Newborn Milkweed Tussock Moth Larvae A Bonanza For Predatory Stink Bugs
Monarch larvae aren’t the only insects equipped to feed on the toxic cardiac glycoside-filled leaves of milkweed. Milkweed Tussock Moth larvae also dine on them, avoiding veins due to the latex-like, sticky white sap that could glue them in place. When they first hatch, Milkweed Tussock Moth larvae tend to stick together in “herds,” all feeding on the underside of the same leaf. This behavior provides a gold mine for predators such as predatory stink bugs (pictured) that discover them. Unlike their (plant) sap-sucking stink bug relatives, predatory stink bugs feed on more than 100 species of insect pests, often attacking insects much larger than themselves, drinking their body fluids with their needle-like beak. (Photo taken and kindly donated by Chris Doyle)
Milkweed Tussock Moths
Milkweed Tussock Moth caterpillars are responsible for eating all portions of milkweed leaves but the largest veins that contain sticky latex. They can tolerate the cardiac glycosides within the milkweed plant that are toxic to most other insects as well as certain mammals and birds. Like Monarchs, these caterpillars retain the toxic compounds as adults, and are therefore avoided by many predators.
Female Milkweed Tussock Moths lay their eggs in masses on the underside of milkweed and dogbane leaves, which their larvae will eat. The hatching caterpillars are gray and hairy, but in no time they have developed the tufts of hairs that give them their name. When fairly young, the larvae tend to stay together, skeletonizing the leaves they consume. As they mature, the caterpillars tend to wander, and it’s unusual to find large groups of them on a single leaf.
Many of the insects that feed on milkweed have orange and black patterns as both larvae and adults. These colors serve as a warning to would-be predators. One of the adult Milkweed Tussock Moth’s main predators is bats. While the moth possesses these colors during its larval stage, as a pale brown adult (the stage that nocturnal bats prey on them) it lacks the bright coloration (which would provide little protection in the dark) but has an organ that emits an ultrasonic signal easily detected by bats. The signal warns that an attack will be rewarded with a toxic and distasteful meal, thereby deterring predation.
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Milkweed Tussock Moth Caterpillars Feeding
Female milkweed tussock moths lay their eggs in masses on the underside of milkweed and dogbane leaves, which their larvae will eat. The hatching caterpillars are gray and hairy, but in no time they have developed the tufts of hairs that give them their name and make them resemble little mops. When still fairly young, the siblings stay together, skeletonizing the leaves they consume, leaving only the strongest veins that contain sticky latex. As they mature, the caterpillars tend to wander, and it’s unusual to find large groups of them on a single leaf. At this point they often cut through a vein in order to prevent the latex from reaching the area of the leaf where they are feeding. (Older monarch caterpillars use this same tactic.) Like monarchs, milkweed tussock moths, because they’ve consumed the cardiac glycosides contained in milkweed and dogbane leaves, are toxic to predators.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
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