By Wendy Langhans
Did you give your kids a vitamin pill this morning? If so, you’re not alone; according to a 2007 news report , almost 1 in 3 childen in the US take a dietary supplement. But it might surprise you to learn that humans are not the only creatures that medicate their children. Monarch Butterflies may use a chemical found in milkweed to protect their offspring from parasites.
About 30 percent of western Monarch Butterflies carry a parasite in their gut. When females lay their eggs, this protazoan parasite, “Ophryocystis elektroscirrha”, can be passed on to their offspring. “If the adult butterfly leaves the pupal stage with a severe parasitic infection, it begins oozing fluids from its body and dies (see photo ). Even if the butterfly survives, it does not fly as well or live as long as uninfected ones.”
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As we learned in school, the larvae of monarch butterfly larvae eat milkweed leaves. These leaves contain toxic steriods, known as cardenolides, that gives the milkweed larvae and butterfly a bitter taste which discourages predators . Here in the mountains of Southern California, we have three species of Milkweed: Narrow-leaved Milkweed (Asclepias fascicularis), Indian Milkweed (Asclepias eriocarpa) and California Milkweed (Asclepias californica). Each species contains a different concentration of cardenolides, with Indian milkweed carrying the highest concentration (>400 ug/ 0.1 mg plant material).
Recently, researchers at Emory University  found that eating milkweed species containing higher concentrations of cardenolides, “can reduce parasite infection in the monarchs”. They also discovered that, in a labratory setting, parasite-infested female monarch butterflies choose to lay their eggs on milkweed plants with a higher concentration of cardenolides. In other words, female monarch butterflies chose to “lay their egg on plants that will make their offspring less sick”.
More research is needed, to find which chemical actually reduces parasite infestion. (And just maybe, to see if monarch larvae prefer bear-shaped gummies over other chewables?)
Upcoming Outdoor Events:
Saturday, October 16, 8-10 AM, Birding Hike at Towsley Canyon. For directions and trail maps, click here .
Friday, October 22, 6:30-8:30 PM, Things that go bump in the night at Towsley Canyon. Everything changes when the hunters become the hunted and the blind become the seeing. For directions and trail maps, click here .
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at email@example.com  for time and place.
Wednesday mornings, October 6, 13, 20, & 27.
Saturday mornings, October 9 & 23.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
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