Caterpillars

Seahorse

Active Member
Was at the beach yesterday near Laguna Del Mar and saw hundreds of caterpillers coming over the sand dunes and heading out to the sand flats to the ocean, it was low tide. My husband walked the dog out to the water and he said they were all the way out there too. Some were orange and black and some were yellow and black. They were from one inch to 5 inches long, some were as wide as a pencil and others as wide as your finger. We were loading up the beach chairs and notice some were heading back to the desert while other still heading to the ocean. Also noticed no seagulls or shorebirds eating them. Has anyone ever seen this before or know what kind of butterfly they will become?
 

Jungle Jim

Well Known Member
Hey Horse......

They are the larvae of the White Lined Sphinx Moth. Their preferred food is the Sand Dune Primrose and the Sand Verbena. When they eat themselves out of house and home they go into a migration mode searching for greener pastures. You might notice them being followed by a large black carnivorous beetle, a type of Ground Beetle of the genus Carabidae, specifically the Calosomas or Searchers. You might even notice their larvae following as well. These are up to 2 1/2 inches long, black and fuzzy with all six legs up front that look like giant Lady Bird Beetle larvae. Both adults and larvae literally tear the caterpillars to shreds with their powerful jaws. The adult beetles are powerful flyers and actively search at night for new populations of the Sphinx Moth larvae. When stomped on they smell like an over ripe apricot.

The Sphinx Moths and the Calosomas have been waiting underground as pupas and only emerge when this wet winters rains brought out the wildflowers. The moths emerge, mate, feed on the flowers, lay thousands of eggs then migrate north in search of more flower fields. This past few weeks I've been seeing dozens of them every night feeding on my blooming citrus trees. They are probably the parents of the caterpillars that you saw. The White Lined Sphinx, the Calosoma and the Painted Lady Butterfly conduct an incredible type migration known as a "Leap Frog Migration". They are following the wildflower bloom northwards. Each local population will move a hundred miles or so then their offspring will emerge and fly another hundred miles. In the case of the Painted Lady the leap frogging will take the species over three thousand miles from Mexico to Canada. No one individual is capable of the complete journey.

JJ
 

Seahorse

Active Member
You are right JJ. I have been looking at google caterpillar images and found it. The colors must be different phases and the strips are head to the end of the body, not circular around the body like the monarch butterfly caterpillar. They are also called the Hummingbird moth as they look like a hummingbird. We had them at our old house, but I had never seen the caterpillar stage. It was quite a thing to see so many and going out on the sand flats at low tide.
 

Jungle Jim

Well Known Member
Also............

The White Lined Sphinx caterpillar is available in two flavors, lime green and flat black with a variety of stripes and sprinkles in between. This is an adaptation that allows the youngster to survive in the cold winter months or the hot months of late spring into early summer and even a summer monsoon situation. They can emerge as flying adults any time of the year after a good rainfall to coincide with the winter or summer annual wildflower germination. During the winter when in many desert areas nighttime temps drop to close to freezing the flat black babies absorb the heat from the sun in the mornings and are ready too feed before the green guys can. In the late spring, early summer and monsoon the light green babies reflect the unwanted heat while the black version is killed by overheating. So, the species has evolved in a way to always insure the some of the young will survive no matter if it's too hot or too cold.

We have two other Sphinx Moths here in our deserts, the well known Tomato Hornworm Sphinx Moth and the Tobacco Hornworm Sphinx Moth. Almost anyone who has homegrown tomatoes has seen those big green larvae stripping the leaves from their plants. The adult moth is double the size of the White Lined variety. The tobacco variety is less likely to be noticed because it's preferred food here is the poisonous Jimson Weed or Datura that usually grows as a roadside weed or in the larger desert washes. The tobacco variety is the largest Sphinx Moth in our area with a wingspan of five inches or more. Funny thing though, I have the local Desert Tobacco and the Tree Tobacco plants in my yard as well as Jimson Weed but I never see the larvae feeding on the tobacco plants but the adult moth feeds on all three plants. The green larvae of the tobacco variety is huge, over six inches long and almost an inch in diameter.

Out here in the Imperial Sand Dunes the poop of the White Lined variety dries up into rock hard pellets about 3/8" long and 1/4" diameter. Long after the Primroses and Verbenia have dried up and gone their way those caterpillar poops get windblown into vast windrows the persist for years. When things warm up and our lizards wake up to a windfall of juicy gusanos they just pig out. I've seen Desert Iguanas, Chuckwallas and Collard Lizards with their faces completely covered with green worm spit.

JJ
 
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