The white Satin Moth looks like an angel, but in large numbers, it spells impending trouble for poplars and willows.
Satin Moths are completely white with an exception for their legs. Their legs are checkered in black and white. It seems inconceivable that such a lovely, satiny moth would cause problems, but this species gives rise to many hungry caterpillars. Satin Moth caterpillars are voracious eaters of poplar and willow leaves, and after an initial round of feeding in the spring, more come back in late summer. They eat tree leaves, leaving only the main vein and petiole behind. This damage is visible as more sunlight gets through to the ground, and the tree canopy starts to look like it is disappearing. Heavy feeding in the early summer by a large number of caterpillars can completely defoliate a tree. Without leaves, a tree must resort to its food stores to survive until a new batch of leaves can grow. Unfortunately, by the time new leaves grow, another batch of larvae hatch and eat away at them, though not as vigorously as the early generation. After a few years of this level of stress, trees die.
Satin Moth adults emerge in summer. Males and females mate in mid-summer, and females lay light green eggs in oval-shaped groupings on leaves and branches among the poplar trees. About a month later, these eggs hatch and larvae begin to feed on leaves until they prepare for winter. They move to the tree trunk and wrap silk around themselves to protect them from the cold winter months. They emerge from these cocoons in spring to continue eating and developing. It is this group of caterpillars that does the heavy damage to tree foliage. Once they have matured enough, they pupate, becoming a new generation of adults that produce offspring in late summer. There is no way to keep Satin Moths from accessing poplar trees. Maintaining superior tree health and introducing natural predators to the area may help reduce tree defoliation and stress. Certain insecticides that are sprayed in the spring, when the caterpillars are coming out of hibernation, can also aid in limiting damage.
Satin Moths can form large populations and adults are attracted to lights. They may cluster in an area so closely that they look like a blanket of snow. Caterpillars are 35-40 mm (1.5 inches) long and have black bodies with large pale yellow/white dots on their dorsal (spine) side. Each pale spot is flanked on both sides with a round, red bump. Red bumps also run down toward the ventral side by the feet. Yellow tufts of spiky hairs protrude from them. They may be seen crawling around the ground as they move to other trees. They may also roll leaves and secure them with silk to form a retreat in which to pupate.
Scientific Name: Leucoma salicis
Butterfly or Moth
Size (Adult; Length): 24mm to 50mm (0.94in to 1.95in)
Colors: white, black
Descriptors: satin, sheen, shiny, glossy, flying, destructive, pest, checkered legs
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Butterfly and Moth Anatomy
Antennae: Butterflies and Moths have a pair of antennae on the head used as sensors.
Head: The head is home to the insect's eyes, antennae, and proboscis.
Thorax: Home to the three pairs of legs as well as vital internal organs.
Abdomen: Contains vital internal organs such as the heart(s) and reproduction facilities.
Forewing: The upper, forward wing pair used for flying.
Hindwing: The lower, rearward wing pair used for flying.
NOTE: Butterflies and Moths are part of the Lepidopteran order as they share many similarities.