.

Here one is munching away.

Frass on leaves is a telltale sign of the critters and can help me find them (poop falls straight down, in other words).

This is what the plant looked like when they were finished. Completely stripped!

But the datura has sense grown new leaves and even supported another (smaller) crop of hornworms. Now, if the caterpillars would only give the plant a chance to produce enough energy to bloom. Then, when they become adult moths, they'll have some nectar to sip on.

It's cool that the datura can support both the larval and adult forms of this amazing insect.

Site plug: Here's a great website for identifying hawkmoth larvae in the Central Texas area. Oh, and my original photo of the Manduca sexta made an appearance on Central Texas Gardener. Thanks Linda!


Birdwoman said...

I'm a contrarian gardener who enjoys hornworms. They are fascinating critters. I found one on one of my brugmansias last year which was the first time I had become aware that they did feed on brugs or datura, but, as you say, nightshade family...duh!

BiscottiQueen said...

I can see your fascination with them, but I am yet to let them devour a precious tomato plant. I have decided to relocate our hookworm caterpillars over to the chicken coop's run. The birds seems satisfied with the gifts.