Continental-scale host plant use by a specialist insect herbivore: Milkweeds
, cardenolides and the monarch butterfly, p.
Monarch caterpillars, which feed on plants in the milkweed
family, readily feast on Asclepias curassavica.
colonies in the Midwest have been emphasized as vital repopulation areas for monarchs (Wassenaar & Hobson 1998), with researchers calling for extensive habitat restoration in this region (Pleasants 2017; Thogmartin et al.
(43[degrees]57'N, 69[degrees]33'W), mostly from common milkweed
and pasture rose Rosa Carolina, with smaller numbers from ox-eye daisy Leucanthemum vulgare, common buttercup Ranunculus acris, cow vetch Vicia cracca and red clover Trifolium pratense.I sampled these adults independently of mass, but the sample size ensured that they included individuals likely to become among the earliest ovipositers.
Monarch caterpillars' sole food source is leaves of the milkweed
plant, a perennial flowering herb.
But roadside Northern pin oaks had about 50 percent more sodium than distant oaks, and milkweeds
, the main food for monarch butterfly caterpillars, could carry 30 times as much sodium as their kin that grow far from roads.
You can join in: Grow native milkweeds
in your garden (you can collect the fluffy seeds from roadsides in fall), count caterpillars on milkweeds
in or near your yard, record monarch migration dates, and turn your data into Monarch Watch at www.MonarchWatch.org.
Scientists attribute the decline of the migration in particular to the destruction of forests in Mexico and of breeding habitat in the US, to climate change and, above all, to the eradication of milkweed
, the plant on which monarchs lay their eggs and their larvae depend for food.
Agrawal, first author Kailen Mooney, who is a former Cornell postdoctoral researcher and now assistant professor at the University of California-Irvine, and colleagues studied trophic cascades in 16 milkweed
species, famed for their interactions with monarch butterflies, and also fed upon by aphids.
They sound innocent enough--called "pale swallow-wort" and "black swallow-wort," and both are members of the milkweed
"It looks like your tomato and potato plants were crowded out by thistles and milkweeds
and dandelions," he told Johnny.
isn't your average weed; in fact, I feel guilty calling it a weed at all.