The white-lined sphinx moth, also known as a hawk or hum­ming­bird moth, can be found in Anza Bor­rego in the spring and after sum­mer mon­soon rains. It is a fair­ly com­mon moth with a range from Cen­tral Amer­i­ca to Cana­da. Most peo­ple vis­it­ing the desert see the cater­pil­lar form, which vora­cious­ly eats some of the desert annu­al flow­ers dur­ing the day­time. It most prefers to eat the dune evening prim­rose and brown-eyed prim­rose plants, which are plen­ti­ful annu­als after a rainy win­ter. The cater­pil­lars grow quick­ly and can reach 5 inch­es in length. Their mark­ings vary, but most of the ones in Anza Bor­rego are a mix of green and black; they range from almost all black to a mix of black and green stripes to the more rare most­ly green form. The larg­er cater­pil­lars can move quick­ly and will cross roads when look­ing for food. Once they are mature, the cater­pil­lar digs a shal­low hole in the sand by mov­ing its upper body back and forth. It then pupates under­ground, with the sand pro­vid­ing pro­tec­tion while it waits for the right con­di­tions to wrig­gle up from the ground and emerge as a moth. The adult moths most­ly fly from dusk to dawn and look like a grey blur with a plump body and fast wings that hov­ers by a flower to feed before fly­ing off to the next plant. From a dis­tance they look like a tiny hum­ming­bird. Both the moths and the cater­pil­lars can car­ry pollen between flow­ers, help­ing to pol­li­nate the plants and start the next generation.

Dur­ing pro­lif­ic years, there can be hun­dreds of thou­sands of cater­pil­lars in the area north­west of Bor­rego Springs, such as off of DiGior­gio Canyon Road and Hen­der­son Canyon Road. They will quick­ly eat the prim­rose plants before mov­ing to the next area. As each female moth can lay hun­dreds of eggs, it does­n’t take very many moths to pro­duce this many cater­pil­lars. The migrat­ing Swain­son’s Hawks and rep­tiles will eat the cater­pil­lars, but dur­ing pro­lif­ic years this prob­a­bly does not great­ly reduce the cater­pil­lar population.

Click on any pho­to for full-size image, then back but­ton to return. Pho­tos and cap­tions by Bar­bara Swanson.

White-lined sphinx moth cater­pil­larA cater­pil­lar for­ages on a brown-eyed prim­rose plant.

Cater­pil­lar look­ing into sun­setA cater­pil­lar rests on a desert sun­flower branch as sun­set approaches.

An elu­sive moth to pho­to­graphLook care­ful­ly at the low­er left prim­rose flower. The white-lined sphinx moths come out at dusk to feed on nec­tar. It looks like a small hum­ming­bird as it hov­ers. As it goes from flower to flower it pol­li­nates the flow­ers, help­ing to ensure the next gen­er­a­tion of plant and insect.

Sphinx moth cater­pil­lar after a rain­stormA close-up of a cater­pil­lar sit­ting on a brown-eyed prim­rose after a rainstorm.

Cater­pil­lars on an evening prim­roseAbout two dozen cater­pil­lars have a feast on a dune evening prim­rose plant. While eat­ing most of the leaves they leave fer­til­iz­er for the next gen­er­a­tion of plants.

Cater­pil­lar in the morn­ing lightAfter the morn­ing tem­per­a­ture warmed up the cater­pil­lars went search­ing for food. This cater­pil­lar walks up a dune, adding its tracks to those who already trav­eled this way.

Cater­pil­lar trailsThe side of this dune looked like it was a cater­pil­lar highway.

Emerged from the sandWhen the pupae have matured they wrig­gled to the sur­face and then emerge as the moth. I found this one in the morn­ing. If you look close­ly you can see the abdomen (on the right) and the feet (on the left) of the moth through the out­er pro­tec­tive layer.

Cater­pil­lar treatA cater­pil­lar eats a dune evening prim­rose flower.

A cater­pil­lar bedAs the evening tem­per­a­ture dropped, this cater­pil­lar set­tled in for the night on a dune evening prim­rose flower bud.