|The Question: I’ve looked through all my insect books, including those that specialize in New England insects, and can’t even identify this species. I’m a rank amateur, but usually can get that far. I saw quite a few of them this summer and didn’t anticipate such a problem! Jeepers, I’m so glad I found this blog!
Submitted by: Martha, Massachusetts, USA
The Short Answer: Martha, thanks for your excitement at finding AskaNaturalist.com. We’re glad to have you as a reader! And what you found is a yellow-collared scape moth (Cisseps fulvicollis), one of a large family (Arctiidae) of moths that as a group are called tiger moths. Cisseps fulvicollis is a common species, found throughout North America. Despite the yellow in its name, the yellow-collared scape moth sports what is clearly a bright orange collar. Like many brightly colored animals, and like most tiger moths, the yellow-collared scape moth tastes bad to predators. The bright colors are an example of “aposematism,” a survival tactic where by advertising your unpalatability, you increase the chance for survival of your relatives. Imagine that a bird tries to eat a yellow-collared scape moth and discovers that it tastes bad. The bird’s discovery may come too late for that moth, but once educated, that bird is less likely to attack any of that moth’s close relatives, who also carry the same bright coloration. In this way, the genes for the bright coloration gain a survival advantage.
To make themselves unpalatable, yellow-collared scape moth caterpillars feed on plants that carry pyrrolizidine alkaloids (PAs). These substances are generally distasteful and mildly poisonous. Plants use them to discourage grazing by mammals and other plant eaters. But yellow-collared scape moths and other tiger moths are generally not affected by PAs. In fact, males release PAs as a sexual attractant when it’s time to mate. By showing how much PAs they carry, the males are proving to females how healthy – and distasteful to predators – they are. This is important because the male transfers some of his PAs to the female when he deposits a sperm package during mating. The poisonous PAs in the sperm pack are then incorporated into the eggs, giving them protection from predation.
For more information on yellow-collared scape moths, go to: http://pnwmoths.biol.wwu.edu/browse/family-erebidae/subfamily-arctiinae/tribe-arctiini/cisseps/cisseps-fulvicollis/
More Information – This is Cool!: Visual aposematism is very common in the natural world. Most people have heard that lady bugs are brightly colored because they taste bad. Poison dart frogs advertise that they are off limits to predators. Even the white and black patterning of a skunk can be considered to be visual aposematism.
But there are other ways to advertise your noxiousness to predators, and tiger moths present a great example. Since most tiger moths are nocturnal, their main predators are bats. Bats, of course, don’t locate their prey at night by sight, so bright coloration to warn of noxiousness is useless. Bats hunt by using echolocation. They send out sound waves, and by sensing the sounds that bounce back from objects in the air, they can “see” what the object is and track its motion. But moths are not helpless in this process. Most moths have some way of hearing the echolocation of bats and taking evasive action. And some noxious tasting moths have evolved another response.
Dr. Aaron Corcoran at Wake Forest University, who studies the sounds moths make in response to bats, describes what happens. “The tiger moths wait until they have been detected by the bat and are being targeted. Then they transmit a warning signal that serves the same function as bright warning colors. Once the bat hears the signal it veers off, wanting no part of a noxious moth.”
It’s been shown that the first time a bat hears the warning sound, it ignores it and captures the moth. It usually then drops the moth, presumably after tasting it and saying, “Yuck!” Once a bat has associated the warning signal from the moths with the disgusting taste, it will avoid that type of moth in the future.
Dr. Corcoran also points out that just as some tasty animals have evolved coloring that imitates that of noxious animals in a phenomenon called Batesian Mimicry, “Some moths that are actually palatable to the bats make sounds that are similar to the sounds the toxic moths make. This often fools bats into avoiding a perfectly tasty moth.” (For more on visual warning signals and Batesian mimicry, go to http://askanaturalist.com/what-is-this-orange-backed-spider/)
This is Even More Cool!: Some moths have taken the life or death game one step further. When they hear an echolocating bat, they wait until the bat is very close and then they begin making a loud “white noise” that confuses the bat and makes it difficult for it to judge where the moth is at the last second. This causes the bat to miss and allows the moth to escape. This is very similar to radar jamming done by military jets trying to avoid detection.
Here are two YouTube videos that show this in action. In the first, the moth’s sound producing organs have been disabled. You’ll hear the bat echolocating and see that it catches the moth. The second video is the same species of bat and moth, but the moth in this case has not been disabled. Just as the bat approaches, you’ll hear a new buzzing noise, which is coming from the moth, and then the bat misses. Very cool.
Without jamming – https://www.youtube.com/watch?v=Qgq12GJV-qA
With jamming – https://www.youtube.com/watch?v=vrZ2hNZsCuE
For more on jamming of bats by moths, go to Dr. Corcoran’s website: http://www.sonarjamming.com/.
Landolt, PJ, & Phillips, TW. (1997). Host plant influences on sex pheromone behavior of phytophagous insects. Annual Review of Entomology, 42, 371-391.
Conner, W. E., and A. J. Corcoran 2012. Sound strategies: the 65-million-year-old battle between bats and insects. Annual Review of Entomology. 57: 21-39.