|Monarch sharing a pitcher sage plant with a bumble bee|
|Monarch Fall Migration, from USFS pollinator site |
Unlike the Methuselah-monarchs bent on the southern horizon in the fall, the spring migration requires multiple lifetimes . They drift northward over 3 or 4 generations. It appears to be these shorter lived summer monarchs that are the sink of the decreasing monarch brood. For years people blamed declining populations on habitat loss in the monarch wintering roosts in Mexican forests. Recent studies suggest that it is actually the Midwest's ultra-efficient weed control in the summer breeding grounds that is at the root of the decline. Monarchs simply can't find enough milkweed on which to lay their eggs.
|Asclepias asperula, antelope horns/spider milkweed|
A. linearis (likely endemic to Texas)
A. texana (endemic to Texas)
* denotes documented larval host to monarch caterpillars 
It is possible that some of the milkweeds that have not been documented as larval host plants have successfully nourished monarch brood. Some, like the Texas endemic Asclepias texana, are relatively uncommon and are less likely to be observed, period. I'm a bit of a plant collector so I'm going to try to get my hands on some native milkweed seed to sow this winter. In the spring, after receiving the cold/moist stratification they require in my fallow garden, these seeds should emerge and start my monarch buffet. Eventually my plants will provide high-quality nectar to monarch butterflies on their way north, and leafy lunches to little monarch caterpillars beefing up for their transformation and long journey.
As an FYI to any North Texas readers: this week is the Fort Worth Botanic Garden's fall plant sale. I have not confirmed that they will be selling milkweed, but considering their focus on native plants and insects I think it is fairly likely. The plant sale starts the evening of Friday, October 9th and goes through October 11th. You can find more information here.
Good bye monarchs, at least until March next year!